blob: 8812d8e35f5b03b13e148ff67ae33453cad306c1 [file] [log] [blame]
/*
* Performance events core code:
*
* Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
* Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar
* Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
* Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
*
* For licensing details see kernel-base/COPYING
*/
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/cpu.h>
#include <linux/smp.h>
#include <linux/idr.h>
#include <linux/file.h>
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/hash.h>
#include <linux/tick.h>
#include <linux/sysfs.h>
#include <linux/dcache.h>
#include <linux/percpu.h>
#include <linux/ptrace.h>
#include <linux/reboot.h>
#include <linux/vmstat.h>
#include <linux/device.h>
#include <linux/export.h>
#include <linux/vmalloc.h>
#include <linux/hardirq.h>
#include <linux/rculist.h>
#include <linux/uaccess.h>
#include <linux/syscalls.h>
#include <linux/anon_inodes.h>
#include <linux/kernel_stat.h>
#include <linux/perf_event.h>
#include <linux/ftrace_event.h>
#include <linux/hw_breakpoint.h>
#include <linux/mm_types.h>
#include <linux/cgroup.h>
#include <linux/module.h>
#include <linux/mman.h>
#include <linux/compat.h>
#include "internal.h"
#include <asm/irq_regs.h>
static struct workqueue_struct *perf_wq;
struct remote_function_call {
struct task_struct *p;
int (*func)(void *info);
void *info;
int ret;
};
static void remote_function(void *data)
{
struct remote_function_call *tfc = data;
struct task_struct *p = tfc->p;
if (p) {
tfc->ret = -EAGAIN;
if (task_cpu(p) != smp_processor_id() || !task_curr(p))
return;
}
tfc->ret = tfc->func(tfc->info);
}
/**
* task_function_call - call a function on the cpu on which a task runs
* @p: the task to evaluate
* @func: the function to be called
* @info: the function call argument
*
* Calls the function @func when the task is currently running. This might
* be on the current CPU, which just calls the function directly
*
* returns: @func return value, or
* -ESRCH - when the process isn't running
* -EAGAIN - when the process moved away
*/
static int
task_function_call(struct task_struct *p, int (*func) (void *info), void *info)
{
struct remote_function_call data = {
.p = p,
.func = func,
.info = info,
.ret = -ESRCH, /* No such (running) process */
};
if (task_curr(p))
smp_call_function_single(task_cpu(p), remote_function, &data, 1);
return data.ret;
}
/**
* cpu_function_call - call a function on the cpu
* @func: the function to be called
* @info: the function call argument
*
* Calls the function @func on the remote cpu.
*
* returns: @func return value or -ENXIO when the cpu is offline
*/
static int cpu_function_call(int cpu, int (*func) (void *info), void *info)
{
struct remote_function_call data = {
.p = NULL,
.func = func,
.info = info,
.ret = -ENXIO, /* No such CPU */
};
smp_call_function_single(cpu, remote_function, &data, 1);
return data.ret;
}
#define EVENT_OWNER_KERNEL ((void *) -1)
static bool is_kernel_event(struct perf_event *event)
{
return event->owner == EVENT_OWNER_KERNEL;
}
#define PERF_FLAG_ALL (PERF_FLAG_FD_NO_GROUP |\
PERF_FLAG_FD_OUTPUT |\
PERF_FLAG_PID_CGROUP |\
PERF_FLAG_FD_CLOEXEC)
/*
* branch priv levels that need permission checks
*/
#define PERF_SAMPLE_BRANCH_PERM_PLM \
(PERF_SAMPLE_BRANCH_KERNEL |\
PERF_SAMPLE_BRANCH_HV)
enum event_type_t {
EVENT_FLEXIBLE = 0x1,
EVENT_PINNED = 0x2,
EVENT_ALL = EVENT_FLEXIBLE | EVENT_PINNED,
};
/*
* perf_sched_events : >0 events exist
* perf_cgroup_events: >0 per-cpu cgroup events exist on this cpu
*/
struct static_key_deferred perf_sched_events __read_mostly;
static DEFINE_PER_CPU(atomic_t, perf_cgroup_events);
static DEFINE_PER_CPU(atomic_t, perf_branch_stack_events);
static atomic_t nr_mmap_events __read_mostly;
static atomic_t nr_comm_events __read_mostly;
static atomic_t nr_task_events __read_mostly;
static atomic_t nr_freq_events __read_mostly;
static LIST_HEAD(pmus);
static DEFINE_MUTEX(pmus_lock);
static struct srcu_struct pmus_srcu;
/*
* perf event paranoia level:
* -1 - not paranoid at all
* 0 - disallow raw tracepoint access for unpriv
* 1 - disallow cpu events for unpriv
* 2 - disallow kernel profiling for unpriv
*/
int sysctl_perf_event_paranoid __read_mostly = 1;
/* Minimum for 512 kiB + 1 user control page */
int sysctl_perf_event_mlock __read_mostly = 512 + (PAGE_SIZE / 1024); /* 'free' kiB per user */
/*
* max perf event sample rate
*/
#define DEFAULT_MAX_SAMPLE_RATE 100000
#define DEFAULT_SAMPLE_PERIOD_NS (NSEC_PER_SEC / DEFAULT_MAX_SAMPLE_RATE)
#define DEFAULT_CPU_TIME_MAX_PERCENT 25
int sysctl_perf_event_sample_rate __read_mostly = DEFAULT_MAX_SAMPLE_RATE;
static int max_samples_per_tick __read_mostly = DIV_ROUND_UP(DEFAULT_MAX_SAMPLE_RATE, HZ);
static int perf_sample_period_ns __read_mostly = DEFAULT_SAMPLE_PERIOD_NS;
static int perf_sample_allowed_ns __read_mostly =
DEFAULT_SAMPLE_PERIOD_NS * DEFAULT_CPU_TIME_MAX_PERCENT / 100;
void update_perf_cpu_limits(void)
{
u64 tmp = perf_sample_period_ns;
tmp *= sysctl_perf_cpu_time_max_percent;
do_div(tmp, 100);
ACCESS_ONCE(perf_sample_allowed_ns) = tmp;
}
static int perf_rotate_context(struct perf_cpu_context *cpuctx);
int perf_proc_update_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos)
{
int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
if (ret || !write)
return ret;
max_samples_per_tick = DIV_ROUND_UP(sysctl_perf_event_sample_rate, HZ);
perf_sample_period_ns = NSEC_PER_SEC / sysctl_perf_event_sample_rate;
update_perf_cpu_limits();
return 0;
}
int sysctl_perf_cpu_time_max_percent __read_mostly = DEFAULT_CPU_TIME_MAX_PERCENT;
int perf_cpu_time_max_percent_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos)
{
int ret = proc_dointvec(table, write, buffer, lenp, ppos);
if (ret || !write)
return ret;
update_perf_cpu_limits();
return 0;
}
/*
* perf samples are done in some very critical code paths (NMIs).
* If they take too much CPU time, the system can lock up and not
* get any real work done. This will drop the sample rate when
* we detect that events are taking too long.
*/
#define NR_ACCUMULATED_SAMPLES 128
static DEFINE_PER_CPU(u64, running_sample_length);
static void perf_duration_warn(struct irq_work *w)
{
u64 allowed_ns = ACCESS_ONCE(perf_sample_allowed_ns);
u64 avg_local_sample_len;
u64 local_samples_len;
local_samples_len = __this_cpu_read(running_sample_length);
avg_local_sample_len = local_samples_len/NR_ACCUMULATED_SAMPLES;
printk_ratelimited(KERN_WARNING
"perf interrupt took too long (%lld > %lld), lowering "
"kernel.perf_event_max_sample_rate to %d\n",
avg_local_sample_len, allowed_ns >> 1,
sysctl_perf_event_sample_rate);
}
static DEFINE_IRQ_WORK(perf_duration_work, perf_duration_warn);
void perf_sample_event_took(u64 sample_len_ns)
{
u64 allowed_ns = ACCESS_ONCE(perf_sample_allowed_ns);
u64 avg_local_sample_len;
u64 local_samples_len;
if (allowed_ns == 0)
return;
/* decay the counter by 1 average sample */
local_samples_len = __this_cpu_read(running_sample_length);
local_samples_len -= local_samples_len/NR_ACCUMULATED_SAMPLES;
local_samples_len += sample_len_ns;
__this_cpu_write(running_sample_length, local_samples_len);
/*
* note: this will be biased artifically low until we have
* seen NR_ACCUMULATED_SAMPLES. Doing it this way keeps us
* from having to maintain a count.
*/
avg_local_sample_len = local_samples_len/NR_ACCUMULATED_SAMPLES;
if (avg_local_sample_len <= allowed_ns)
return;
if (max_samples_per_tick <= 1)
return;
max_samples_per_tick = DIV_ROUND_UP(max_samples_per_tick, 2);
sysctl_perf_event_sample_rate = max_samples_per_tick * HZ;
perf_sample_period_ns = NSEC_PER_SEC / sysctl_perf_event_sample_rate;
update_perf_cpu_limits();
if (!irq_work_queue(&perf_duration_work)) {
early_printk("perf interrupt took too long (%lld > %lld), lowering "
"kernel.perf_event_max_sample_rate to %d\n",
avg_local_sample_len, allowed_ns >> 1,
sysctl_perf_event_sample_rate);
}
}
static atomic64_t perf_event_id;
static void cpu_ctx_sched_out(struct perf_cpu_context *cpuctx,
enum event_type_t event_type);
static void cpu_ctx_sched_in(struct perf_cpu_context *cpuctx,
enum event_type_t event_type,
struct task_struct *task);
static void update_context_time(struct perf_event_context *ctx);
static u64 perf_event_time(struct perf_event *event);
void __weak perf_event_print_debug(void) { }
extern __weak const char *perf_pmu_name(void)
{
return "pmu";
}
static inline u64 perf_clock(void)
{
return local_clock();
}
static inline struct perf_cpu_context *
__get_cpu_context(struct perf_event_context *ctx)
{
return this_cpu_ptr(ctx->pmu->pmu_cpu_context);
}
static void perf_ctx_lock(struct perf_cpu_context *cpuctx,
struct perf_event_context *ctx)
{
raw_spin_lock(&cpuctx->ctx.lock);
if (ctx)
raw_spin_lock(&ctx->lock);
}
static void perf_ctx_unlock(struct perf_cpu_context *cpuctx,
struct perf_event_context *ctx)
{
if (ctx)
raw_spin_unlock(&ctx->lock);
raw_spin_unlock(&cpuctx->ctx.lock);
}
#ifdef CONFIG_CGROUP_PERF
/*
* perf_cgroup_info keeps track of time_enabled for a cgroup.
* This is a per-cpu dynamically allocated data structure.
*/
struct perf_cgroup_info {
u64 time;
u64 timestamp;
};
struct perf_cgroup {
struct cgroup_subsys_state css;
struct perf_cgroup_info __percpu *info;
};
/*
* Must ensure cgroup is pinned (css_get) before calling
* this function. In other words, we cannot call this function
* if there is no cgroup event for the current CPU context.
*/
static inline struct perf_cgroup *
perf_cgroup_from_task(struct task_struct *task)
{
return container_of(task_css(task, perf_event_cgrp_id),
struct perf_cgroup, css);
}
static inline bool
perf_cgroup_match(struct perf_event *event)
{
struct perf_event_context *ctx = event->ctx;
struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
/* @event doesn't care about cgroup */
if (!event->cgrp)
return true;
/* wants specific cgroup scope but @cpuctx isn't associated with any */
if (!cpuctx->cgrp)
return false;
/*
* Cgroup scoping is recursive. An event enabled for a cgroup is
* also enabled for all its descendant cgroups. If @cpuctx's
* cgroup is a descendant of @event's (the test covers identity
* case), it's a match.
*/
return cgroup_is_descendant(cpuctx->cgrp->css.cgroup,
event->cgrp->css.cgroup);
}
static inline void perf_detach_cgroup(struct perf_event *event)
{
css_put(&event->cgrp->css);
event->cgrp = NULL;
}
static inline int is_cgroup_event(struct perf_event *event)
{
return event->cgrp != NULL;
}
static inline u64 perf_cgroup_event_time(struct perf_event *event)
{
struct perf_cgroup_info *t;
t = per_cpu_ptr(event->cgrp->info, event->cpu);
return t->time;
}
static inline void __update_cgrp_time(struct perf_cgroup *cgrp)
{
struct perf_cgroup_info *info;
u64 now;
now = perf_clock();
info = this_cpu_ptr(cgrp->info);
info->time += now - info->timestamp;
info->timestamp = now;
}
static inline void update_cgrp_time_from_cpuctx(struct perf_cpu_context *cpuctx)
{
struct perf_cgroup *cgrp_out = cpuctx->cgrp;
if (cgrp_out)
__update_cgrp_time(cgrp_out);
}
static inline void update_cgrp_time_from_event(struct perf_event *event)
{
struct perf_cgroup *cgrp;
/*
* ensure we access cgroup data only when needed and
* when we know the cgroup is pinned (css_get)
*/
if (!is_cgroup_event(event))
return;
cgrp = perf_cgroup_from_task(current);
/*
* Do not update time when cgroup is not active
*/
if (cgrp == event->cgrp)
__update_cgrp_time(event->cgrp);
}
static inline void
perf_cgroup_set_timestamp(struct task_struct *task,
struct perf_event_context *ctx)
{
struct perf_cgroup *cgrp;
struct perf_cgroup_info *info;
/*
* ctx->lock held by caller
* ensure we do not access cgroup data
* unless we have the cgroup pinned (css_get)
*/
if (!task || !ctx->nr_cgroups)
return;
cgrp = perf_cgroup_from_task(task);
info = this_cpu_ptr(cgrp->info);
info->timestamp = ctx->timestamp;
}
#define PERF_CGROUP_SWOUT 0x1 /* cgroup switch out every event */
#define PERF_CGROUP_SWIN 0x2 /* cgroup switch in events based on task */
/*
* reschedule events based on the cgroup constraint of task.
*
* mode SWOUT : schedule out everything
* mode SWIN : schedule in based on cgroup for next
*/
void perf_cgroup_switch(struct task_struct *task, int mode)
{
struct perf_cpu_context *cpuctx;
struct pmu *pmu;
unsigned long flags;
/*
* disable interrupts to avoid geting nr_cgroup
* changes via __perf_event_disable(). Also
* avoids preemption.
*/
local_irq_save(flags);
/*
* we reschedule only in the presence of cgroup
* constrained events.
*/
rcu_read_lock();
list_for_each_entry_rcu(pmu, &pmus, entry) {
cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
if (cpuctx->unique_pmu != pmu)
continue; /* ensure we process each cpuctx once */
/*
* perf_cgroup_events says at least one
* context on this CPU has cgroup events.
*
* ctx->nr_cgroups reports the number of cgroup
* events for a context.
*/
if (cpuctx->ctx.nr_cgroups > 0) {
perf_ctx_lock(cpuctx, cpuctx->task_ctx);
perf_pmu_disable(cpuctx->ctx.pmu);
if (mode & PERF_CGROUP_SWOUT) {
cpu_ctx_sched_out(cpuctx, EVENT_ALL);
/*
* must not be done before ctxswout due
* to event_filter_match() in event_sched_out()
*/
cpuctx->cgrp = NULL;
}
if (mode & PERF_CGROUP_SWIN) {
WARN_ON_ONCE(cpuctx->cgrp);
/*
* set cgrp before ctxsw in to allow
* event_filter_match() to not have to pass
* task around
*/
cpuctx->cgrp = perf_cgroup_from_task(task);
cpu_ctx_sched_in(cpuctx, EVENT_ALL, task);
}
perf_pmu_enable(cpuctx->ctx.pmu);
perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
}
}
rcu_read_unlock();
local_irq_restore(flags);
}
static inline void perf_cgroup_sched_out(struct task_struct *task,
struct task_struct *next)
{
struct perf_cgroup *cgrp1;
struct perf_cgroup *cgrp2 = NULL;
/*
* we come here when we know perf_cgroup_events > 0
*/
cgrp1 = perf_cgroup_from_task(task);
/*
* next is NULL when called from perf_event_enable_on_exec()
* that will systematically cause a cgroup_switch()
*/
if (next)
cgrp2 = perf_cgroup_from_task(next);
/*
* only schedule out current cgroup events if we know
* that we are switching to a different cgroup. Otherwise,
* do no touch the cgroup events.
*/
if (cgrp1 != cgrp2)
perf_cgroup_switch(task, PERF_CGROUP_SWOUT);
}
static inline void perf_cgroup_sched_in(struct task_struct *prev,
struct task_struct *task)
{
struct perf_cgroup *cgrp1;
struct perf_cgroup *cgrp2 = NULL;
/*
* we come here when we know perf_cgroup_events > 0
*/
cgrp1 = perf_cgroup_from_task(task);
/* prev can never be NULL */
cgrp2 = perf_cgroup_from_task(prev);
/*
* only need to schedule in cgroup events if we are changing
* cgroup during ctxsw. Cgroup events were not scheduled
* out of ctxsw out if that was not the case.
*/
if (cgrp1 != cgrp2)
perf_cgroup_switch(task, PERF_CGROUP_SWIN);
}
static inline int perf_cgroup_connect(int fd, struct perf_event *event,
struct perf_event_attr *attr,
struct perf_event *group_leader)
{
struct perf_cgroup *cgrp;
struct cgroup_subsys_state *css;
struct fd f = fdget(fd);
int ret = 0;
if (!f.file)
return -EBADF;
css = css_tryget_online_from_dir(f.file->f_path.dentry,
&perf_event_cgrp_subsys);
if (IS_ERR(css)) {
ret = PTR_ERR(css);
goto out;
}
cgrp = container_of(css, struct perf_cgroup, css);
event->cgrp = cgrp;
/*
* all events in a group must monitor
* the same cgroup because a task belongs
* to only one perf cgroup at a time
*/
if (group_leader && group_leader->cgrp != cgrp) {
perf_detach_cgroup(event);
ret = -EINVAL;
}
out:
fdput(f);
return ret;
}
static inline void
perf_cgroup_set_shadow_time(struct perf_event *event, u64 now)
{
struct perf_cgroup_info *t;
t = per_cpu_ptr(event->cgrp->info, event->cpu);
event->shadow_ctx_time = now - t->timestamp;
}
static inline void
perf_cgroup_defer_enabled(struct perf_event *event)
{
/*
* when the current task's perf cgroup does not match
* the event's, we need to remember to call the
* perf_mark_enable() function the first time a task with
* a matching perf cgroup is scheduled in.
*/
if (is_cgroup_event(event) && !perf_cgroup_match(event))
event->cgrp_defer_enabled = 1;
}
static inline void
perf_cgroup_mark_enabled(struct perf_event *event,
struct perf_event_context *ctx)
{
struct perf_event *sub;
u64 tstamp = perf_event_time(event);
if (!event->cgrp_defer_enabled)
return;
event->cgrp_defer_enabled = 0;
event->tstamp_enabled = tstamp - event->total_time_enabled;
list_for_each_entry(sub, &event->sibling_list, group_entry) {
if (sub->state >= PERF_EVENT_STATE_INACTIVE) {
sub->tstamp_enabled = tstamp - sub->total_time_enabled;
sub->cgrp_defer_enabled = 0;
}
}
}
#else /* !CONFIG_CGROUP_PERF */
static inline bool
perf_cgroup_match(struct perf_event *event)
{
return true;
}
static inline void perf_detach_cgroup(struct perf_event *event)
{}
static inline int is_cgroup_event(struct perf_event *event)
{
return 0;
}
static inline u64 perf_cgroup_event_cgrp_time(struct perf_event *event)
{
return 0;
}
static inline void update_cgrp_time_from_event(struct perf_event *event)
{
}
static inline void update_cgrp_time_from_cpuctx(struct perf_cpu_context *cpuctx)
{
}
static inline void perf_cgroup_sched_out(struct task_struct *task,
struct task_struct *next)
{
}
static inline void perf_cgroup_sched_in(struct task_struct *prev,
struct task_struct *task)
{
}
static inline int perf_cgroup_connect(pid_t pid, struct perf_event *event,
struct perf_event_attr *attr,
struct perf_event *group_leader)
{
return -EINVAL;
}
static inline void
perf_cgroup_set_timestamp(struct task_struct *task,
struct perf_event_context *ctx)
{
}
void
perf_cgroup_switch(struct task_struct *task, struct task_struct *next)
{
}
static inline void
perf_cgroup_set_shadow_time(struct perf_event *event, u64 now)
{
}
static inline u64 perf_cgroup_event_time(struct perf_event *event)
{
return 0;
}
static inline void
perf_cgroup_defer_enabled(struct perf_event *event)
{
}
static inline void
perf_cgroup_mark_enabled(struct perf_event *event,
struct perf_event_context *ctx)
{
}
#endif
/*
* set default to be dependent on timer tick just
* like original code
*/
#define PERF_CPU_HRTIMER (1000 / HZ)
/*
* function must be called with interrupts disbled
*/
static enum hrtimer_restart perf_cpu_hrtimer_handler(struct hrtimer *hr)
{
struct perf_cpu_context *cpuctx;
enum hrtimer_restart ret = HRTIMER_NORESTART;
int rotations = 0;
WARN_ON(!irqs_disabled());
cpuctx = container_of(hr, struct perf_cpu_context, hrtimer);
rotations = perf_rotate_context(cpuctx);
/*
* arm timer if needed
*/
if (rotations) {
hrtimer_forward_now(hr, cpuctx->hrtimer_interval);
ret = HRTIMER_RESTART;
}
return ret;
}
/* CPU is going down */
void perf_cpu_hrtimer_cancel(int cpu)
{
struct perf_cpu_context *cpuctx;
struct pmu *pmu;
unsigned long flags;
if (WARN_ON(cpu != smp_processor_id()))
return;
local_irq_save(flags);
rcu_read_lock();
list_for_each_entry_rcu(pmu, &pmus, entry) {
cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
if (pmu->task_ctx_nr == perf_sw_context)
continue;
hrtimer_cancel(&cpuctx->hrtimer);
}
rcu_read_unlock();
local_irq_restore(flags);
}
static void __perf_cpu_hrtimer_init(struct perf_cpu_context *cpuctx, int cpu)
{
struct hrtimer *hr = &cpuctx->hrtimer;
struct pmu *pmu = cpuctx->ctx.pmu;
int timer;
/* no multiplexing needed for SW PMU */
if (pmu->task_ctx_nr == perf_sw_context)
return;
/*
* check default is sane, if not set then force to
* default interval (1/tick)
*/
timer = pmu->hrtimer_interval_ms;
if (timer < 1)
timer = pmu->hrtimer_interval_ms = PERF_CPU_HRTIMER;
cpuctx->hrtimer_interval = ns_to_ktime(NSEC_PER_MSEC * timer);
hrtimer_init(hr, CLOCK_MONOTONIC, HRTIMER_MODE_REL_PINNED);
hr->function = perf_cpu_hrtimer_handler;
}
static void perf_cpu_hrtimer_restart(struct perf_cpu_context *cpuctx)
{
struct hrtimer *hr = &cpuctx->hrtimer;
struct pmu *pmu = cpuctx->ctx.pmu;
/* not for SW PMU */
if (pmu->task_ctx_nr == perf_sw_context)
return;
if (hrtimer_active(hr))
return;
if (!hrtimer_callback_running(hr))
__hrtimer_start_range_ns(hr, cpuctx->hrtimer_interval,
0, HRTIMER_MODE_REL_PINNED, 0);
}
void perf_pmu_disable(struct pmu *pmu)
{
int *count = this_cpu_ptr(pmu->pmu_disable_count);
if (!(*count)++)
pmu->pmu_disable(pmu);
}
void perf_pmu_enable(struct pmu *pmu)
{
int *count = this_cpu_ptr(pmu->pmu_disable_count);
if (!--(*count))
pmu->pmu_enable(pmu);
}
static DEFINE_PER_CPU(struct list_head, active_ctx_list);
/*
* perf_event_ctx_activate(), perf_event_ctx_deactivate(), and
* perf_event_task_tick() are fully serialized because they're strictly cpu
* affine and perf_event_ctx{activate,deactivate} are called with IRQs
* disabled, while perf_event_task_tick is called from IRQ context.
*/
static void perf_event_ctx_activate(struct perf_event_context *ctx)
{
struct list_head *head = this_cpu_ptr(&active_ctx_list);
WARN_ON(!irqs_disabled());
WARN_ON(!list_empty(&ctx->active_ctx_list));
list_add(&ctx->active_ctx_list, head);
}
static void perf_event_ctx_deactivate(struct perf_event_context *ctx)
{
WARN_ON(!irqs_disabled());
WARN_ON(list_empty(&ctx->active_ctx_list));
list_del_init(&ctx->active_ctx_list);
}
static void get_ctx(struct perf_event_context *ctx)
{
WARN_ON(!atomic_inc_not_zero(&ctx->refcount));
}
static void put_ctx(struct perf_event_context *ctx)
{
if (atomic_dec_and_test(&ctx->refcount)) {
if (ctx->parent_ctx)
put_ctx(ctx->parent_ctx);
if (ctx->task)
put_task_struct(ctx->task);
kfree_rcu(ctx, rcu_head);
}
}
/*
* Because of perf_event::ctx migration in sys_perf_event_open::move_group and
* perf_pmu_migrate_context() we need some magic.
*
* Those places that change perf_event::ctx will hold both
* perf_event_ctx::mutex of the 'old' and 'new' ctx value.
*
* Lock ordering is by mutex address. There is one other site where
* perf_event_context::mutex nests and that is put_event(). But remember that
* that is a parent<->child context relation, and migration does not affect
* children, therefore these two orderings should not interact.
*
* The change in perf_event::ctx does not affect children (as claimed above)
* because the sys_perf_event_open() case will install a new event and break
* the ctx parent<->child relation, and perf_pmu_migrate_context() is only
* concerned with cpuctx and that doesn't have children.
*
* The places that change perf_event::ctx will issue:
*
* perf_remove_from_context();
* synchronize_rcu();
* perf_install_in_context();
*
* to affect the change. The remove_from_context() + synchronize_rcu() should
* quiesce the event, after which we can install it in the new location. This
* means that only external vectors (perf_fops, prctl) can perturb the event
* while in transit. Therefore all such accessors should also acquire
* perf_event_context::mutex to serialize against this.
*
* However; because event->ctx can change while we're waiting to acquire
* ctx->mutex we must be careful and use the below perf_event_ctx_lock()
* function.
*
* Lock order:
* task_struct::perf_event_mutex
* perf_event_context::mutex
* perf_event_context::lock
* perf_event::child_mutex;
* perf_event::mmap_mutex
* mmap_sem
*/
static struct perf_event_context *
perf_event_ctx_lock_nested(struct perf_event *event, int nesting)
{
struct perf_event_context *ctx;
again:
rcu_read_lock();
ctx = ACCESS_ONCE(event->ctx);
if (!atomic_inc_not_zero(&ctx->refcount)) {
rcu_read_unlock();
goto again;
}
rcu_read_unlock();
mutex_lock_nested(&ctx->mutex, nesting);
if (event->ctx != ctx) {
mutex_unlock(&ctx->mutex);
put_ctx(ctx);
goto again;
}
return ctx;
}
static inline struct perf_event_context *
perf_event_ctx_lock(struct perf_event *event)
{
return perf_event_ctx_lock_nested(event, 0);
}
static void perf_event_ctx_unlock(struct perf_event *event,
struct perf_event_context *ctx)
{
mutex_unlock(&ctx->mutex);
put_ctx(ctx);
}
/*
* This must be done under the ctx->lock, such as to serialize against
* context_equiv(), therefore we cannot call put_ctx() since that might end up
* calling scheduler related locks and ctx->lock nests inside those.
*/
static __must_check struct perf_event_context *
unclone_ctx(struct perf_event_context *ctx)
{
struct perf_event_context *parent_ctx = ctx->parent_ctx;
lockdep_assert_held(&ctx->lock);
if (parent_ctx)
ctx->parent_ctx = NULL;
ctx->generation++;
return parent_ctx;
}
static u32 perf_event_pid(struct perf_event *event, struct task_struct *p)
{
/*
* only top level events have the pid namespace they were created in
*/
if (event->parent)
event = event->parent;
return task_tgid_nr_ns(p, event->ns);
}
static u32 perf_event_tid(struct perf_event *event, struct task_struct *p)
{
/*
* only top level events have the pid namespace they were created in
*/
if (event->parent)
event = event->parent;
return task_pid_nr_ns(p, event->ns);
}
/*
* If we inherit events we want to return the parent event id
* to userspace.
*/
static u64 primary_event_id(struct perf_event *event)
{
u64 id = event->id;
if (event->parent)
id = event->parent->id;
return id;
}
/*
* Get the perf_event_context for a task and lock it.
* This has to cope with with the fact that until it is locked,
* the context could get moved to another task.
*/
static struct perf_event_context *
perf_lock_task_context(struct task_struct *task, int ctxn, unsigned long *flags)
{
struct perf_event_context *ctx;
retry:
/*
* One of the few rules of preemptible RCU is that one cannot do
* rcu_read_unlock() while holding a scheduler (or nested) lock when
* part of the read side critical section was preemptible -- see
* rcu_read_unlock_special().
*
* Since ctx->lock nests under rq->lock we must ensure the entire read
* side critical section is non-preemptible.
*/
preempt_disable();
rcu_read_lock();
ctx = rcu_dereference(task->perf_event_ctxp[ctxn]);
if (ctx) {
/*
* If this context is a clone of another, it might
* get swapped for another underneath us by
* perf_event_task_sched_out, though the
* rcu_read_lock() protects us from any context
* getting freed. Lock the context and check if it
* got swapped before we could get the lock, and retry
* if so. If we locked the right context, then it
* can't get swapped on us any more.
*/
raw_spin_lock_irqsave(&ctx->lock, *flags);
if (ctx != rcu_dereference(task->perf_event_ctxp[ctxn])) {
raw_spin_unlock_irqrestore(&ctx->lock, *flags);
rcu_read_unlock();
preempt_enable();
goto retry;
}
if (!atomic_inc_not_zero(&ctx->refcount)) {
raw_spin_unlock_irqrestore(&ctx->lock, *flags);
ctx = NULL;
}
}
rcu_read_unlock();
preempt_enable();
return ctx;
}
/*
* Get the context for a task and increment its pin_count so it
* can't get swapped to another task. This also increments its
* reference count so that the context can't get freed.
*/
static struct perf_event_context *
perf_pin_task_context(struct task_struct *task, int ctxn)
{
struct perf_event_context *ctx;
unsigned long flags;
ctx = perf_lock_task_context(task, ctxn, &flags);
if (ctx) {
++ctx->pin_count;
raw_spin_unlock_irqrestore(&ctx->lock, flags);
}
return ctx;
}
static void perf_unpin_context(struct perf_event_context *ctx)
{
unsigned long flags;
raw_spin_lock_irqsave(&ctx->lock, flags);
--ctx->pin_count;
raw_spin_unlock_irqrestore(&ctx->lock, flags);
}
/*
* Update the record of the current time in a context.
*/
static void update_context_time(struct perf_event_context *ctx)
{
u64 now = perf_clock();
ctx->time += now - ctx->timestamp;
ctx->timestamp = now;
}
static u64 perf_event_time(struct perf_event *event)
{
struct perf_event_context *ctx = event->ctx;
if (is_cgroup_event(event))
return perf_cgroup_event_time(event);
return ctx ? ctx->time : 0;
}
/*
* Update the total_time_enabled and total_time_running fields for a event.
* The caller of this function needs to hold the ctx->lock.
*/
static void update_event_times(struct perf_event *event)
{
struct perf_event_context *ctx = event->ctx;
u64 run_end;
if (event->state < PERF_EVENT_STATE_INACTIVE ||
event->group_leader->state < PERF_EVENT_STATE_INACTIVE)
return;
/*
* in cgroup mode, time_enabled represents
* the time the event was enabled AND active
* tasks were in the monitored cgroup. This is
* independent of the activity of the context as
* there may be a mix of cgroup and non-cgroup events.
*
* That is why we treat cgroup events differently
* here.
*/
if (is_cgroup_event(event))
run_end = perf_cgroup_event_time(event);
else if (ctx->is_active)
run_end = ctx->time;
else
run_end = event->tstamp_stopped;
event->total_time_enabled = run_end - event->tstamp_enabled;
if (event->state == PERF_EVENT_STATE_INACTIVE)
run_end = event->tstamp_stopped;
else
run_end = perf_event_time(event);
event->total_time_running = run_end - event->tstamp_running;
}
/*
* Update total_time_enabled and total_time_running for all events in a group.
*/
static void update_group_times(struct perf_event *leader)
{
struct perf_event *event;
update_event_times(leader);
list_for_each_entry(event, &leader->sibling_list, group_entry)
update_event_times(event);
}
static struct list_head *
ctx_group_list(struct perf_event *event, struct perf_event_context *ctx)
{
if (event->attr.pinned)
return &ctx->pinned_groups;
else
return &ctx->flexible_groups;
}
/*
* Add a event from the lists for its context.
* Must be called with ctx->mutex and ctx->lock held.
*/
static void
list_add_event(struct perf_event *event, struct perf_event_context *ctx)
{
WARN_ON_ONCE(event->attach_state & PERF_ATTACH_CONTEXT);
event->attach_state |= PERF_ATTACH_CONTEXT;
/*
* If we're a stand alone event or group leader, we go to the context
* list, group events are kept attached to the group so that
* perf_group_detach can, at all times, locate all siblings.
*/
if (event->group_leader == event) {
struct list_head *list;
if (is_software_event(event))
event->group_flags |= PERF_GROUP_SOFTWARE;
list = ctx_group_list(event, ctx);
list_add_tail(&event->group_entry, list);
}
if (is_cgroup_event(event))
ctx->nr_cgroups++;
if (has_branch_stack(event))
ctx->nr_branch_stack++;
list_add_rcu(&event->event_entry, &ctx->event_list);
ctx->nr_events++;
if (event->attr.inherit_stat)
ctx->nr_stat++;
ctx->generation++;
}
/*
* Initialize event state based on the perf_event_attr::disabled.
*/
static inline void perf_event__state_init(struct perf_event *event)
{
event->state = event->attr.disabled ? PERF_EVENT_STATE_OFF :
PERF_EVENT_STATE_INACTIVE;
}
/*
* Called at perf_event creation and when events are attached/detached from a
* group.
*/
static void perf_event__read_size(struct perf_event *event)
{
int entry = sizeof(u64); /* value */
int size = 0;
int nr = 1;
if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
size += sizeof(u64);
if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
size += sizeof(u64);
if (event->attr.read_format & PERF_FORMAT_ID)
entry += sizeof(u64);
if (event->attr.read_format & PERF_FORMAT_GROUP) {
nr += event->group_leader->nr_siblings;
size += sizeof(u64);
}
size += entry * nr;
event->read_size = size;
}
static void perf_event__header_size(struct perf_event *event)
{
struct perf_sample_data *data;
u64 sample_type = event->attr.sample_type;
u16 size = 0;
perf_event__read_size(event);
if (sample_type & PERF_SAMPLE_IP)
size += sizeof(data->ip);
if (sample_type & PERF_SAMPLE_ADDR)
size += sizeof(data->addr);
if (sample_type & PERF_SAMPLE_PERIOD)
size += sizeof(data->period);
if (sample_type & PERF_SAMPLE_WEIGHT)
size += sizeof(data->weight);
if (sample_type & PERF_SAMPLE_READ)
size += event->read_size;
if (sample_type & PERF_SAMPLE_DATA_SRC)
size += sizeof(data->data_src.val);
if (sample_type & PERF_SAMPLE_TRANSACTION)
size += sizeof(data->txn);
event->header_size = size;
}
static void perf_event__id_header_size(struct perf_event *event)
{
struct perf_sample_data *data;
u64 sample_type = event->attr.sample_type;
u16 size = 0;
if (sample_type & PERF_SAMPLE_TID)
size += sizeof(data->tid_entry);
if (sample_type & PERF_SAMPLE_TIME)
size += sizeof(data->time);
if (sample_type & PERF_SAMPLE_IDENTIFIER)
size += sizeof(data->id);
if (sample_type & PERF_SAMPLE_ID)
size += sizeof(data->id);
if (sample_type & PERF_SAMPLE_STREAM_ID)
size += sizeof(data->stream_id);
if (sample_type & PERF_SAMPLE_CPU)
size += sizeof(data->cpu_entry);
event->id_header_size = size;
}
static void perf_group_attach(struct perf_event *event)
{
struct perf_event *group_leader = event->group_leader, *pos;
/*
* We can have double attach due to group movement in perf_event_open.
*/
if (event->attach_state & PERF_ATTACH_GROUP)
return;
event->attach_state |= PERF_ATTACH_GROUP;
if (group_leader == event)
return;
WARN_ON_ONCE(group_leader->ctx != event->ctx);
if (group_leader->group_flags & PERF_GROUP_SOFTWARE &&
!is_software_event(event))
group_leader->group_flags &= ~PERF_GROUP_SOFTWARE;
list_add_tail(&event->group_entry, &group_leader->sibling_list);
group_leader->nr_siblings++;
perf_event__header_size(group_leader);
list_for_each_entry(pos, &group_leader->sibling_list, group_entry)
perf_event__header_size(pos);
}
/*
* Remove a event from the lists for its context.
* Must be called with ctx->mutex and ctx->lock held.
*/
static void
list_del_event(struct perf_event *event, struct perf_event_context *ctx)
{
struct perf_cpu_context *cpuctx;
WARN_ON_ONCE(event->ctx != ctx);
lockdep_assert_held(&ctx->lock);
/*
* We can have double detach due to exit/hot-unplug + close.
*/
if (!(event->attach_state & PERF_ATTACH_CONTEXT))
return;
event->attach_state &= ~PERF_ATTACH_CONTEXT;
if (is_cgroup_event(event)) {
ctx->nr_cgroups--;
cpuctx = __get_cpu_context(ctx);
/*
* if there are no more cgroup events
* then cler cgrp to avoid stale pointer
* in update_cgrp_time_from_cpuctx()
*/
if (!ctx->nr_cgroups)
cpuctx->cgrp = NULL;
}
if (has_branch_stack(event))
ctx->nr_branch_stack--;
ctx->nr_events--;
if (event->attr.inherit_stat)
ctx->nr_stat--;
list_del_rcu(&event->event_entry);
if (event->group_leader == event)
list_del_init(&event->group_entry);
update_group_times(event);
/*
* If event was in error state, then keep it
* that way, otherwise bogus counts will be
* returned on read(). The only way to get out
* of error state is by explicit re-enabling
* of the event
*/
if (event->state > PERF_EVENT_STATE_OFF)
event->state = PERF_EVENT_STATE_OFF;
ctx->generation++;
}
static void perf_group_detach(struct perf_event *event)
{
struct perf_event *sibling, *tmp;
struct list_head *list = NULL;
/*
* We can have double detach due to exit/hot-unplug + close.
*/
if (!(event->attach_state & PERF_ATTACH_GROUP))
return;
event->attach_state &= ~PERF_ATTACH_GROUP;
/*
* If this is a sibling, remove it from its group.
*/
if (event->group_leader != event) {
list_del_init(&event->group_entry);
event->group_leader->nr_siblings--;
goto out;
}
if (!list_empty(&event->group_entry))
list = &event->group_entry;
/*
* If this was a group event with sibling events then
* upgrade the siblings to singleton events by adding them
* to whatever list we are on.
*/
list_for_each_entry_safe(sibling, tmp, &event->sibling_list, group_entry) {
if (list)
list_move_tail(&sibling->group_entry, list);
sibling->group_leader = sibling;
/* Inherit group flags from the previous leader */
sibling->group_flags = event->group_flags;
WARN_ON_ONCE(sibling->ctx != event->ctx);
}
out:
perf_event__header_size(event->group_leader);
list_for_each_entry(tmp, &event->group_leader->sibling_list, group_entry)
perf_event__header_size(tmp);
}
/*
* User event without the task.
*/
static bool is_orphaned_event(struct perf_event *event)
{
return event && !is_kernel_event(event) && !event->owner;
}
/*
* Event has a parent but parent's task finished and it's
* alive only because of children holding refference.
*/
static bool is_orphaned_child(struct perf_event *event)
{
return is_orphaned_event(event->parent);
}
static void orphans_remove_work(struct work_struct *work);
static void schedule_orphans_remove(struct perf_event_context *ctx)
{
if (!ctx->task || ctx->orphans_remove_sched || !perf_wq)
return;
if (queue_delayed_work(perf_wq, &ctx->orphans_remove, 1)) {
get_ctx(ctx);
ctx->orphans_remove_sched = true;
}
}
static int __init perf_workqueue_init(void)
{
perf_wq = create_singlethread_workqueue("perf");
WARN(!perf_wq, "failed to create perf workqueue\n");
return perf_wq ? 0 : -1;
}
core_initcall(perf_workqueue_init);
static inline int
event_filter_match(struct perf_event *event)
{
return (event->cpu == -1 || event->cpu == smp_processor_id())
&& perf_cgroup_match(event);
}
static void
event_sched_out(struct perf_event *event,
struct perf_cpu_context *cpuctx,
struct perf_event_context *ctx)
{
u64 tstamp = perf_event_time(event);
u64 delta;
WARN_ON_ONCE(event->ctx != ctx);
lockdep_assert_held(&ctx->lock);
/*
* An event which could not be activated because of
* filter mismatch still needs to have its timings
* maintained, otherwise bogus information is return
* via read() for time_enabled, time_running:
*/
if (event->state == PERF_EVENT_STATE_INACTIVE
&& !event_filter_match(event)) {
delta = tstamp - event->tstamp_stopped;
event->tstamp_running += delta;
event->tstamp_stopped = tstamp;
}
if (event->state != PERF_EVENT_STATE_ACTIVE)
return;
perf_pmu_disable(event->pmu);
event->state = PERF_EVENT_STATE_INACTIVE;
if (event->pending_disable) {
event->pending_disable = 0;
event->state = PERF_EVENT_STATE_OFF;
}
event->tstamp_stopped = tstamp;
event->pmu->del(event, 0);
event->oncpu = -1;
if (!is_software_event(event))
cpuctx->active_oncpu--;
if (!--ctx->nr_active)
perf_event_ctx_deactivate(ctx);
if (event->attr.freq && event->attr.sample_freq)
ctx->nr_freq--;
if (event->attr.exclusive || !cpuctx->active_oncpu)
cpuctx->exclusive = 0;
if (is_orphaned_child(event))
schedule_orphans_remove(ctx);
perf_pmu_enable(event->pmu);
}
static void
group_sched_out(struct perf_event *group_event,
struct perf_cpu_context *cpuctx,
struct perf_event_context *ctx)
{
struct perf_event *event;
int state = group_event->state;
event_sched_out(group_event, cpuctx, ctx);
/*
* Schedule out siblings (if any):
*/
list_for_each_entry(event, &group_event->sibling_list, group_entry)
event_sched_out(event, cpuctx, ctx);
if (state == PERF_EVENT_STATE_ACTIVE && group_event->attr.exclusive)
cpuctx->exclusive = 0;
}
struct remove_event {
struct perf_event *event;
bool detach_group;
};
/*
* Cross CPU call to remove a performance event
*
* We disable the event on the hardware level first. After that we
* remove it from the context list.
*/
static int __perf_remove_from_context(void *info)
{
struct remove_event *re = info;
struct perf_event *event = re->event;
struct perf_event_context *ctx = event->ctx;
struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
raw_spin_lock(&ctx->lock);
event_sched_out(event, cpuctx, ctx);
if (re->detach_group)
perf_group_detach(event);
list_del_event(event, ctx);
if (!ctx->nr_events && cpuctx->task_ctx == ctx) {
ctx->is_active = 0;
cpuctx->task_ctx = NULL;
}
raw_spin_unlock(&ctx->lock);
return 0;
}
/*
* Remove the event from a task's (or a CPU's) list of events.
*
* CPU events are removed with a smp call. For task events we only
* call when the task is on a CPU.
*
* If event->ctx is a cloned context, callers must make sure that
* every task struct that event->ctx->task could possibly point to
* remains valid. This is OK when called from perf_release since
* that only calls us on the top-level context, which can't be a clone.
* When called from perf_event_exit_task, it's OK because the
* context has been detached from its task.
*/
static void perf_remove_from_context(struct perf_event *event, bool detach_group)
{
struct perf_event_context *ctx = event->ctx;
struct task_struct *task = ctx->task;
struct remove_event re = {
.event = event,
.detach_group = detach_group,
};
lockdep_assert_held(&ctx->mutex);
if (!task) {
/*
* Per cpu events are removed via an smp call. The removal can
* fail if the CPU is currently offline, but in that case we
* already called __perf_remove_from_context from
* perf_event_exit_cpu.
*/
cpu_function_call(event->cpu, __perf_remove_from_context, &re);
return;
}
retry:
if (!task_function_call(task, __perf_remove_from_context, &re))
return;
raw_spin_lock_irq(&ctx->lock);
/*
* If we failed to find a running task, but find the context active now
* that we've acquired the ctx->lock, retry.
*/
if (ctx->is_active) {
raw_spin_unlock_irq(&ctx->lock);
/*
* Reload the task pointer, it might have been changed by
* a concurrent perf_event_context_sched_out().
*/
task = ctx->task;
goto retry;
}
/*
* Since the task isn't running, its safe to remove the event, us
* holding the ctx->lock ensures the task won't get scheduled in.
*/
if (detach_group)
perf_group_detach(event);
list_del_event(event, ctx);
raw_spin_unlock_irq(&ctx->lock);
}
/*
* Cross CPU call to disable a performance event
*/
int __perf_event_disable(void *info)
{
struct perf_event *event = info;
struct perf_event_context *ctx = event->ctx;
struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
/*
* If this is a per-task event, need to check whether this
* event's task is the current task on this cpu.
*
* Can trigger due to concurrent perf_event_context_sched_out()
* flipping contexts around.
*/
if (ctx->task && cpuctx->task_ctx != ctx)
return -EINVAL;
raw_spin_lock(&ctx->lock);
/*
* If the event is on, turn it off.
* If it is in error state, leave it in error state.
*/
if (event->state >= PERF_EVENT_STATE_INACTIVE) {
update_context_time(ctx);
update_cgrp_time_from_event(event);
update_group_times(event);
if (event == event->group_leader)
group_sched_out(event, cpuctx, ctx);
else
event_sched_out(event, cpuctx, ctx);
event->state = PERF_EVENT_STATE_OFF;
}
raw_spin_unlock(&ctx->lock);
return 0;
}
/*
* Disable a event.
*
* If event->ctx is a cloned context, callers must make sure that
* every task struct that event->ctx->task could possibly point to
* remains valid. This condition is satisifed when called through
* perf_event_for_each_child or perf_event_for_each because they
* hold the top-level event's child_mutex, so any descendant that
* goes to exit will block in sync_child_event.
* When called from perf_pending_event it's OK because event->ctx
* is the current context on this CPU and preemption is disabled,
* hence we can't get into perf_event_task_sched_out for this context.
*/
static void _perf_event_disable(struct perf_event *event)
{
struct perf_event_context *ctx = event->ctx;
struct task_struct *task = ctx->task;
if (!task) {
/*
* Disable the event on the cpu that it's on
*/
cpu_function_call(event->cpu, __perf_event_disable, event);
return;
}
retry:
if (!task_function_call(task, __perf_event_disable, event))
return;
raw_spin_lock_irq(&ctx->lock);
/*
* If the event is still active, we need to retry the cross-call.
*/
if (event->state == PERF_EVENT_STATE_ACTIVE) {
raw_spin_unlock_irq(&ctx->lock);
/*
* Reload the task pointer, it might have been changed by
* a concurrent perf_event_context_sched_out().
*/
task = ctx->task;
goto retry;
}
/*
* Since we have the lock this context can't be scheduled
* in, so we can change the state safely.
*/
if (event->state == PERF_EVENT_STATE_INACTIVE) {
update_group_times(event);
event->state = PERF_EVENT_STATE_OFF;
}
raw_spin_unlock_irq(&ctx->lock);
}
/*
* Strictly speaking kernel users cannot create groups and therefore this
* interface does not need the perf_event_ctx_lock() magic.
*/
void perf_event_disable(struct perf_event *event)
{
struct perf_event_context *ctx;
ctx = perf_event_ctx_lock(event);
_perf_event_disable(event);
perf_event_ctx_unlock(event, ctx);
}
EXPORT_SYMBOL_GPL(perf_event_disable);
static void perf_set_shadow_time(struct perf_event *event,
struct perf_event_context *ctx,
u64 tstamp)
{
/*
* use the correct time source for the time snapshot
*
* We could get by without this by leveraging the
* fact that to get to this function, the caller
* has most likely already called update_context_time()
* and update_cgrp_time_xx() and thus both timestamp
* are identical (or very close). Given that tstamp is,
* already adjusted for cgroup, we could say that:
* tstamp - ctx->timestamp
* is equivalent to
* tstamp - cgrp->timestamp.
*
* Then, in perf_output_read(), the calculation would
* work with no changes because:
* - event is guaranteed scheduled in
* - no scheduled out in between
* - thus the timestamp would be the same
*
* But this is a bit hairy.
*
* So instead, we have an explicit cgroup call to remain
* within the time time source all along. We believe it
* is cleaner and simpler to understand.
*/
if (is_cgroup_event(event))
perf_cgroup_set_shadow_time(event, tstamp);
else
event->shadow_ctx_time = tstamp - ctx->timestamp;
}
#define MAX_INTERRUPTS (~0ULL)
static void perf_log_throttle(struct perf_event *event, int enable);
static int
event_sched_in(struct perf_event *event,
struct perf_cpu_context *cpuctx,
struct perf_event_context *ctx)
{
u64 tstamp = perf_event_time(event);
int ret = 0;
lockdep_assert_held(&ctx->lock);
if (event->state <= PERF_EVENT_STATE_OFF)
return 0;
event->state = PERF_EVENT_STATE_ACTIVE;
event->oncpu = smp_processor_id();
/*
* Unthrottle events, since we scheduled we might have missed several
* ticks already, also for a heavily scheduling task there is little
* guarantee it'll get a tick in a timely manner.
*/
if (unlikely(event->hw.interrupts == MAX_INTERRUPTS)) {
perf_log_throttle(event, 1);
event->hw.interrupts = 0;
}
/*
* The new state must be visible before we turn it on in the hardware:
*/
smp_wmb();
perf_pmu_disable(event->pmu);
if (event->pmu->add(event, PERF_EF_START)) {
event->state = PERF_EVENT_STATE_INACTIVE;
event->oncpu = -1;
ret = -EAGAIN;
goto out;
}
event->tstamp_running += tstamp - event->tstamp_stopped;
perf_set_shadow_time(event, ctx, tstamp);
if (!is_software_event(event))
cpuctx->active_oncpu++;
if (!ctx->nr_active++)
perf_event_ctx_activate(ctx);
if (event->attr.freq && event->attr.sample_freq)
ctx->nr_freq++;
if (event->attr.exclusive)
cpuctx->exclusive = 1;
if (is_orphaned_child(event))
schedule_orphans_remove(ctx);
out:
perf_pmu_enable(event->pmu);
return ret;
}
static int
group_sched_in(struct perf_event *group_event,
struct perf_cpu_context *cpuctx,
struct perf_event_context *ctx)
{
struct perf_event *event, *partial_group = NULL;
struct pmu *pmu = ctx->pmu;
u64 now = ctx->time;
bool simulate = false;
if (group_event->state == PERF_EVENT_STATE_OFF)
return 0;
pmu->start_txn(pmu);
if (event_sched_in(group_event, cpuctx, ctx)) {
pmu->cancel_txn(pmu);
perf_cpu_hrtimer_restart(cpuctx);
return -EAGAIN;
}
/*
* Schedule in siblings as one group (if any):
*/
list_for_each_entry(event, &group_event->sibling_list, group_entry) {
if (event_sched_in(event, cpuctx, ctx)) {
partial_group = event;
goto group_error;
}
}
if (!pmu->commit_txn(pmu))
return 0;
group_error:
/*
* Groups can be scheduled in as one unit only, so undo any
* partial group before returning:
* The events up to the failed event are scheduled out normally,
* tstamp_stopped will be updated.
*
* The failed events and the remaining siblings need to have
* their timings updated as if they had gone thru event_sched_in()
* and event_sched_out(). This is required to get consistent timings
* across the group. This also takes care of the case where the group
* could never be scheduled by ensuring tstamp_stopped is set to mark
* the time the event was actually stopped, such that time delta
* calculation in update_event_times() is correct.
*/
list_for_each_entry(event, &group_event->sibling_list, group_entry) {
if (event == partial_group)
simulate = true;
if (simulate) {
event->tstamp_running += now - event->tstamp_stopped;
event->tstamp_stopped = now;
} else {
event_sched_out(event, cpuctx, ctx);
}
}
event_sched_out(group_event, cpuctx, ctx);
pmu->cancel_txn(pmu);
perf_cpu_hrtimer_restart(cpuctx);
return -EAGAIN;
}
/*
* Work out whether we can put this event group on the CPU now.
*/
static int group_can_go_on(struct perf_event *event,
struct perf_cpu_context *cpuctx,
int can_add_hw)
{
/*
* Groups consisting entirely of software events can always go on.
*/
if (event->group_flags & PERF_GROUP_SOFTWARE)
return 1;
/*
* If an exclusive group is already on, no other hardware
* events can go on.
*/
if (cpuctx->exclusive)
return 0;
/*
* If this group is exclusive and there are already
* events on the CPU, it can't go on.
*/
if (event->attr.exclusive && cpuctx->active_oncpu)
return 0;
/*
* Otherwise, try to add it if all previous groups were able
* to go on.
*/
return can_add_hw;
}
static void add_event_to_ctx(struct perf_event *event,
struct perf_event_context *ctx)
{
u64 tstamp = perf_event_time(event);
list_add_event(event, ctx);
perf_group_attach(event);
event->tstamp_enabled = tstamp;
event->tstamp_running = tstamp;
event->tstamp_stopped = tstamp;
}
static void task_ctx_sched_out(struct perf_event_context *ctx);
static void
ctx_sched_in(struct perf_event_context *ctx,
struct perf_cpu_context *cpuctx,
enum event_type_t event_type,
struct task_struct *task);
static void perf_event_sched_in(struct perf_cpu_context *cpuctx,
struct perf_event_context *ctx,
struct task_struct *task)
{
cpu_ctx_sched_in(cpuctx, EVENT_PINNED, task);
if (ctx)
ctx_sched_in(ctx, cpuctx, EVENT_PINNED, task);
cpu_ctx_sched_in(cpuctx, EVENT_FLEXIBLE, task);
if (ctx)
ctx_sched_in(ctx, cpuctx, EVENT_FLEXIBLE, task);
}
/*
* Cross CPU call to install and enable a performance event
*
* Must be called with ctx->mutex held
*/
static int __perf_install_in_context(void *info)
{
struct perf_event *event = info;
struct perf_event_context *ctx = event->ctx;
struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
struct perf_event_context *task_ctx = cpuctx->task_ctx;
struct task_struct *task = current;
perf_ctx_lock(cpuctx, task_ctx);
perf_pmu_disable(cpuctx->ctx.pmu);
/*
* If there was an active task_ctx schedule it out.
*/
if (task_ctx)
task_ctx_sched_out(task_ctx);
/*
* If the context we're installing events in is not the
* active task_ctx, flip them.
*/
if (ctx->task && task_ctx != ctx) {
if (task_ctx)
raw_spin_unlock(&task_ctx->lock);
raw_spin_lock(&ctx->lock);
task_ctx = ctx;
}
if (task_ctx) {
cpuctx->task_ctx = task_ctx;
task = task_ctx->task;
}
cpu_ctx_sched_out(cpuctx, EVENT_ALL);
update_context_time(ctx);
/*
* update cgrp time only if current cgrp
* matches event->cgrp. Must be done before
* calling add_event_to_ctx()
*/
update_cgrp_time_from_event(event);
add_event_to_ctx(event, ctx);
/*
* Schedule everything back in
*/
perf_event_sched_in(cpuctx, task_ctx, task);
perf_pmu_enable(cpuctx->ctx.pmu);
perf_ctx_unlock(cpuctx, task_ctx);
return 0;
}
/*
* Attach a performance event to a context
*
* First we add the event to the list with the hardware enable bit
* in event->hw_config cleared.
*
* If the event is attached to a task which is on a CPU we use a smp
* call to enable it in the task context. The task might have been
* scheduled away, but we check this in the smp call again.
*/
static void
perf_install_in_context(struct perf_event_context *ctx,
struct perf_event *event,
int cpu)
{
struct task_struct *task = ctx->task;
lockdep_assert_held(&ctx->mutex);
event->ctx = ctx;
if (event->cpu != -1)
event->cpu = cpu;
if (!task) {
/*
* Per cpu events are installed via an smp call and
* the install is always successful.
*/
cpu_function_call(cpu, __perf_install_in_context, event);
return;
}
retry:
if (!task_function_call(task, __perf_install_in_context, event))
return;
raw_spin_lock_irq(&ctx->lock);
/*
* If we failed to find a running task, but find the context active now
* that we've acquired the ctx->lock, retry.
*/
if (ctx->is_active) {
raw_spin_unlock_irq(&ctx->lock);
/*
* Reload the task pointer, it might have been changed by
* a concurrent perf_event_context_sched_out().
*/
task = ctx->task;
goto retry;
}
/*
* Since the task isn't running, its safe to add the event, us holding
* the ctx->lock ensures the task won't get scheduled in.
*/
add_event_to_ctx(event, ctx);
raw_spin_unlock_irq(&ctx->lock);
}
/*
* Put a event into inactive state and update time fields.
* Enabling the leader of a group effectively enables all
* the group members that aren't explicitly disabled, so we
* have to update their ->tstamp_enabled also.
* Note: this works for group members as well as group leaders
* since the non-leader members' sibling_lists will be empty.
*/
static void __perf_event_mark_enabled(struct perf_event *event)
{
struct perf_event *sub;
u64 tstamp = perf_event_time(event);
event->state = PERF_EVENT_STATE_INACTIVE;
event->tstamp_enabled = tstamp - event->total_time_enabled;
list_for_each_entry(sub, &event->sibling_list, group_entry) {
if (sub->state >= PERF_EVENT_STATE_INACTIVE)
sub->tstamp_enabled = tstamp - sub->total_time_enabled;
}
}
/*
* Cross CPU call to enable a performance event
*/
static int __perf_event_enable(void *info)
{
struct perf_event *event = info;
struct perf_event_context *ctx = event->ctx;
struct perf_event *leader = event->group_leader;
struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
int err;
/*
* There's a time window between 'ctx->is_active' check
* in perf_event_enable function and this place having:
* - IRQs on
* - ctx->lock unlocked
*
* where the task could be killed and 'ctx' deactivated
* by perf_event_exit_task.
*/
if (!ctx->is_active)
return -EINVAL;
raw_spin_lock(&ctx->lock);
update_context_time(ctx);
if (event->state >= PERF_EVENT_STATE_INACTIVE)
goto unlock;
/*
* set current task's cgroup time reference point
*/
perf_cgroup_set_timestamp(current, ctx);
__perf_event_mark_enabled(event);
if (!event_filter_match(event)) {
if (is_cgroup_event(event))
perf_cgroup_defer_enabled(event);
goto unlock;
}
/*
* If the event is in a group and isn't the group leader,
* then don't put it on unless the group is on.
*/
if (leader != event && leader->state != PERF_EVENT_STATE_ACTIVE)
goto unlock;
if (!group_can_go_on(event, cpuctx, 1)) {
err = -EEXIST;
} else {
if (event == leader)
err = group_sched_in(event, cpuctx, ctx);
else
err = event_sched_in(event, cpuctx, ctx);
}
if (err) {
/*
* If this event can't go on and it's part of a
* group, then the whole group has to come off.
*/
if (leader != event) {
group_sched_out(leader, cpuctx, ctx);
perf_cpu_hrtimer_restart(cpuctx);
}
if (leader->attr.pinned) {
update_group_times(leader);
leader->state = PERF_EVENT_STATE_ERROR;
}
}
unlock:
raw_spin_unlock(&ctx->lock);
return 0;
}
/*
* Enable a event.
*
* If event->ctx is a cloned context, callers must make sure that
* every task struct that event->ctx->task could possibly point to
* remains valid. This condition is satisfied when called through
* perf_event_for_each_child or perf_event_for_each as described
* for perf_event_disable.
*/
static void _perf_event_enable(struct perf_event *event)
{
struct perf_event_context *ctx = event->ctx;
struct task_struct *task = ctx->task;
if (!task) {
/*
* Enable the event on the cpu that it's on
*/
cpu_function_call(event->cpu, __perf_event_enable, event);
return;
}
raw_spin_lock_irq(&ctx->lock);
if (event->state >= PERF_EVENT_STATE_INACTIVE)
goto out;
/*
* If the event is in error state, clear that first.
* That way, if we see the event in error state below, we
* know that it has gone back into error state, as distinct
* from the task having been scheduled away before the
* cross-call arrived.
*/
if (event->state == PERF_EVENT_STATE_ERROR)
event->state = PERF_EVENT_STATE_OFF;
retry:
if (!ctx->is_active) {
__perf_event_mark_enabled(event);
goto out;
}
raw_spin_unlock_irq(&ctx->lock);
if (!task_function_call(task, __perf_event_enable, event))
return;
raw_spin_lock_irq(&ctx->lock);
/*
* If the context is active and the event is still off,
* we need to retry the cross-call.
*/
if (ctx->is_active && event->state == PERF_EVENT_STATE_OFF) {
/*
* task could have been flipped by a concurrent
* perf_event_context_sched_out()
*/
task = ctx->task;
goto retry;
}
out:
raw_spin_unlock_irq(&ctx->lock);
}
/*
* See perf_event_disable();
*/
void perf_event_enable(struct perf_event *event)
{
struct perf_event_context *ctx;
ctx = perf_event_ctx_lock(event);
_perf_event_enable(event);
perf_event_ctx_unlock(event, ctx);
}
EXPORT_SYMBOL_GPL(perf_event_enable);
static int _perf_event_refresh(struct perf_event *event, int refresh)
{
/*
* not supported on inherited events
*/
if (event->attr.inherit || !is_sampling_event(event))
return -EINVAL;
atomic_add(refresh, &event->event_limit);
_perf_event_enable(event);
return 0;
}
/*
* See perf_event_disable()
*/
int perf_event_refresh(struct perf_event *event, int refresh)
{
struct perf_event_context *ctx;
int ret;
ctx = perf_event_ctx_lock(event);
ret = _perf_event_refresh(event, refresh);
perf_event_ctx_unlock(event, ctx);
return ret;
}
EXPORT_SYMBOL_GPL(perf_event_refresh);
static void ctx_sched_out(struct perf_event_context *ctx,
struct perf_cpu_context *cpuctx,
enum event_type_t event_type)
{
struct perf_event *event;
int is_active = ctx->is_active;
ctx->is_active &= ~event_type;
if (likely(!ctx->nr_events))
return;
update_context_time(ctx);
update_cgrp_time_from_cpuctx(cpuctx);
if (!ctx->nr_active)
return;
perf_pmu_disable(ctx->pmu);
if ((is_active & EVENT_PINNED) && (event_type & EVENT_PINNED)) {
list_for_each_entry(event, &ctx->pinned_groups, group_entry)
group_sched_out(event, cpuctx, ctx);
}
if ((is_active & EVENT_FLEXIBLE) && (event_type & EVENT_FLEXIBLE)) {
list_for_each_entry(event, &ctx->flexible_groups, group_entry)
group_sched_out(event, cpuctx, ctx);
}
perf_pmu_enable(ctx->pmu);
}
/*
* Test whether two contexts are equivalent, i.e. whether they have both been
* cloned from the same version of the same context.
*
* Equivalence is measured using a generation number in the context that is
* incremented on each modification to it; see unclone_ctx(), list_add_event()
* and list_del_event().
*/
static int context_equiv(struct perf_event_context *ctx1,
struct perf_event_context *ctx2)
{
lockdep_assert_held(&ctx1->lock);
lockdep_assert_held(&ctx2->lock);
/* Pinning disables the swap optimization */
if (ctx1->pin_count || ctx2->pin_count)
return 0;
/* If ctx1 is the parent of ctx2 */
if (ctx1 == ctx2->parent_ctx && ctx1->generation == ctx2->parent_gen)
return 1;
/* If ctx2 is the parent of ctx1 */
if (ctx1->parent_ctx == ctx2 && ctx1->parent_gen == ctx2->generation)
return 1;
/*
* If ctx1 and ctx2 have the same parent; we flatten the parent
* hierarchy, see perf_event_init_context().
*/
if (ctx1->parent_ctx && ctx1->parent_ctx == ctx2->parent_ctx &&
ctx1->parent_gen == ctx2->parent_gen)
return 1;
/* Unmatched */
return 0;
}
static void __perf_event_sync_stat(struct perf_event *event,
struct perf_event *next_event)
{
u64 value;
if (!event->attr.inherit_stat)
return;
/*
* Update the event value, we cannot use perf_event_read()
* because we're in the middle of a context switch and have IRQs
* disabled, which upsets smp_call_function_single(), however
* we know the event must be on the current CPU, therefore we
* don't need to use it.
*/
switch (event->state) {
case PERF_EVENT_STATE_ACTIVE:
event->pmu->read(event);
/* fall-through */
case PERF_EVENT_STATE_INACTIVE:
update_event_times(event);
break;
default:
break;
}
/*
* In order to keep per-task stats reliable we need to flip the event
* values when we flip the contexts.
*/
value = local64_read(&next_event->count);
value = local64_xchg(&event->count, value);
local64_set(&next_event->count, value);
swap(event->total_time_enabled, next_event->total_time_enabled);
swap(event->total_time_running, next_event->total_time_running);
/*
* Since we swizzled the values, update the user visible data too.
*/
perf_event_update_userpage(event);
perf_event_update_userpage(next_event);
}
static void perf_event_sync_stat(struct perf_event_context *ctx,
struct perf_event_context *next_ctx)
{
struct perf_event *event, *next_event;
if (!ctx->nr_stat)
return;
update_context_time(ctx);
event = list_first_entry(&ctx->event_list,
struct perf_event, event_entry);
next_event = list_first_entry(&next_ctx->event_list,
struct perf_event, event_entry);
while (&event->event_entry != &ctx->event_list &&
&next_event->event_entry != &next_ctx->event_list) {
__perf_event_sync_stat(event, next_event);
event = list_next_entry(event, event_entry);
next_event = list_next_entry(next_event, event_entry);
}
}
static void perf_event_context_sched_out(struct task_struct *task, int ctxn,
struct task_struct *next)
{
struct perf_event_context *ctx = task->perf_event_ctxp[ctxn];
struct perf_event_context *next_ctx;
struct perf_event_context *parent, *next_parent;
struct perf_cpu_context *cpuctx;
int do_switch = 1;
if (likely(!ctx))
return;
cpuctx = __get_cpu_context(ctx);
if (!cpuctx->task_ctx)
return;
rcu_read_lock();
next_ctx = next->perf_event_ctxp[ctxn];
if (!next_ctx)
goto unlock;
parent = rcu_dereference(ctx->parent_ctx);
next_parent = rcu_dereference(next_ctx->parent_ctx);
/* If neither context have a parent context; they cannot be clones. */
if (!parent && !next_parent)
goto unlock;
if (next_parent == ctx || next_ctx == parent || next_parent == parent) {
/*
* Looks like the two contexts are clones, so we might be
* able to optimize the context switch. We lock both
* contexts and check that they are clones under the
* lock (including re-checking that neither has been
* uncloned in the meantime). It doesn't matter which
* order we take the locks because no other cpu could
* be trying to lock both of these tasks.
*/
raw_spin_lock(&ctx->lock);
raw_spin_lock_nested(&next_ctx->lock, SINGLE_DEPTH_NESTING);
if (context_equiv(ctx, next_ctx)) {
/*
* XXX do we need a memory barrier of sorts
* wrt to rcu_dereference() of perf_event_ctxp
*/
task->perf_event_ctxp[ctxn] = next_ctx;
next->perf_event_ctxp[ctxn] = ctx;
ctx->task = next;
next_ctx->task = task;
do_switch = 0;
perf_event_sync_stat(ctx, next_ctx);
}
raw_spin_unlock(&next_ctx->lock);
raw_spin_unlock(&ctx->lock);
}
unlock:
rcu_read_unlock();
if (do_switch) {
raw_spin_lock(&ctx->lock);
ctx_sched_out(ctx, cpuctx, EVENT_ALL);
cpuctx->task_ctx = NULL;
raw_spin_unlock(&ctx->lock);
}
}
#define for_each_task_context_nr(ctxn) \
for ((ctxn) = 0; (ctxn) < perf_nr_task_contexts; (ctxn)++)
/*
* Called from scheduler to remove the events of the current task,
* with interrupts disabled.
*
* We stop each event and update the event value in event->count.
*
* This does not protect us against NMI, but disable()
* sets the disabled bit in the control field of event _before_
* accessing the event control register. If a NMI hits, then it will
* not restart the event.
*/
void __perf_event_task_sched_out(struct task_struct *task,
struct task_struct *next)
{
int ctxn;
for_each_task_context_nr(ctxn)
perf_event_context_sched_out(task, ctxn, next);
/*
* if cgroup events exist on this CPU, then we need
* to check if we have to switch out PMU state.
* cgroup event are system-wide mode only
*/
if (atomic_read(this_cpu_ptr(&perf_cgroup_events)))
perf_cgroup_sched_out(task, next);
}
static void task_ctx_sched_out(struct perf_event_context *ctx)
{
struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
if (!cpuctx->task_ctx)
return;
if (WARN_ON_ONCE(ctx != cpuctx->task_ctx))
return;
ctx_sched_out(ctx, cpuctx, EVENT_ALL);
cpuctx->task_ctx = NULL;
}
/*
* Called with IRQs disabled
*/
static void cpu_ctx_sched_out(struct perf_cpu_context *cpuctx,
enum event_type_t event_type)
{
ctx_sched_out(&cpuctx->ctx, cpuctx, event_type);
}
static void
ctx_pinned_sched_in(struct perf_event_context *ctx,
struct perf_cpu_context *cpuctx)
{
struct perf_event *event;
list_for_each_entry(event, &ctx->pinned_groups, group_entry) {
if (event->state <= PERF_EVENT_STATE_OFF)
continue;
if (!event_filter_match(event))
continue;
/* may need to reset tstamp_enabled */
if (is_cgroup_event(event))
perf_cgroup_mark_enabled(event, ctx);
if (group_can_go_on(event, cpuctx, 1))
group_sched_in(event, cpuctx, ctx);
/*
* If this pinned group hasn't been scheduled,
* put it in error state.
*/
if (event->state == PERF_EVENT_STATE_INACTIVE) {
update_group_times(event);
event->state = PERF_EVENT_STATE_ERROR;
}
}
}
static void
ctx_flexible_sched_in(struct perf_event_context *ctx,
struct perf_cpu_context *cpuctx)
{
struct perf_event *event;
int can_add_hw = 1;
list_for_each_entry(event, &ctx->flexible_groups, group_entry) {
/* Ignore events in OFF or ERROR state */
if (event->state <= PERF_EVENT_STATE_OFF)
continue;
/*
* Listen to the 'cpu' scheduling filter constraint
* of events:
*/
if (!event_filter_match(event))
continue;
/* may need to reset tstamp_enabled */
if (is_cgroup_event(event))
perf_cgroup_mark_enabled(event, ctx);
if (group_can_go_on(event, cpuctx, can_add_hw)) {
if (group_sched_in(event, cpuctx, ctx))
can_add_hw = 0;
}
}
}
static void
ctx_sched_in(struct perf_event_context *ctx,
struct perf_cpu_context *cpuctx,
enum event_type_t event_type,
struct task_struct *task)
{
u64 now;
int is_active = ctx->is_active;
ctx->is_active |= event_type;
if (likely(!ctx->nr_events))
return;
now = perf_clock();
ctx->timestamp = now;
perf_cgroup_set_timestamp(task, ctx);
/*
* First go through the list and put on any pinned groups
* in order to give them the best chance of going on.
*/
if (!(is_active & EVENT_PINNED) && (event_type & EVENT_PINNED))
ctx_pinned_sched_in(ctx, cpuctx);
/* Then walk through the lower prio flexible groups */
if (!(is_active & EVENT_FLEXIBLE) && (event_type & EVENT_FLEXIBLE))
ctx_flexible_sched_in(ctx, cpuctx);
}
static void cpu_ctx_sched_in(struct perf_cpu_context *cpuctx,
enum event_type_t event_type,
struct task_struct *task)
{
struct perf_event_context *ctx = &cpuctx->ctx;
ctx_sched_in(ctx, cpuctx, event_type, task);
}
static void perf_event_context_sched_in(struct perf_event_context *ctx,
struct task_struct *task)
{
struct perf_cpu_context *cpuctx;
cpuctx = __get_cpu_context(ctx);
if (cpuctx->task_ctx == ctx)
return;
perf_ctx_lock(cpuctx, ctx);
perf_pmu_disable(ctx->pmu);
/*
* We want to keep the following priority order:
* cpu pinned (that don't need to move), task pinned,
* cpu flexible, task flexible.
*/
cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE);
if (ctx->nr_events)
cpuctx->task_ctx = ctx;
perf_event_sched_in(cpuctx, cpuctx->task_ctx, task);
perf_pmu_enable(ctx->pmu);
perf_ctx_unlock(cpuctx, ctx);
}
/*
* When sampling the branck stack in system-wide, it may be necessary
* to flush the stack on context switch. This happens when the branch
* stack does not tag its entries with the pid of the current task.
* Otherwise it becomes impossible to associate a branch entry with a
* task. This ambiguity is more likely to appear when the branch stack
* supports priv level filtering and the user sets it to monitor only
* at the user level (which could be a useful measurement in system-wide
* mode). In that case, the risk is high of having a branch stack with
* branch from multiple tasks. Flushing may mean dropping the existing
* entries or stashing them somewhere in the PMU specific code layer.
*
* This function provides the context switch callback to the lower code
* layer. It is invoked ONLY when there is at least one system-wide context
* with at least one active event using taken branch sampling.
*/
static void perf_branch_stack_sched_in(struct task_struct *prev,
struct task_struct *task)
{
struct perf_cpu_context *cpuctx;
struct pmu *pmu;
unsigned long flags;
/* no need to flush branch stack if not changing task */
if (prev == task)
return;
local_irq_save(flags);
rcu_read_lock();
list_for_each_entry_rcu(pmu, &pmus, entry) {
cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
/*
* check if the context has at least one
* event using PERF_SAMPLE_BRANCH_STACK
*/
if (cpuctx->ctx.nr_branch_stack > 0
&& pmu->flush_branch_stack) {
perf_ctx_lock(cpuctx, cpuctx->task_ctx);
perf_pmu_disable(pmu);
pmu->flush_branch_stack();
perf_pmu_enable(pmu);
perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
}
}
rcu_read_unlock();
local_irq_restore(flags);
}
/*
* Called from scheduler to add the events of the current task
* with interrupts disabled.
*
* We restore the event value and then enable it.
*
* This does not protect us against NMI, but enable()
* sets the enabled bit in the control field of event _before_
* accessing the event control register. If a NMI hits, then it will
* keep the event running.
*/
void __perf_event_task_sched_in(struct task_struct *prev,
struct task_struct *task)
{
struct perf_event_context *ctx;
int ctxn;
for_each_task_context_nr(ctxn) {
ctx = task->perf_event_ctxp[ctxn];
if (likely(!ctx))
continue;
perf_event_context_sched_in(ctx, task);
}
/*
* if cgroup events exist on this CPU, then we need
* to check if we have to switch in PMU state.
* cgroup event are system-wide mode only
*/
if (atomic_read(this_cpu_ptr(&perf_cgroup_events)))
perf_cgroup_sched_in(prev, task);
/* check for system-wide branch_stack events */
if (atomic_read(this_cpu_ptr(&perf_branch_stack_events)))
perf_branch_stack_sched_in(prev, task);
}
static u64 perf_calculate_period(struct perf_event *event, u64 nsec, u64 count)
{
u64 frequency = event->attr.sample_freq;
u64 sec = NSEC_PER_SEC;
u64 divisor, dividend;
int count_fls, nsec_fls, frequency_fls, sec_fls;
count_fls = fls64(count);
nsec_fls = fls64(nsec);
frequency_fls = fls64(frequency);
sec_fls = 30;
/*
* We got @count in @nsec, with a target of sample_freq HZ
* the target period becomes:
*
* @count * 10^9
* period = -------------------
* @nsec * sample_freq
*
*/
/*
* Reduce accuracy by one bit such that @a and @b converge
* to a similar magnitude.
*/
#define REDUCE_FLS(a, b) \
do { \
if (a##_fls > b##_fls) { \
a >>= 1; \
a##_fls--; \
} else { \
b >>= 1; \
b##_fls--; \
} \
} while (0)
/*
* Reduce accuracy until either term fits in a u64, then proceed with
* the other, so that finally we can do a u64/u64 division.
*/
while (count_fls + sec_fls > 64 && nsec_fls + frequency_fls > 64) {
REDUCE_FLS(nsec, frequency);
REDUCE_FLS(sec, count);
}
if (count_fls + sec_fls > 64) {
divisor = nsec * frequency;
while (count_fls + sec_fls > 64) {
REDUCE_FLS(count, sec);
divisor >>= 1;
}
dividend = count * sec;
} else {
dividend = count * sec;
while (nsec_fls + frequency_fls > 64) {
REDUCE_FLS(nsec, frequency);
dividend >>= 1;
}
divisor = nsec * frequency;
}
if (!divisor)
return dividend;
return div64_u64(dividend, divisor);
}
static DEFINE_PER_CPU(int, perf_throttled_count);
static DEFINE_PER_CPU(u64, perf_throttled_seq);
static void perf_adjust_period(struct perf_event *event, u64 nsec, u64 count, bool disable)
{
struct hw_perf_event *hwc = &event->hw;
s64 period, sample_period;
s64 delta;
period = perf_calculate_period(event, nsec, count);
delta = (s64)(period - hwc->sample_period);
delta = (delta + 7) / 8; /* low pass filter */
sample_period = hwc->sample_period + delta;
if (!sample_period)
sample_period = 1;
hwc->sample_period = sample_period;
if (local64_read(&hwc->period_left) > 8*sample_period) {
if (disable)
event->pmu->stop(event, PERF_EF_UPDATE);
local64_set(&hwc->period_left, 0);
if (disable)
event->pmu->start(event, PERF_EF_RELOAD);
}
}
/*
* combine freq adjustment with unthrottling to avoid two passes over the
* events. At the same time, make sure, having freq events does not change
* the rate of unthrottling as that would introduce bias.
*/
static void perf_adjust_freq_unthr_context(struct perf_event_context *ctx,
int needs_unthr)
{
struct perf_event *event;
struct hw_perf_event *hwc;
u64 now, period = TICK_NSEC;
s64 delta;
/*
* only need to iterate over all events iff:
* - context have events in frequency mode (needs freq adjust)
* - there are events to unthrottle on this cpu
*/
if (!(ctx->nr_freq || needs_unthr))
return;
raw_spin_lock(&ctx->lock);
perf_pmu_disable(ctx->pmu);
list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
if (event->state != PERF_EVENT_STATE_ACTIVE)
continue;
if (!event_filter_match(event))
continue;
perf_pmu_disable(event->pmu);
hwc = &event->hw;
if (hwc->interrupts == MAX_INTERRUPTS) {
hwc->interrupts = 0;
perf_log_throttle(event, 1);
event->pmu->start(event, 0);
}
if (!event->attr.freq || !event->attr.sample_freq)
goto next;
/*
* stop the event and update event->count
*/
event->pmu->stop(event, PERF_EF_UPDATE);
now = local64_read(&event->count);
delta = now - hwc->freq_count_stamp;
hwc->freq_count_stamp = now;
/*
* restart the event
* reload only if value has changed
* we have stopped the event so tell that
* to perf_adjust_period() to avoid stopping it
* twice.
*/
if (delta > 0)
perf_adjust_period(event, period, delta, false);
event->pmu->start(event, delta > 0 ? PERF_EF_RELOA