| From ccc31edd0d03b63bf64d188a4d899ef1f832b822 Mon Sep 17 00:00:00 2001 |
| From: Eric Dumazet <edumazet@google.com> |
| Date: Mon, 4 Jun 2012 00:18:19 +0000 |
| Subject: [PATCH] drop_monitor: dont sleep in atomic context |
| |
| commit bec4596b4e6770c7037f21f6bd27567b152dc0d6 upstream. |
| |
| drop_monitor calls several sleeping functions while in atomic context. |
| |
| BUG: sleeping function called from invalid context at mm/slub.c:943 |
| in_atomic(): 1, irqs_disabled(): 0, pid: 2103, name: kworker/0:2 |
| Pid: 2103, comm: kworker/0:2 Not tainted 3.5.0-rc1+ #55 |
| Call Trace: |
| [<ffffffff810697ca>] __might_sleep+0xca/0xf0 |
| [<ffffffff811345a3>] kmem_cache_alloc_node+0x1b3/0x1c0 |
| [<ffffffff8105578c>] ? queue_delayed_work_on+0x11c/0x130 |
| [<ffffffff815343fb>] __alloc_skb+0x4b/0x230 |
| [<ffffffffa00b0360>] ? reset_per_cpu_data+0x160/0x160 [drop_monitor] |
| [<ffffffffa00b022f>] reset_per_cpu_data+0x2f/0x160 [drop_monitor] |
| [<ffffffffa00b03ab>] send_dm_alert+0x4b/0xb0 [drop_monitor] |
| [<ffffffff810568e0>] process_one_work+0x130/0x4c0 |
| [<ffffffff81058249>] worker_thread+0x159/0x360 |
| [<ffffffff810580f0>] ? manage_workers.isra.27+0x240/0x240 |
| [<ffffffff8105d403>] kthread+0x93/0xa0 |
| [<ffffffff816be6d4>] kernel_thread_helper+0x4/0x10 |
| [<ffffffff8105d370>] ? kthread_freezable_should_stop+0x80/0x80 |
| [<ffffffff816be6d0>] ? gs_change+0xb/0xb |
| |
| Rework the logic to call the sleeping functions in right context. |
| |
| Use standard timer/workqueue api to let system chose any cpu to perform |
| the allocation and netlink send. |
| |
| Also avoid a loop if reset_per_cpu_data() cannot allocate memory : |
| use mod_timer() to wait 1/10 second before next try. |
| |
| Signed-off-by: Eric Dumazet <edumazet@google.com> |
| Cc: Neil Horman <nhorman@tuxdriver.com> |
| Reviewed-by: Neil Horman <nhorman@tuxdriver.com> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| [PG: diffstat here is less by one line due to blank line removal] |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| --- |
| net/core/drop_monitor.c | 101 ++++++++++++++++-------------------------------- |
| 1 file changed, 33 insertions(+), 68 deletions(-) |
| |
| diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c |
| index 58c57fcc67ad..cd3f2b942991 100644 |
| --- a/net/core/drop_monitor.c |
| +++ b/net/core/drop_monitor.c |
| @@ -33,9 +33,6 @@ |
| #define TRACE_ON 1 |
| #define TRACE_OFF 0 |
| |
| -static void send_dm_alert(struct work_struct *unused); |
| - |
| - |
| /* |
| * Globals, our netlink socket pointer |
| * and the work handle that will send up |
| @@ -45,11 +42,10 @@ static int trace_state = TRACE_OFF; |
| static DEFINE_MUTEX(trace_state_mutex); |
| |
| struct per_cpu_dm_data { |
| - struct work_struct dm_alert_work; |
| - struct sk_buff /* __rcu <-- only 2.6.37+ */ *skb; |
| - atomic_t dm_hit_count; |
| - struct timer_list send_timer; |
| - int cpu; |
| + spinlock_t lock; |
| + struct sk_buff *skb; |
| + struct work_struct dm_alert_work; |
| + struct timer_list send_timer; |
| }; |
| |
| struct dm_hw_stat_delta { |
| @@ -75,13 +71,13 @@ static int dm_delay = 1; |
| static unsigned long dm_hw_check_delta = 2*HZ; |
| static LIST_HEAD(hw_stats_list); |
| |
| -static void reset_per_cpu_data(struct per_cpu_dm_data *data) |
| +static struct sk_buff *reset_per_cpu_data(struct per_cpu_dm_data *data) |
| { |
| size_t al; |
| struct net_dm_alert_msg *msg; |
| struct nlattr *nla; |
| struct sk_buff *skb; |
| - struct sk_buff *oskb = rcu_dereference_protected(data->skb, 1); |
| + unsigned long flags; |
| |
| al = sizeof(struct net_dm_alert_msg); |
| al += dm_hit_limit * sizeof(struct net_dm_drop_point); |
| @@ -96,65 +92,40 @@ static void reset_per_cpu_data(struct per_cpu_dm_data *data) |
| sizeof(struct net_dm_alert_msg)); |
| msg = nla_data(nla); |
| memset(msg, 0, al); |
| - } else |
| - schedule_work_on(data->cpu, &data->dm_alert_work); |
| - |
| - /* |
| - * Don't need to lock this, since we are guaranteed to only |
| - * run this on a single cpu at a time. |
| - * Note also that we only update data->skb if the old and new skb |
| - * pointers don't match. This ensures that we don't continually call |
| - * synchornize_rcu if we repeatedly fail to alloc a new netlink message. |
| - */ |
| - if (skb != oskb) { |
| - rcu_assign_pointer(data->skb, skb); |
| - |
| - synchronize_rcu(); |
| - |
| - atomic_set(&data->dm_hit_count, dm_hit_limit); |
| + } else { |
| + mod_timer(&data->send_timer, jiffies + HZ / 10); |
| } |
| |
| + spin_lock_irqsave(&data->lock, flags); |
| + swap(data->skb, skb); |
| + spin_unlock_irqrestore(&data->lock, flags); |
| + |
| + return skb; |
| } |
| |
| -static void send_dm_alert(struct work_struct *unused) |
| +static void send_dm_alert(struct work_struct *work) |
| { |
| struct sk_buff *skb; |
| - struct per_cpu_dm_data *data = &get_cpu_var(dm_cpu_data); |
| + struct per_cpu_dm_data *data; |
| |
| - WARN_ON_ONCE(data->cpu != smp_processor_id()); |
| + data = container_of(work, struct per_cpu_dm_data, dm_alert_work); |
| |
| - /* |
| - * Grab the skb we're about to send |
| - */ |
| - skb = rcu_dereference_protected(data->skb, 1); |
| - |
| - /* |
| - * Replace it with a new one |
| - */ |
| - reset_per_cpu_data(data); |
| + skb = reset_per_cpu_data(data); |
| |
| - /* |
| - * Ship it! |
| - */ |
| if (skb) |
| genlmsg_multicast(skb, 0, NET_DM_GRP_ALERT, GFP_KERNEL); |
| - |
| - put_cpu_var(dm_cpu_data); |
| } |
| |
| /* |
| * This is the timer function to delay the sending of an alert |
| * in the event that more drops will arrive during the |
| - * hysteresis period. Note that it operates under the timer interrupt |
| - * so we don't need to disable preemption here |
| + * hysteresis period. |
| */ |
| -static void sched_send_work(unsigned long unused) |
| +static void sched_send_work(unsigned long _data) |
| { |
| - struct per_cpu_dm_data *data = &get_cpu_var(dm_cpu_data); |
| - |
| - schedule_work_on(smp_processor_id(), &data->dm_alert_work); |
| + struct per_cpu_dm_data *data = (struct per_cpu_dm_data *)_data; |
| |
| - put_cpu_var(dm_cpu_data); |
| + schedule_work(&data->dm_alert_work); |
| } |
| |
| static void trace_drop_common(struct sk_buff *skb, void *location) |
| @@ -164,22 +135,17 @@ static void trace_drop_common(struct sk_buff *skb, void *location) |
| struct nlattr *nla; |
| int i; |
| struct sk_buff *dskb; |
| - struct per_cpu_dm_data *data = &get_cpu_var(dm_cpu_data); |
| - |
| + struct per_cpu_dm_data *data; |
| + unsigned long flags; |
| |
| - rcu_read_lock(); |
| - dskb = rcu_dereference(data->skb); |
| + local_irq_save(flags); |
| + data = &__get_cpu_var(dm_cpu_data); |
| + spin_lock(&data->lock); |
| + dskb = data->skb; |
| |
| if (!dskb) |
| goto out; |
| |
| - if (!atomic_add_unless(&data->dm_hit_count, -1, 0)) { |
| - /* |
| - * we're already at zero, discard this hit |
| - */ |
| - goto out; |
| - } |
| - |
| nlh = (struct nlmsghdr *)dskb->data; |
| nla = genlmsg_data(nlmsg_data(nlh)); |
| msg = nla_data(nla); |
| @@ -189,7 +155,8 @@ static void trace_drop_common(struct sk_buff *skb, void *location) |
| goto out; |
| } |
| } |
| - |
| + if (msg->entries == dm_hit_limit) |
| + goto out; |
| /* |
| * We need to create a new entry |
| */ |
| @@ -201,13 +168,11 @@ static void trace_drop_common(struct sk_buff *skb, void *location) |
| |
| if (!timer_pending(&data->send_timer)) { |
| data->send_timer.expires = jiffies + dm_delay * HZ; |
| - add_timer_on(&data->send_timer, smp_processor_id()); |
| + add_timer(&data->send_timer); |
| } |
| |
| out: |
| - rcu_read_unlock(); |
| - put_cpu_var(dm_cpu_data); |
| - return; |
| + spin_unlock_irqrestore(&data->lock, flags); |
| } |
| |
| static void trace_kfree_skb_hit(struct sk_buff *skb, void *location) |
| @@ -416,11 +381,11 @@ static int __init init_net_drop_monitor(void) |
| |
| for_each_present_cpu(cpu) { |
| data = &per_cpu(dm_cpu_data, cpu); |
| - data->cpu = cpu; |
| INIT_WORK(&data->dm_alert_work, send_dm_alert); |
| init_timer(&data->send_timer); |
| - data->send_timer.data = cpu; |
| + data->send_timer.data = (unsigned long)data; |
| data->send_timer.function = sched_send_work; |
| + spin_lock_init(&data->lock); |
| reset_per_cpu_data(data); |
| } |
| |
| -- |
| 1.8.5.2 |
| |