| Subject: sched: Better debug output for might sleep |
| From: Thomas Gleixner <tglx@linutronix.de> |
| Date: Fri, 05 Oct 2012 08:56:15 +0100 |
| |
| might sleep can tell us where interrupts have been disabled, but we |
| have no idea what disabled preemption. Add some debug infrastructure. |
| |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| --- |
| include/linux/sched.h | 4 ++++ |
| kernel/sched/core.c | 23 +++++++++++++++++++++-- |
| 2 files changed, 25 insertions(+), 2 deletions(-) |
| |
| Index: linux-stable/include/linux/sched.h |
| =================================================================== |
| --- linux-stable.orig/include/linux/sched.h |
| +++ linux-stable/include/linux/sched.h |
| @@ -1624,6 +1624,10 @@ struct task_struct { |
| int kmap_idx; |
| pte_t kmap_pte[KM_TYPE_NR]; |
| #endif |
| + |
| +#ifdef CONFIG_DEBUG_PREEMPT |
| + unsigned long preempt_disable_ip; |
| +#endif |
| }; |
| |
| #ifdef CONFIG_PREEMPT_RT_FULL |
| Index: linux-stable/kernel/sched/core.c |
| =================================================================== |
| --- linux-stable.orig/kernel/sched/core.c |
| +++ linux-stable/kernel/sched/core.c |
| @@ -3311,8 +3311,13 @@ void __kprobes add_preempt_count(int val |
| DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >= |
| PREEMPT_MASK - 10); |
| #endif |
| - if (preempt_count() == val) |
| - trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1)); |
| + if (preempt_count() == val) { |
| + unsigned long ip = get_parent_ip(CALLER_ADDR1); |
| +#ifdef CONFIG_DEBUG_PREEMPT |
| + current->preempt_disable_ip = ip; |
| +#endif |
| + trace_preempt_off(CALLER_ADDR0, ip); |
| + } |
| } |
| EXPORT_SYMBOL(add_preempt_count); |
| |
| @@ -3355,6 +3360,13 @@ static noinline void __schedule_bug(stru |
| print_modules(); |
| if (irqs_disabled()) |
| print_irqtrace_events(prev); |
| +#ifdef DEBUG_PREEMPT |
| + if (in_atomic_preempt_off()) { |
| + pr_err("Preemption disabled at:"); |
| + print_ip_sym(current->preempt_disable_ip); |
| + pr_cont("\n"); |
| + } |
| +#endif |
| dump_stack(); |
| add_taint(TAINT_WARN); |
| } |
| @@ -7700,6 +7712,13 @@ void __might_sleep(const char *file, int |
| debug_show_held_locks(current); |
| if (irqs_disabled()) |
| print_irqtrace_events(current); |
| +#ifdef DEBUG_PREEMPT |
| + if (!preempt_count_equals(preempt_offset)) { |
| + pr_err("Preemption disabled at:"); |
| + print_ip_sym(current->preempt_disable_ip); |
| + pr_cont("\n"); |
| + } |
| +#endif |
| dump_stack(); |
| } |
| EXPORT_SYMBOL(__might_sleep); |