Messages in this thread Patch in this message | | | From | Stephen Boyd <> | Subject | [PATCH] sched: Fix __schedule_bug() output when called from an interrupt | Date | Wed, 28 Mar 2012 17:10:47 -0700 |
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If schedule is called from an interrupt handler __schedule_bug() will call show_regs() with the registers saved during the interrupt handling done in do_IRQ(). This means we'll see the registers and the backtrace for the process that was interrupted and not the full backtrace explaining who called schedule().
This is due to 838225b (sched: use show_regs() to improve __schedule_bug() output, 2007-10-24) which improperly assumed that get_irq_regs() would return the registers for the current stack because it is being called from within an interrupt handler. Simply remove the show_reg() code so that we dump a backtrace for the interrupt handler that called schedule().
Cc: Satyam Sharma <satyam@infradead.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> ---
I ran across this when I was presented with a scheduling while atomic log with a stacktrace pointing at spin_unlock_irqrestore(). It made no sense and I had to guess what interrupt handler could be called and poke around for someone calling schedule() in an interrupt handler. A simple test of putting an msleep() in an interrupt handler works better with this patch because you can actually see the msleep() call in the backtrace.
kernel/sched/core.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 3b4e8b7..b496a0b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3101,8 +3101,6 @@ EXPORT_SYMBOL(sub_preempt_count); */ static noinline void __schedule_bug(struct task_struct *prev) { - struct pt_regs *regs = get_irq_regs(); - if (oops_in_progress) return; @@ -3113,11 +3111,7 @@ static noinline void __schedule_bug(struct task_struct *prev) print_modules(); if (irqs_disabled()) print_irqtrace_events(prev); - - if (regs) - show_regs(regs); - else - dump_stack(); + dump_stack(); } /* -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
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