From: Stephen Boyd Date: Thu, 29 Mar 2012 00:10:47 +0000 (-0700) Subject: sched: Fix __schedule_bug() output when called from an interrupt X-Git-Tag: firefly_0821_release~3680^2~3164^2~2 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=6135fc1eb4b1c9ae5f535507ed59591bab51e630;p=firefly-linux-kernel-4.4.55.git sched: Fix __schedule_bug() output when called from an interrupt 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(). [ 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. ] Also-reported-by: Chris Metcalf Signed-off-by: Stephen Boyd Cc: Satyam Sharma Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1332979847-27102-1-git-send-email-sboyd@codeaurora.org Signed-off-by: Ingo Molnar --- diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 9c1629c90b2d..929fd857ef88 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3099,8 +3099,6 @@ 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; @@ -3111,11 +3109,7 @@ 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(); } /*