sched/core: Panic on scheduling while atomic bugs if kernel.panic_on_warn is set

Daniel Bristot de Oliveira · Ingo Molnar · commit 748c7201e622 · 2016-07-10T20:17:27.000+02:00
Currently, a schedule while atomic error prints the stack trace to the kernel log and the system continue running. Although it is possible to collect the kernel log messages and analyze it, often more information are needed. Furthermore, keep the system running is not always the best choice. For example, when the preempt count underflows the system will not stop to complain about scheduling while atomic, so the kernel log can wrap around overwriting the first stack trace, tuning the analysis even more challenging. This patch uses the kernel.panic_on_warn sysctl to help out on these more complex situations. When kernel.panic_on_warn is set to 1, the kernel will panic() in the schedule while atomic detection. The default value of the sysctl is 0, maintaining the current behavior. Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com> Reviewed-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Luis Claudio R. Goncalves <lgoncalv@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/e8f7b80f353aa22c63bd8557208163989af8493d.1464983675.git.bristot@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
@@ -3168,6 +3168,9 @@ static noinline void __schedule_bug(struct task_struct *prev)
 		pr_cont("\n");
 	}
 #endif
+	if (panic_on_warn)
+		panic("scheduling while atomic\n");
+
 	dump_stack();
 	add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
 }

Original file line number	Diff line number	Diff line change
`@@ -3168,6 +3168,9 @@ static noinline void __schedule_bug(struct task_struct *prev)`
`3168`	`3168`	`pr_cont("\n");`
`3169`	`3169`	`}`
`3170`	`3170`	`#endif`
	`3171`	`+ if (panic_on_warn)`
	`3172`	`+ panic("scheduling while atomic\n");`
	`3173`	`+`
`3171`	`3174`	`dump_stack();`
`3172`	`3175`	`add_taint(TAINT_WARN, LOCKDEP_STILL_OK);`
`3173`	`3176`	`}`