linux-kernel - [PATCH] sched: Panic on scheduling while atomic if kernel.panic_on

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Message-Id: <e8f7b80f353aa22c63bd8557208163989af8493d.1464983675.git.bristot@redhat.com>
Date:	Fri,  3 Jun 2016 17:10:18 -0300
From:	Daniel Bristot de Oliveira <bristot@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	"Luis Claudio R. Goncalves" <lgoncalv@...hat.com>
Subject: [PATCH] sched: Panic on scheduling while atomic if kernel.panic_on_warn is set

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.

Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Christian Borntraeger <borntraeger@...ibm.com>
Cc: "Luis Claudio R. Goncalves" <lgoncalv@...hat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@...hat.com>
---
 kernel/sched/core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 7f2cae4..7d07ed9 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3146,6 +3146,9 @@ 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);
 }
-- 
2.5.5