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* [PATCH 1/1] sched: panic, when call schedule with preemption disable
@ 2019-11-21  8:13 YT Chang
  2019-11-21 12:30 ` Peter Zijlstra
  0 siblings, 1 reply; 3+ messages in thread
From: YT Chang @ 2019-11-21  8:13 UTC (permalink / raw)
  To: YT Chang, Peter Zijlstra, Matthias Brugger
  Cc: linux-arm-kernel, linux-mediatek, linux-kernel, wsd_upstream

When preemption is disable, call schedule() is incorrect behavior.
Suggest to panic directly rather than depend on panic_on_warn.

Signed-off-by: YT Chang <yt.chang@mediatek.com>
---
 kernel/sched/core.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 7880f4f..214e8d8 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3861,9 +3861,8 @@ static noinline void __schedule_bug(struct task_struct *prev)
 		print_ip_sym(preempt_disable_ip);
 		pr_cont("\n");
 	}
-	if (panic_on_warn)
-		panic("scheduling while atomic\n");
 
+	panic("scheduling while atomic\n");
 	dump_stack();
 	add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
 }
-- 
1.9.1
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^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH 1/1] sched: panic, when call schedule with preemption disable
  2019-11-21  8:13 [PATCH 1/1] sched: panic, when call schedule with preemption disable YT Chang
@ 2019-11-21 12:30 ` Peter Zijlstra
  2019-11-26 13:11   ` Kathleen Chang
  0 siblings, 1 reply; 3+ messages in thread
From: Peter Zijlstra @ 2019-11-21 12:30 UTC (permalink / raw)
  To: YT Chang
  Cc: Matthias Brugger, linux-mediatek, linux-kernel, wsd_upstream,
	linux-arm-kernel

On Thu, Nov 21, 2019 at 04:13:05PM +0800, YT Chang wrote:
> When preemption is disable, call schedule() is incorrect behavior.
> Suggest to panic directly rather than depend on panic_on_warn.

Why!?

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^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH 1/1] sched: panic, when call schedule with preemption disable
  2019-11-21 12:30 ` Peter Zijlstra
@ 2019-11-26 13:11   ` Kathleen Chang
  0 siblings, 0 replies; 3+ messages in thread
From: Kathleen Chang @ 2019-11-26 13:11 UTC (permalink / raw)
  To: Peter Zijlstra
  Cc: Matthias Brugger, linux-mediatek, linux-kernel, wsd_upstream,
	linux-arm-kernel

On Thu, 2019-11-21 at 13:30 +0100, Peter Zijlstra wrote:
> On Thu, Nov 21, 2019 at 04:13:05PM +0800, YT Chang wrote:
> > When preemption is disable, call schedule() is incorrect behavior.
> > Suggest to panic directly rather than depend on panic_on_warn.
> 
> Why!?


1. Panic directly will easily find the root cause. 

   Call scheduling in atomic affects not only performance but also
system stability. 
    ex: 
      Call scheduling in IRQ will result in IRQ enable after schedule() 

2. A lot of warnings depend on panic_on_warn. It is not practical to
set panic_on_warn=1. 

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^ permalink raw reply	[flat|nested] 3+ messages in thread

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2019-11-21  8:13 [PATCH 1/1] sched: panic, when call schedule with preemption disable YT Chang
2019-11-21 12:30 ` Peter Zijlstra
2019-11-26 13:11   ` Kathleen Chang

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