Re: [PATCH AUTOSEL 5.9 27/39] sched/idle: Fix arch_cpu_idle() vs tracing

Sasha Levin
2020-12-13T14:11:56Z

On Thu, Dec 03, 2020 at 06:10:15PM +0100, Peter Zijlstra wrote:
>On Thu, Dec 03, 2020 at 03:54:42PM +0100, Heiko Carstens wrote:
>> On Thu, Dec 03, 2020 at 08:28:21AM -0500, Sasha Levin wrote:
>> > From: Peter Zijlstra <peterz@infradead.org>
>> >
>> > [ Upstream commit 58c644ba512cfbc2e39b758dd979edd1d6d00e27 ]
>> >
>> > We call arch_cpu_idle() with RCU disabled, but then use
>> > local_irq_{en,dis}able(), which invokes tracing, which relies on RCU.
>> >
>> > Switch all arch_cpu_idle() implementations to use
>> > raw_local_irq_{en,dis}able() and carefully manage the
>> > lockdep,rcu,tracing state like we do in entry.
>> >
>> > (XXX: we really should change arch_cpu_idle() to not return with
>> > interrupts enabled)
>> >
>> > Reported-by: Sven Schnelle <svens@linux.ibm.com>
>> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>> > Reviewed-by: Mark Rutland <mark.rutland@arm.com>
>> > Tested-by: Mark Rutland <mark.rutland@arm.com>
>> > Link: https://lkml.kernel.org/r/20201120114925.594122626@infradead.org
>> > Signed-off-by: Sasha Levin <sashal@kernel.org>
>>
>> This patch broke s390 irq state tracing. A patch to fix this is
>> scheduled to be merged upstream today (hopefully).
>> Therefore I think this patch should not yet go into 5.9 stable.
>
>Agreed.

I'll also grab b1cae1f84a0f ("s390: fix irq state tracing"). Thanks!

--
Thanks,
Sasha