linux-kernel - Re: [PATCH sched_ext/for-6.13-fixes] sched_ext: Fix invalid irq restore in scx_ops

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Message-ID: <Z1n-CEHxgn2YaTVQ@slm.duckdns.org>
Date: Wed, 11 Dec 2024 11:03:04 -1000
From: Tejun Heo <tj@...nel.org>
To: Ihor Solodrai <ihor.solodrai@...me>
Cc: David Vernet <void@...ifault.com>, sched-ext@...a.com,
	kernel-team@...a.com, linux-kernel@...r.kernel.org,
	bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH sched_ext/for-6.13-fixes] sched_ext: Fix invalid irq
 restore in scx_ops_bypass()

On Wed, Dec 11, 2024 at 11:01:51AM -1000, Tejun Heo wrote:
> While adding outer irqsave/restore locking, 0e7ffff1b811 ("scx: Fix raciness
> in scx_ops_bypass()") forgot to convert an inner rq_unlock_irqrestore() to
> rq_unlock() which could re-enable IRQ prematurely leading to the following
> warning:
> 
>   raw_local_irq_restore() called with IRQs enabled
>   WARNING: CPU: 1 PID: 96 at kernel/locking/irqflag-debug.c:10 warn_bogus_irq_restore+0x30/0x40
>   ...
>   Sched_ext: create_dsq (enabling)
>   pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>   pc : warn_bogus_irq_restore+0x30/0x40
>   lr : warn_bogus_irq_restore+0x30/0x40
>   ...
>   Call trace:
>    warn_bogus_irq_restore+0x30/0x40 (P)
>    warn_bogus_irq_restore+0x30/0x40 (L)
>    scx_ops_bypass+0x224/0x3b8
>    scx_ops_enable.isra.0+0x2c8/0xaa8
>    bpf_scx_reg+0x18/0x30
>   ...
>   irq event stamp: 33739
>   hardirqs last  enabled at (33739): [<ffff8000800b699c>] scx_ops_bypass+0x174/0x3b8
>   hardirqs last disabled at (33738): [<ffff800080d48ad4>] _raw_spin_lock_irqsave+0xb4/0xd8
> 
> Drop the stray _irqrestore().
> 
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Reported-by: Ihor Solodrai <ihor.solodrai@...me>
> Link: http://lkml.kernel.org/r/qC39k3UsonrBYD_SmuxHnZIQLsuuccoCrkiqb_BT7DvH945A1_LZwE4g-5Pu9FcCtqZt4lY1HhIPi0homRuNWxkgo1rgP3bkxa0donw8kV4=@pm.me
> Fixes: 0e7ffff1b811 ("scx: Fix raciness in scx_ops_bypass()")
> Cc: stable@...r.kernel.org # v6.12

Applying to sched_ext/for-6.13-fixes.

Thanks.

-- 
tejun