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Message-ID: <15f8fbd8-2dbc-3df7-c748-c76e3479e227@I-love.SAKURA.ne.jp>
Date: Wed, 13 Sep 2023 23:30:23 +0900
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To: Hillf Danton <hdanton@...a.com>,
Sanan Hasanov <Sanan.Hasanov@....edu>,
Thomas Gleixner <tglx@...utronix.de>, peterz@...radead.org
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
syzkaller@...glegroups.com, LKML <linux-kernel@...r.kernel.org>
Subject: Re: BUG: soft lockup in smp_call_function
On 2023/09/13 20:07, Hillf Danton wrote:
>
> cpu1 cpu4 (see below)
> ==== ====
> drm_crtc_vblank_off __run_hrtimer
> spin_lock_irq(&dev->event_lock);
> ...
> drm_handle_vblank
> hrtimer_cancel spin_lock_irqsave(&dev->event_lock, irqflags);
>
>
> Deadlock should have been reported instead provided the lockdep_map in
> struct timer_list were added also to hrtimer, so it is highly appreciated
> if Tetsuo or Thomas adds it before 6.8 or 6.10.
Not me. ;-)
Since hrtimer_cancel() retries forever until lock_hrtimer_base() succeeds,
we want to add a lockdep annotation into hrtimer_cancel() so that we can
detect this type of deadlock?
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