From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Hillf Danton <hdanton@sina.com>
Cc: Mike Galbraith <efault@gmx.de>,
Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
linux-rt-users <linux-rt-users@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Skeggs <bskeggs@redhat.com>
Subject: Re: kvm+nouveau induced lockdep gripe
Date: Mon, 26 Oct 2020 18:31:07 +0100 [thread overview]
Message-ID: <20201026173107.quylcy6fgjvrqat6@linutronix.de> (raw)
In-Reply-To: <20201024050000.8104-1-hdanton@sina.com>
On 2020-10-24 13:00:00 [+0800], Hillf Danton wrote:
>
> Hmm...curious how that word went into your mind. And when?
> > [ 30.457363]
> > other info that might help us debug this:
> > [ 30.457369] Possible unsafe locking scenario:
> >
> > [ 30.457375] CPU0
> > [ 30.457378] ----
> > [ 30.457381] lock(&mgr->vm_lock);
> > [ 30.457386] <Interrupt>
> > [ 30.457389] lock(&mgr->vm_lock);
> > [ 30.457394]
> > *** DEADLOCK ***
> >
> > <snips 999 lockdep lines and zillion ATOMIC_SLEEP gripes>
The backtrace contained the "normal" vm_lock. What should follow is the
backtrace of the in-softirq usage.
>
> Dunno if blocking softint is a right cure.
>
> --- a/drivers/gpu/drm/drm_vma_manager.c
> +++ b/drivers/gpu/drm/drm_vma_manager.c
> @@ -229,6 +229,7 @@ EXPORT_SYMBOL(drm_vma_offset_add);
> void drm_vma_offset_remove(struct drm_vma_offset_manager *mgr,
> struct drm_vma_offset_node *node)
> {
> + local_bh_disable();
There is write_lock_bh(). However changing only one will produce the
same backtrace somewhere else unless all other users already run BH
disabled region.
> write_lock(&mgr->vm_lock);
>
> if (drm_mm_node_allocated(&node->vm_node)) {
Sebastian
next prev parent reply other threads:[~2020-10-26 17:31 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20201021125324.ualpvrxvzyie6d7d@linutronix.de>
2020-10-21 13:14 ` [ANNOUNCE] v5.9.1-rt18 Sebastian Andrzej Siewior
2020-10-27 6:53 ` Fernando Lopez-Lezcano
2020-10-27 8:22 ` Sebastian Andrzej Siewior
2020-10-27 17:07 ` Fernando Lopez-Lezcano
2020-10-28 20:24 ` Sebastian Andrzej Siewior
2020-10-22 5:21 ` ltp or kvm triggerable lockdep alloc_pid() deadlock gripe Mike Galbraith
2020-10-22 16:44 ` Sebastian Andrzej Siewior
2020-10-22 5:28 ` kvm+nouveau induced lockdep gripe Mike Galbraith
2020-10-23 9:01 ` Sebastian Andrzej Siewior
2020-10-23 12:07 ` Mike Galbraith
[not found] ` <20201024022236.19608-1-hdanton@sina.com>
2020-10-24 3:38 ` Mike Galbraith
[not found] ` <20201024050000.8104-1-hdanton@sina.com>
2020-10-24 5:25 ` Mike Galbraith
[not found] ` <20201024094224.2804-1-hdanton@sina.com>
2020-10-26 17:26 ` Sebastian Andrzej Siewior
2020-10-26 17:31 ` Sebastian Andrzej Siewior [this message]
2020-10-26 19:15 ` Mike Galbraith
2020-10-26 19:53 ` Sebastian Andrzej Siewior
2020-10-27 6:03 ` Mike Galbraith
2020-10-27 9:00 ` Sebastian Andrzej Siewior
2020-10-27 9:49 ` Mike Galbraith
2020-10-27 10:14 ` Mike Galbraith
2020-10-27 10:18 ` Sebastian Andrzej Siewior
2020-10-27 11:13 ` Mike Galbraith
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