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From: Joel Fernandes <joel@joelfernandes.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, Zqiang <qiang.zhang1211@gmail.com>,
	Zhen Lei <thunder.leizhen@huaweicloud.com>,
	"Paul E . McKenney" <paulmck@kernel.org>,
	rcu@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 2/2] rcu: Dump vmalloc memory info safely
Date: Sat, 2 Sep 2023 22:05:08 -0400	[thread overview]
Message-ID: <CAEXW_YSk1bE4e30=8+Sqfxeoj-SDesa=bCdyfhNWB+kxkNpXVA@mail.gmail.com> (raw)
In-Reply-To: <CAEXW_YQB4qahh4FZrtw3AOsxwRw7-Bd1YXULCBOE2K9j81Oqag@mail.gmail.com>

On Sat, Sep 2, 2023 at 10:03 PM Joel Fernandes <joel@joelfernandes.org> wrote:
>
> On Sat, Sep 2, 2023 at 9:28 PM Andrew Morton <akpm@linux-foundation.org> wrote:
> >
> > On Wed, 30 Aug 2023 11:04:00 +0000 "Joel Fernandes (Google)" <joel@joelfernandes.org> wrote:
> >
> > > Currently, for double invoke call_rcu(), will dump rcu_head objects
> > > memory info, if the objects is not allocated from the slab allocator,
> > > the vmalloc_dump_obj() will be invoke and the vmap_area_lock spinlock
> > > need to be held, since the call_rcu() can be invoked in interrupt context,
> > > therefore, there is a possibility of spinlock deadlock scenarios.
> > >
> > > And in Preempt-RT kernel, the rcutorture test also trigger the following
> > > lockdep warning:
> >
> > "possibility of deadlock" sounds like something -stable kernels would
> > like to have fixed.
> >
> > Did you consider the desirability of a -stable backport?
> >
> > If so, are we able to identify a suitable Fixes: target?
>
> Good point, it should be:
> Fixes: 98f180837a89 ("mm: Make mem_dump_obj() handle vmalloc() memory")
>
> I am currently reworking the patch as Vlad was also concerned about
> (the existing) issue of accessing vm_struct fields without holding the
> lock [1].
>
> I will add this fixes tag to both patches for the v3 on the respin.
>

Sigh, I missed sharing the link to [1]:
[1] https://lore.kernel.org/all/20230901003321.GA3389909@google.com/

thanks,

 - Joel

  reply	other threads:[~2023-09-03  2:05 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-08-30 11:03 [PATCH 1/2] mm/vmalloc: Add a safer version of find_vm_area() for debug Joel Fernandes (Google)
2023-08-30 11:04 ` [PATCH 2/2] rcu: Dump vmalloc memory info safely Joel Fernandes (Google)
2023-08-30 12:08   ` Matthew Wilcox
2023-09-03  1:28   ` Andrew Morton
2023-09-03  2:03     ` Joel Fernandes
2023-09-03  2:05       ` Joel Fernandes [this message]
2023-08-30 12:07 ` [PATCH 1/2] mm/vmalloc: Add a safer version of find_vm_area() for debug Matthew Wilcox
2023-08-30 12:17   ` Joel Fernandes
2023-08-30 12:48 ` Christoph Hellwig
2023-08-30 13:09   ` Joel Fernandes

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