From: Andrew Morton <akpm@linux-foundation.org>
To: Waiman Long <longman@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 3/3] mm/slub: Fix potential deadlock problem in slab_attr_store()
Date: Mon, 10 Feb 2020 15:10:08 -0800 [thread overview]
Message-ID: <20200210151008.1c1d74c1876e363b729f5b1c@linux-foundation.org> (raw)
In-Reply-To: <0cb70f4a-7fa0-5567-02fc-955e0406a4e7@redhat.com>
On Mon, 10 Feb 2020 17:14:31 -0500 Waiman Long <longman@redhat.com> wrote:
> >> --- a/mm/slub.c
> >> +++ b/mm/slub.c
> >> @@ -5536,7 +5536,12 @@ static ssize_t slab_attr_store(struct kobject *kobj,
> >> if (slab_state >= FULL && err >= 0 && is_root_cache(s)) {
> >> struct kmem_cache *c;
> >>
> >> - mutex_lock(&slab_mutex);
> >> + /*
> >> + * Timeout after 100ms
> >> + */
> >> + if (mutex_timed_lock(&slab_mutex, 100) < 0)
> >> + return -EBUSY;
> >> +
> > Oh dear. Surely there's a better fix here. Does slab really need to
> > hold slab_mutex while creating that sysfs file? Why?
> >
> > If the issue is two threads trying to create the same sysfs file
> > (unlikely, given that both will need to have created the same cache)
> > then can we add a new mutex specifically for this purpose?
> >
> > Or something else.
> >
> Well, the current code iterates all the memory cgroups to set the same
> value in all of them. I believe the reason for holding the slab mutex is
> to make sure that memcg hierarchy is stable during this iteration
> process.
But that is unrelated to creation of the sysfs file?
next prev parent reply other threads:[~2020-02-10 23:10 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-10 20:46 [PATCH 0/3] locking/mutex: Add mutex_timed_lock() to solve potential deadlock problems Waiman Long
2020-02-10 20:46 ` [PATCH 1/3] locking/mutex: Add mutex_timed_lock() Waiman Long
2020-02-10 20:46 ` [PATCH 2/3] locking/mutex: Enable some lock event counters Waiman Long
2020-02-10 20:46 ` [PATCH 3/3] mm/slub: Fix potential deadlock problem in slab_attr_store() Waiman Long
2020-02-10 22:03 ` Andrew Morton
2020-02-10 22:14 ` Waiman Long
2020-02-10 23:10 ` Andrew Morton [this message]
2020-02-11 23:30 ` Waiman Long
2020-02-12 20:40 ` Waiman Long
2020-02-13 12:22 ` kbuild test robot
2020-02-13 16:48 ` kbuild test robot
2020-02-11 12:31 ` [PATCH 0/3] locking/mutex: Add mutex_timed_lock() to solve potential deadlock problems Peter Zijlstra
2020-02-11 23:31 ` Waiman Long
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