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Shutemov" To: Yu Zhao Cc: Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Tetsuo Handa , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 3/4] mm: avoid slub allocation while holding list_lock Message-ID: <20190912100429.fk5er66aostbtvyi@box> References: <20190912004401.jdemtajrspetk3fh@box> <20190912023111.219636-1-yuzhao@google.com> <20190912023111.219636-3-yuzhao@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190912023111.219636-3-yuzhao@google.com> User-Agent: NeoMutt/20180716 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Sep 11, 2019 at 08:31:10PM -0600, Yu Zhao wrote: > If we are already under list_lock, don't call kmalloc(). Otherwise we > will run into deadlock because kmalloc() also tries to grab the same > lock. > > Fixing the problem by using a static bitmap instead. > > WARNING: possible recursive locking detected > -------------------------------------------- > mount-encrypted/4921 is trying to acquire lock: > (&(&n->list_lock)->rlock){-.-.}, at: ___slab_alloc+0x104/0x437 > > but task is already holding lock: > (&(&n->list_lock)->rlock){-.-.}, at: __kmem_cache_shutdown+0x81/0x3cb > > other info that might help us debug this: > Possible unsafe locking scenario: > > CPU0 > ---- > lock(&(&n->list_lock)->rlock); > lock(&(&n->list_lock)->rlock); > > *** DEADLOCK *** > > Signed-off-by: Yu Zhao Acked-by: Kirill A. Shutemov -- Kirill A. Shutemov