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[147.11.105.123]) by smtp.gmail.com with ESMTPSA id p66sm7474051pfb.65.2020.05.03.20.35.39 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Sun, 03 May 2020 20:35:46 -0700 (PDT) From: Kevin Hao To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Sebastian Andrzej Siewior , Thomas Gleixner , Steven Rostedt Subject: [PATCH v5.6-rt] mm: slub: Always flush the delayed empty slubs in flush_all() Date: Mon, 4 May 2020 11:34:07 +0800 Message-Id: <20200504033407.2385-1-haokexin@gmail.com> X-Mailer: git-send-email 2.26.0 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable 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: After commit f0b231101c94 ("mm/SLUB: delay giving back empty slubs to IRQ enabled regions"), when the free_slab() is invoked with the IRQ disabled, the empty slubs are moved to a per-CPU list and will be freed after IRQ enabled later. But in the current codes, there is a check to see if there really has the cpu slub on a specific cpu before flushing the delayed empty slubs, this may cause a reference of already released kmem_cache in a scenario like below: cpu 0 cpu 1 kmem_cache_destroy() flush_all() --->IPI flush_cpu_slab() flush_slab() deactivate_slab() discard_slab() free_slab() c->page =3D NULL; for_each_online_cpu(cpu) if (!has_cpu_slab(1, s)) continue this skip to flush the delayed empty slub released by cpu1 kmem_cache_free(kmem_cache, s) kmalloc() __slab_alloc() free_delayed() __free_slab() reference to released kmem_ca= che Fixes: f0b231101c94 ("mm/SLUB: delay giving back empty slubs to IRQ enabl= ed regions") Signed-off-by: Kevin Hao --- mm/slub.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index 15c194ff16e6..83b29bf71fd0 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2402,9 +2402,6 @@ static void flush_all(struct kmem_cache *s) for_each_online_cpu(cpu) { struct slub_free_list *f; =20 - if (!has_cpu_slab(cpu, s)) - continue; - f =3D &per_cpu(slub_free_list, cpu); raw_spin_lock_irq(&f->lock); list_splice_init(&f->list, &tofree); --=20 2.26.0