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bh=ncC7o600PU/F6DbooXCSVvIEyJUYp2GOXS0HtlDpoPI=; h=X-UI-Sender-Class:Subject:From:To:Cc:Date:In-Reply-To:References; b=Qcaj5Frqo83OD8IsKGbZpRp4xOGUfKbUYeQT2+/pOe7teISA+wkRCddz/idqYWMRL vLlkaoyhdsMLulQJFsPq4HObgLGFgRFWXqDRkccaevi+3npmCH2d7vyaJi/drJphnj cUB52Ku0Vdg9PoH3l0UO7UpsTM8IyFjH67vEvLHI= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from homer.fritz.box ([185.191.219.22]) by mail.gmx.net (mrgmx105 [212.227.17.168]) with ESMTPSA (Nemesis) id 1MpDJX-1muAN53rCR-00qi60; Tue, 10 Aug 2021 13:47:45 +0200 Message-ID: <2eb3cf340716c40f03a0a342ab40219b3d1de195.camel@gmx.de> Subject: Re: [PATCH v4 29/35] mm: slub: Move flush_cpu_slab() invocations __free_slab() invocations out of IRQ context From: Mike Galbraith To: Vlastimil Babka , Qian Cai , Andrew Morton , Christoph Lameter , David Rientjes , Pekka Enberg , Joonsoo Kim Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sebastian Andrzej Siewior , Thomas Gleixner , Mel Gorman , Jesper Dangaard Brouer , Jann Horn Date: Tue, 10 Aug 2021 13:47:42 +0200 In-Reply-To: References: <20210805152000.12817-1-vbabka@suse.cz> <20210805152000.12817-30-vbabka@suse.cz> <0b36128c-3e12-77df-85fe-a153a714569b@quicinc.com> Content-Type: text/plain; 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dkim=pass header.d=gmx.net header.s=badeba3b8450 header.b=Qcaj5Frq; dmarc=pass (policy=none) header.from=gmx.de; spf=pass (imf19.hostedemail.com: domain of efault@gmx.de designates 212.227.17.20 as permitted sender) smtp.mailfrom=efault@gmx.de X-Stat-Signature: oy5nepuyxizatjnkzgoxm38rktedbwzf X-Rspamd-Queue-Id: 59265B000C16 X-Rspamd-Server: rspam01 X-HE-Tag: 1628596070-721443 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 Tue, 2021-08-10 at 11:03 +0200, Vlastimil Babka wrote: > On 8/9/21 3:41 PM, Qian Cai wrote: > > > =C2=A0 > > > +static DEFINE_MUTEX(flush_lock); > > > +static DEFINE_PER_CPU(struct slub_flush_work, slub_flush); > > > + > > > =C2=A0static void flush_all(struct kmem_cache *s) > > > =C2=A0{ > > > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0on_each_cpu_cond(has_cpu_= slab, flush_cpu_slab, s, 1); > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0struct slub_flush_work *s= fw; > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0unsigned int cpu; > > > + > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0mutex_lock(&flush_lock); > > > > Vlastimil, taking the lock here could trigger a warning during memory = offline/online due to the locking order: > > > > slab_mutex -> flush_lock > > > > [=C2=A0=C2=A0 91.374541] WARNING: possible circular locking dependency= detected > > [=C2=A0=C2=A0 91.381411] 5.14.0-rc5-next-20210809+ #84 Not tainted > > [=C2=A0=C2=A0 91.387149] ---------------------------------------------= --------- > > [=C2=A0=C2=A0 91.394016] lsbug/1523 is trying to acquire lock: > > [=C2=A0=C2=A0 91.399406] ffff800018e76530 (flush_lock){+.+.}-{3:3}, at= : flush_all+0x50/0x1c8 > > [=C2=A0=C2=A0 91.407425] > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0 but task is already holding lock: > > [=C2=A0=C2=A0 91.414638] ffff800018e48468 (slab_mutex){+.+.}-{3:3}, at= : slab_memory_callback+0x44/0x280 > > [=C2=A0=C2=A0 91.423603] > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0 which lock already depends on the new lock. > > > > OK, managed to reproduce in qemu and this fixes it for me on top of > next-20210809. Could you test as well, as your testing might be more > comprehensive? I will format is as a fixup for the proper patch in the s= eries then. As it appeared it should, moving cpu_hotplug_lock outside slab_mutex in kmem_cache_destroy() on top of that silenced the cpu offline gripe. =2D-- mm/slab_common.c | 2 ++ mm/slub.c | 2 +- 2 files changed, 3 insertions(+), 1 deletion(-) =2D-- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -502,6 +502,7 @@ void kmem_cache_destroy(struct kmem_cach if (unlikely(!s)) return; + cpus_read_lock(); mutex_lock(&slab_mutex); s->refcount--; @@ -516,6 +517,7 @@ void kmem_cache_destroy(struct kmem_cach } out_unlock: mutex_unlock(&slab_mutex); + cpus_read_unlock(); } EXPORT_SYMBOL(kmem_cache_destroy); =2D-- a/mm/slub.c +++ b/mm/slub.c @@ -4234,7 +4234,7 @@ int __kmem_cache_shutdown(struct kmem_ca int node; struct kmem_cache_node *n; - flush_all(s); + flush_all_cpus_locked(s); /* Attempt to free all objects */ for_each_kmem_cache_node(s, node, n) { free_partial(s, n);