From: Qian Cai <quic_qiancai@quicinc.com>
To: Vlastimil Babka <vbabka@suse.cz>, Mike Galbraith <efault@gmx.de>,
Andrew Morton <akpm@linux-foundation.org>,
Christoph Lameter <cl@linux.com>,
David Rientjes <rientjes@google.com>,
Pekka Enberg <penberg@kernel.org>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Thomas Gleixner <tglx@linutronix.de>,
Mel Gorman <mgorman@techsingularity.net>,
Jesper Dangaard Brouer <brouer@redhat.com>,
Jann Horn <jannh@google.com>
Subject: Re: [PATCH v4 29/35] mm: slub: Move flush_cpu_slab() invocations __free_slab() invocations out of IRQ context
Date: Mon, 9 Aug 2021 18:13:57 -0400 [thread overview]
Message-ID: <eca69b61-13cd-474d-f02c-05131494ce3a@quicinc.com> (raw)
In-Reply-To: <7d9ac614-f18e-de5d-2d47-f92e618d76fc@suse.cz>
On 8/9/2021 4:08 PM, Vlastimil Babka wrote:
> On 8/9/2021 8:44 PM, Mike Galbraith wrote:
>> On Mon, 2021-08-09 at 09:41 -0400, Qian Cai wrote:
>>>
>>>
>>> On 8/5/2021 11:19 AM, Vlastimil Babka wrote:
>>>>
>>>>
>>>> +static DEFINE_MUTEX(flush_lock);
>>>> +static DEFINE_PER_CPU(struct slub_flush_work, slub_flush);
>>>> +
>>>> static void flush_all(struct kmem_cache *s)
>>>> {
>>>> - on_each_cpu_cond(has_cpu_slab, flush_cpu_slab, s, 1);
>>>> + struct slub_flush_work *sfw;
>>>> + unsigned int cpu;
>>>> +
>>>> + mutex_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
>>
>> Bugger. That chain ending with cpu_hotplug_lock makes slub_cpu_dead()
>> taking slab_mutex a non-starter for cpu hotplug as well. It's
>> established early by kernel_init_freeable()..kmem_cache_destroy() as
>> well as by slab_mem_going_offline_callback().
>
> I suck at reading the lockdep splats, so I don't see yet how the "existing
> reverse order" occurs - I do understand the order in the "lsbug".
> What I also wonder is why didn't this occur also in the older RT trees with this
> patch. I did change the order of locks in flush_all() to take flush_lock first
> and cpus_read_lock() second, as Cyrill Gorcunov suggested. Would the original
> order prevent this? Or we would fail anyway because we already took
> cpus_read_lock() in offline_pages() and now are taking it again - do these nest
> or not?
"lsbug" is just an user-space tool running workloads like memory offline/online
via sysfs. The splat indicated that the existing locking orders on the running
system saw so far are:
flush_lock -> cpu_hotplug_lock (in #1)
cpu_hotplug_lock -> pck_batch_high_lock (in #2)
pcp_batch_high_lock -> (memory_chain).rwsem (in #3)
(memory_chain).rwsem -> slab_mutex (in #4)
Thus, lockdep inferences that taking flush_lock first could later reaching
slab_mutex. Then, in the commit, memory offline (in #0) started to take the locking
order slab_mutex -> flush_lock. Thus, the potential deadlock warning.
next prev parent reply other threads:[~2021-08-09 22:14 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-05 15:19 [PATCH v4 00/35] SLUB: reduce irq disabled scope and make it RT compatible Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 01/35] mm, slub: don't call flush_all() from slab_debug_trace_open() Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 02/35] mm, slub: allocate private object map for debugfs listings Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 03/35] mm, slub: allocate private object map for validate_slab_cache() Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 04/35] mm, slub: don't disable irq for debug_check_no_locks_freed() Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 05/35] mm, slub: remove redundant unfreeze_partials() from put_cpu_partial() Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 06/35] mm, slub: unify cmpxchg_double_slab() and __cmpxchg_double_slab() Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 07/35] mm, slub: extract get_partial() from new_slab_objects() Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 08/35] mm, slub: dissolve new_slab_objects() into ___slab_alloc() Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 09/35] mm, slub: return slab page from get_partial() and set c->page afterwards Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 10/35] mm, slub: restructure new page checks in ___slab_alloc() Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 11/35] mm, slub: simplify kmem_cache_cpu and tid setup Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 12/35] mm, slub: move disabling/enabling irqs to ___slab_alloc() Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 13/35] mm, slub: do initial checks in ___slab_alloc() with irqs enabled Vlastimil Babka
2021-08-15 10:14 ` Vlastimil Babka
2021-08-15 10:22 ` Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 14/35] mm, slub: move disabling irqs closer to get_partial() in ___slab_alloc() Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 15/35] mm, slub: restore irqs around calling new_slab() Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 16/35] mm, slub: validate slab from partial list or page allocator before making it cpu slab Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 17/35] mm, slub: check new pages with restored irqs Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 18/35] mm, slub: stop disabling irqs around get_partial() Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 19/35] mm, slub: move reset of c->page and freelist out of deactivate_slab() Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 20/35] mm, slub: make locking in deactivate_slab() irq-safe Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 21/35] mm, slub: call deactivate_slab() without disabling irqs Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 22/35] mm, slub: move irq control into unfreeze_partials() Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 23/35] mm, slub: discard slabs in unfreeze_partials() without irqs disabled Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 24/35] mm, slub: detach whole partial list at once in unfreeze_partials() Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 25/35] mm, slub: separate detaching of partial list in unfreeze_partials() from unfreezing Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 26/35] mm, slub: only disable irq with spin_lock in __unfreeze_partials() Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 27/35] mm, slub: don't disable irqs in slub_cpu_dead() Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 28/35] mm, slab: make flush_slab() possible to call with irqs enabled Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 29/35] mm: slub: Move flush_cpu_slab() invocations __free_slab() invocations out of IRQ context Vlastimil Babka
2021-08-09 13:41 ` Qian Cai
2021-08-09 18:44 ` Mike Galbraith
2021-08-09 20:08 ` Vlastimil Babka
2021-08-09 22:13 ` Qian Cai [this message]
2021-08-10 1:07 ` Mike Galbraith
2021-08-10 9:03 ` Vlastimil Babka
2021-08-10 11:47 ` Mike Galbraith
2021-08-10 20:31 ` Paul E. McKenney
2021-08-10 22:36 ` Vlastimil Babka
2021-08-10 23:53 ` Paul E. McKenney
2021-08-11 14:17 ` Paul E. McKenney
2021-08-10 20:25 ` Paul E. McKenney
2021-08-10 14:33 ` Vlastimil Babka
2021-08-11 1:42 ` Qian Cai
2021-08-11 8:55 ` Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 30/35] mm: slub: Make object_map_lock a raw_spinlock_t Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 31/35] mm, slub: optionally save/restore irqs in slab_[un]lock()/ Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 32/35] mm, slub: make slab_lock() disable irqs with PREEMPT_RT Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 33/35] mm, slub: protect put_cpu_partial() with disabled irqs instead of cmpxchg Vlastimil Babka
2021-08-05 15:19 ` [PATCH v4 34/35] mm, slub: use migrate_disable() on PREEMPT_RT Vlastimil Babka
2021-08-05 15:20 ` [PATCH v4 35/35] mm, slub: convert kmem_cpu_slab protection to local_lock Vlastimil Babka
2021-08-15 12:27 ` Sven Eckelmann
2021-08-17 8:37 ` Vlastimil Babka
2021-08-17 9:12 ` Sebastian Andrzej Siewior
2021-08-17 9:17 ` Vlastimil Babka
2021-08-17 9:31 ` Sebastian Andrzej Siewior
2021-08-17 9:31 ` Vlastimil Babka
2021-08-17 9:34 ` Sebastian Andrzej Siewior
2021-08-17 9:13 ` Vlastimil Babka
2021-08-17 10:14 ` Vlastimil Babka
2021-08-17 19:53 ` Andrew Morton
2021-08-18 11:52 ` Vlastimil Babka
2021-08-23 20:36 ` Thomas Gleixner
2021-08-17 15:39 ` Sebastian Andrzej Siewior
2021-08-17 15:41 ` Vlastimil Babka
2021-08-17 15:49 ` Sebastian Andrzej Siewior
2021-08-17 15:56 ` Vlastimil Babka
2021-08-05 16:42 ` [PATCH v4 00/35] SLUB: reduce irq disabled scope and make it RT compatible Sebastian Andrzej Siewior
2021-08-06 5:14 ` Mike Galbraith
2021-08-06 7:45 ` Vlastimil Babka
2021-08-10 14:36 ` Vlastimil Babka
2021-08-15 10:18 ` Vlastimil Babka
2021-08-17 10:23 ` Vlastimil Babka
2021-08-17 15:59 ` Vlastimil Babka
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