From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@gentwo.de>,
linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Matthew Wilcox <willy@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Pekka Enberg <penberg@kernel.org>,
linux-mm@kvack.org
Subject: Re: [PATCH 1/9] slub: Make PREEMPT_RT support less convoluted
Date: Thu, 18 Aug 2022 17:22:53 +0200 [thread overview]
Message-ID: <Yv5ZTXMmk9LupRae@linutronix.de> (raw)
In-Reply-To: <5679405a-b3c3-6dc5-783f-7ebeda7c9bf0@suse.cz>
On 2022-08-18 16:37:06 [+0200], Vlastimil Babka wrote:
> > The slub fastpath does not interfere with slow path operations and the
>
> That's true on !PREEMPT_RT because a slowpath operation under
> local_lock_irqsave() will disable interrupts, so there can't be a
> fastpath operation in an interrupt handler appearing in the middle of a
> slowpath operation.
>
> On PREEMPT_RT local_lock_irqsave() doesn't actually disable interrupts,
> so that can happen. IIRC we learned that the hard way when Mike
> Galbraith was testing early versions of my PREEMPT_RT changes for SLUB.
I think the point is that local_lock_irqsave() does not disable
preemption. So the lock owner (within the local_lock_irqsave() section)
can be preempted and another task can use the fast path which does not
involve the lock and things go boom from here.
Sebastian
next prev parent reply other threads:[~2022-08-18 21:10 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20220817162703.728679-1-bigeasy@linutronix.de>
2022-08-17 16:26 ` Sebastian Andrzej Siewior
2022-08-18 9:42 ` Christoph Lameter
2022-08-18 14:37 ` Vlastimil Babka
2022-08-18 15:22 ` Sebastian Andrzej Siewior [this message]
2022-08-19 15:04 ` Christoph Lameter
2022-08-25 5:15 ` Hyeonggon Yoo
2022-08-18 17:34 ` Linus Torvalds
2022-08-23 17:15 ` Vlastimil Babka
2022-08-24 13:25 ` Sebastian Andrzej Siewior
2022-08-24 13:54 ` Vlastimil Babka
2022-08-24 13:57 ` Sebastian Andrzej Siewior
2022-08-17 16:26 ` [PATCH 4/9] mm/vmstat: Use preempt_[dis|en]able_nested() Sebastian Andrzej Siewior
2022-08-17 16:26 ` [PATCH 5/9] mm/debug: Provide VM_WARN_ON_IRQS_ENABLED() Sebastian Andrzej Siewior
2022-08-17 16:27 ` [PATCH 6/9] mm/memcontrol: Replace the PREEMPT_RT conditionals Sebastian Andrzej Siewior
2022-08-17 16:59 ` Johannes Weiner
2022-08-18 2:45 ` Muchun Song
2022-08-17 16:27 ` [PATCH 7/9] mm/compaction: Get rid of RT ifdeffery Sebastian Andrzej Siewior
2022-08-18 8:55 ` Rasmus Villemoes
2022-08-18 15:51 ` Sebastian Andrzej Siewior
2022-08-24 13:50 ` Thomas Gleixner
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