From: Vlastimil Babka <vbabka@suse.cz>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Rongwei Wang <rongwei.wang@linux.alibaba.com>,
Christoph Lameter <cl@linux.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
David Rientjes <rientjes@google.com>,
Pekka Enberg <penberg@kernel.org>,
Hyeonggon Yoo <42.hyeyoo@gmail.com>,
Roman Gushchin <roman.gushchin@linux.dev>,
linux-mm@kvack.org, Thomas Gleixner <tglx@linutronix.de>,
Mike Galbraith <efault@gmx.de>
Subject: Re: [PATCH v2 5/5] mm/slub: simplify __cmpxchg_double_slab() and slab_[un]lock()
Date: Thu, 25 Aug 2022 14:59:22 +0200 [thread overview]
Message-ID: <fcaf5a93-5376-1504-e8e5-a795401fe34c@suse.cz> (raw)
In-Reply-To: <YwZQ9k6bkLRQlzc6@linutronix.de>
On 8/24/22 18:25, Sebastian Andrzej Siewior wrote:
> On 2022-08-23 19:04:00 [+0200], Vlastimil Babka wrote:
>> The PREEMPT_RT specific disabling of irqs in __cmpxchg_double_slab()
>> (through slab_[un]lock()) is unnecessary as bit_spin_lock() disables
>> preemption and that's sufficient on RT where interrupts are threaded.
>
> maybe something like
> "… sufficient on PREEMPT_RT where no allocation/ free operation is
> performed in hardirq context and so interrupt the current operation."
>
>> That means we no longer need the slab_[un]lock() wrappers, so delete
>> them and rename the current __slab_[un]lock() to slab_[un]lock().
>>
>> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
>> Acked-by: David Rientjes <rientjes@google.com>
>
> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Thanks, incorporated your wording suggestions.
>> --- a/mm/slub.c
>> +++ b/mm/slub.c
>> @@ -454,7 +454,7 @@ static __always_inline void __slab_lock(struct slab *slab)
> …
>> /*
>> * Interrupts must be disabled (for the fallback code to work right), typically
>> - * by an _irqsave() lock variant. Except on PREEMPT_RT where locks are different
>> - * so we disable interrupts as part of slab_[un]lock().
>> + * by an _irqsave() lock variant. Except on PREEMPT_RT where these variants do
>> + * not actually disable interrupts. On the other hand the migrate_disable()
>> + * done by bit_spin_lock() is sufficient on PREEMPT_RT thanks to its threaded
>> + * interrupts.
>
> " On PREEMPT_RT the
> preempt_disable(), which is part of bit_spin_lock(), is sufficient
> because the policy is not to allow any allocation/ free operation in
> hardirq context. Therefore nothing can interrupt the operation."
>
> This also includes SMP function calls (IPI).
>
>> */
>> static inline bool __cmpxchg_double_slab(struct kmem_cache *s, struct slab *slab,
>> void *freelist_old, unsigned long counters_old,
>
> Sebastian
next prev parent reply other threads:[~2022-08-25 12:59 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-23 17:03 [PATCH v2 0/5] mm/slub: fix validation races and cleanup locking Vlastimil Babka
2022-08-23 17:03 ` [PATCH v2 1/5] mm/slub: move free_debug_processing() further Vlastimil Babka
2022-08-23 17:03 ` [PATCH v2 2/5] mm/slub: restrict sysfs validation to debug caches and make it safe Vlastimil Babka
2022-08-24 4:41 ` Hyeonggon Yoo
2022-08-23 17:03 ` [PATCH v2 3/5] mm/slub: remove slab_lock() usage for debug operations Vlastimil Babka
2022-08-23 17:03 ` [PATCH v2 4/5] mm/slub: convert object_map_lock to non-raw spinlock Vlastimil Babka
2022-08-24 15:53 ` Sebastian Andrzej Siewior
2022-08-23 17:04 ` [PATCH v2 5/5] mm/slub: simplify __cmpxchg_double_slab() and slab_[un]lock() Vlastimil Babka
2022-08-24 10:24 ` Hyeonggon Yoo
2022-08-24 11:51 ` Vlastimil Babka
2022-08-24 12:45 ` Hyeonggon Yoo
2022-08-24 16:31 ` Sebastian Andrzej Siewior
2022-08-24 13:04 ` Hyeonggon Yoo
2022-08-25 12:41 ` Vlastimil Babka
2022-08-24 16:25 ` Sebastian Andrzej Siewior
2022-08-25 12:59 ` Vlastimil Babka [this message]
2022-08-25 7:51 ` [PATCH 6/5] slub: Make PREEMPT_RT support less convoluted Sebastian Andrzej Siewior
2022-08-25 8:41 ` Vlastimil Babka
2022-08-25 8:49 ` Hyeonggon Yoo
2022-08-25 13:16 ` [PATCH v2 0/5] mm/slub: fix validation races and cleanup locking Vlastimil Babka
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