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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>,
	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>,
	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: Wed, 24 Aug 2022 18:31:14 +0200	[thread overview]
Message-ID: <YwZSUpYY9l442Lxr@linutronix.de> (raw)
In-Reply-To: <YwX8VPptgCLkuP6i@hyeyoo>

On 2022-08-24 19:24:20 [+0900], Hyeonggon Yoo wrote:
> I'm not familiar with PREEMPT_RT preemption model so not sure I'm following.
> 
> 1) Does "interrupts are threaded on RT" mean processing _most_ (all handlers
>    that did not specified IRQF_NO_THREAD) of interrupts are delayed to irq threads
>    and processed later in process context, and the kernel *never* use
>    spinlock_t, local_lock_t that does not disable interrupts (and sleep) on RT
>    in hardware/software interrupt context?

All non-threaded interrupts (or everything in hardirq context) must not
allocate (even with GFP_ATOMIC) or free memory on PREEMPT_RT. This is
policy. If you refer by "software interrupt" to softirqs then they can
allocate memory since softirq is also threaded.

> BTW Is there a good documentation/papers on PREEMPT_RT preemption model?
> I tried to find but only found Documentation/locking/locktypes.rst :(

What is it, that you are looking for? But the locking description is
good ;)

> Thanks!
> 
> > Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> > Acked-by: David Rientjes <rientjes@google.com>

Sebastian


  parent reply	other threads:[~2022-08-24 16:31 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 [this message]
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
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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