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Date: Thu, 11 Jan 2024 04:36:02 -0800
From: Andi Kleen <ak@linux.intel.com>
To: Marco Elver <elver@google.com>
Cc: Oscar Salvador <osalvador@suse.de>, andrey.konovalov@linux.dev,
	Andrew Morton <akpm@linux-foundation.org>,
	Andrey Konovalov <andreyknvl@gmail.com>,
	Alexander Potapenko <glider@google.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	Vlastimil Babka <vbabka@suse.cz>, kasan-dev@googlegroups.com,
	Evgenii Stepanov <eugenis@google.com>, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org,
	Andrey Konovalov <andreyknvl@google.com>
Subject: Re: [PATCH v4 12/22] lib/stackdepot: use read/write lock
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> stackdepot is severely limited in what kernel facilities it may use
> due to being used by such low level facilities as the allocator
> itself.

RCU can be done quite low level too (e.g. there is NMI safe RCU)

> 
> I've been suggesting percpu-rwsem here, but looking at it in more
> detail that doesn't work because percpu-rwsem wants to sleep, but
> stackdepot must work in non-sleepable contexts. :-/

Yes something per CPU would work too I suppose. We used to have
big reader spinlocks for this. 

-Andi