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c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1661358676; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=mprJIov31xPyXL15UhFizTSu2Y/hCOuo3zqhTrVAL0c=; b=QJOnulx4YpMgaVWcANWrBLjnihF8vGFrRSBu3ky3ym1Erb2gTZNqdXIuRUBN4ABj+f6wds qgguoQ9f8vUcFDAQ== From: Sebastian Andrzej Siewior To: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Vlastimil Babka , Rongwei Wang , Christoph Lameter , Joonsoo Kim , David Rientjes , Pekka Enberg , Roman Gushchin , linux-mm@kvack.org, Thomas Gleixner , Mike Galbraith Subject: Re: [PATCH v2 5/5] mm/slub: simplify __cmpxchg_double_slab() and slab_[un]lock() Message-ID: References: <20220823170400.26546-1-vbabka@suse.cz> <20220823170400.26546-6-vbabka@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=linutronix.de header.s=2020 header.b=pSd+vMUI; 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dkim=pass header.d=linutronix.de header.s=2020 header.b=pSd+vMUI; dkim=pass header.d=linutronix.de header.s=2020e header.b=QJOnulx4; spf=pass (imf24.hostedemail.com: domain of bigeasy@linutronix.de designates 193.142.43.55 as permitted sender) smtp.mailfrom=bigeasy@linutronix.de; dmarc=pass (policy=none) header.from=linutronix.de X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: A0181180067 X-Stat-Signature: 76qmemju17yk899eaastxyh9woxqpht7 X-HE-Tag: 1661358677-244253 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 > > Acked-by: David Rientjes Sebastian