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Fri, 04 Oct 2019 09:20:50 -0700 (PDT) Received: from pc636 ([37.139.158.167]) by smtp.gmail.com with ESMTPSA id q19sm1341149ljj.73.2019.10.04.09.20.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Oct 2019 09:20:48 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Fri, 4 Oct 2019 18:20:41 +0200 To: Sebastian Andrzej Siewior Cc: Daniel Wagner , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, Andrew Morton , Uladzislau Rezki Subject: Re: [PATCH] mm: vmalloc: Use the vmap_area_lock to protect ne_fit_preload_node Message-ID: <20191004162041.GA30806@pc636> References: <20191003090906.1261-1-dwagner@suse.de> <20191004153728.c5xppuqwqcwecbe6@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191004153728.c5xppuqwqcwecbe6@linutronix.de> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Fri, Oct 04, 2019 at 05:37:28PM +0200, Sebastian Andrzej Siewior wrote: > If you post something that is related to PREEMPT_RT please keep tglx and > me in Cc. > > On 2019-10-03 11:09:06 [+0200], Daniel Wagner wrote: > > Replace preempt_enable() and preempt_disable() with the vmap_area_lock > > spin_lock instead. Calling spin_lock() with preempt disabled is > > illegal for -rt. Furthermore, enabling preemption inside the > > Looking at it again, I have reasonable doubt that this > preempt_disable() is needed. > The intention was to preload a current CPU with one extra object in non-atomic context, thus to use GFP_KERNEL permissive parameters. I.e. that allows us to avoid any allocation(if we stay on the same CPU) when we are in atomic context do splitting. If we have migrate_disable/enable, then, i think preempt_enable/disable should be replaced by it and not the way how it has been proposed in the patch. -- Vlad Rezki