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[94.245.46.49]) by smtp.gmail.com with ESMTPSA id h22sm8680500ljb.65.2020.05.04.09.56.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 May 2020 09:56:32 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Mon, 4 May 2020 18:56:29 +0200 To: "Paul E. McKenney" Cc: Uladzislau Rezki , Joel Fernandes , LKML , linux-mm@kvack.org, Andrew Morton , "Theodore Y . Ts'o" , Matthew Wilcox , RCU , Oleksiy Avramchenko Subject: Re: [PATCH 19/24] rcu/tree: Support reclaim for head-less object Message-ID: <20200504165629.GA20257@pc636> References: <20200428205903.61704-1-urezki@gmail.com> <20200428205903.61704-20-urezki@gmail.com> <20200501223909.GF7560@paulmck-ThinkPad-P72> <20200504001258.GD197097@google.com> <20200504002855.GF2869@paulmck-ThinkPad-P72> <20200504003237.GD212435@google.com> <20200504142153.GG17577@pc636> <20200504153147.GL2869@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200504153147.GL2869@paulmck-ThinkPad-P72> 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: > > > > For single argument we can drop the lock before the entry to the page > > allocator. Because it follows might_sleep() anotation we avoid of having > > a situation when spinlock(rt mutex) is taken from any atomic context. > > > > Since the lock is dropped the current context can be interrupted by > > an IRQ which in its turn can also call kvfree_rcu() on current CPU. > > In that case it must be double argument(single is not allowed) kvfree_rcu() > > call. For PREEMPT_RT if no cache everything is reverted to rcu_head usage, > > i.e. the entry to page allocator is bypassed. > > > > It can be addressed as a separate patch and send out later on if we > > are on the same page. > > > > Paul, Joel what are your opinions? > > I strongly prefer that it be removed from the series. I do understand > that this is a bit more hassle right now, but this does help avoid > confusion in the future, plus perhaps also avoiding issues with future > bisections. > We have already decided to get rid of it, i mean small allocations(dynamic rcu_head attaching). I will exclude it from next patch-set version. -- Vlad Rezki