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[94.245.46.49]) by smtp.gmail.com with ESMTPSA id z12sm1244lfh.61.2020.07.14.13.06.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Jul 2020 13:06:19 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Tue, 14 Jul 2020 22:06:16 +0200 To: Sebastian Andrzej Siewior Cc: "Paul E. McKenney" , mingo@kernel.org, linux-kernel@vger.kernel.org, rcu@vger.kernel.org, arnd@arndb.de, elver@google.com, ethp@qq.com, frederic@kernel.org, jbi.octave@gmail.com, joel@joelfernandes.org, lihaoliang@google.com, madhuparnabhowmik10@gmail.com, mchehab+huawei@kernel.org, peter.enderborg@sony.com, rdunlap@infradead.org, richard.weiyang@linux.alibaba.com, urezki@gmail.com, zou_wei@huawei.com, tglx@linutronix.de Subject: Re: [GIT PULL tip/core/rcu] RCU commits for v5.9 Message-ID: <20200714200616.GA20137@pc636> References: <20200714172701.GA31369@paulmck-ThinkPad-P72> <20200714181426.hhguqzrcqdubyvae@linutronix.de> <20200714182732.GU9247@paulmck-ThinkPad-P72> <20200714190253.ylqjif7frqs2rq7x@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200714190253.ylqjif7frqs2rq7x@linutronix.de> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 14, 2020 at 09:02:53PM +0200, Sebastian Andrzej Siewior wrote: > On 2020-07-14 11:27:32 [-0700], Paul E. McKenney wrote: > > I believe that Ulad and Joel are working on an update. > > I expressed multiple times that I am unhappy with the raw_spinlock_t > which both want to keep. It is important to be future proof but at the > same time I am not sure if they know how many in-hardirq kmalloc() or > kfree() invocation we have as of today in PREEMPT_RT. > It is not about counting how many times kfree_rcu() gets called from the hard IRQ context for RT kernel. In fact it is about breaking of such possibility if a conversion to spinlock_t is done. Is not it? As a result the revert would change a behavior of the API function, that is used to accept such usage. That is a motivation. -- Vlad Rezki