From mboxrd@z Thu Jan 1 00:00:00 1970 From: Song Liu Subject: Re: [PATCH v4 19/24] raid5: Use sequence counter with associated spinlock Date: Tue, 21 Jul 2020 23:40:16 -0700 Message-ID: References: <20200519214547.352050-1-a.darwish@linutronix.de> <20200720155530.1173732-1-a.darwish@linutronix.de> <20200720155530.1173732-20-a.darwish@linutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <20200720155530.1173732-20-a.darwish@linutronix.de> Sender: linux-raid-owner@vger.kernel.org To: "Ahmed S. Darwish" Cc: Peter Zijlstra , Ingo Molnar , Will Deacon , Thomas Gleixner , "Paul E. McKenney" , "Sebastian A. Siewior" , Steven Rostedt , LKML , linux-raid List-Id: linux-raid.ids On Mon, Jul 20, 2020 at 8:57 AM Ahmed S. Darwish wrote: > > A sequence counter write side critical section must be protected by some > form of locking to serialize writers. A plain seqcount_t does not > contain the information of which lock must be held when entering a write > side critical section. > > Use the new seqcount_spinlock_t data type, which allows to associate a > spinlock with the sequence counter. This enables lockdep to verify that > the spinlock used for writer serialization is held when the write side > critical section is entered. > > If lockdep is disabled this lock association is compiled out and has > neither storage size nor runtime overhead. > > Signed-off-by: Ahmed S. Darwish Acked-by: Song Liu