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McKenney" , Metin Kaya , Xuewen Yan , K Prateek Nayak , Thomas Gleixner , Daniel Lezcano , Suleiman Souhlal , kernel-team@android.com, Connor O'Brien Subject: Re: [PATCH v16 3/7] locking/mutex: Add p->blocked_on wrappers for correctness checks Message-ID: References: <20250412060258.3844594-1-jstultz@google.com> <20250412060258.3844594-4-jstultz@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250412060258.3844594-4-jstultz@google.com> Hi John, On 11/04/25 23:02, John Stultz wrote: > From: Valentin Schneider > > This lets us assert mutex::wait_lock is held whenever we access > p->blocked_on, as well as warn us for unexpected state changes. > > Cc: Joel Fernandes > Cc: Qais Yousef > Cc: Ingo Molnar > Cc: Peter Zijlstra > Cc: Juri Lelli > Cc: Vincent Guittot > Cc: Dietmar Eggemann > Cc: Valentin Schneider > Cc: Steven Rostedt > Cc: Ben Segall > Cc: Zimuzo Ezeozue > Cc: Mel Gorman > Cc: Will Deacon > Cc: Waiman Long > Cc: Boqun Feng > Cc: "Paul E. McKenney" > Cc: Metin Kaya > Cc: Xuewen Yan > Cc: K Prateek Nayak > Cc: Thomas Gleixner > Cc: Daniel Lezcano > Cc: Suleiman Souhlal > Cc: kernel-team@android.com > Signed-off-by: Valentin Schneider > [fix conflicts, call in more places] > Signed-off-by: Connor O'Brien > [jstultz: tweaked commit subject, reworked a good bit] > Signed-off-by: John Stultz > --- ... > +static inline struct mutex *__get_task_blocked_on(struct task_struct *p) > +{ > + return READ_ONCE(p->blocked_on); > +} > + Shouldn't we check that wait_lock is held also when reading blocked_on? And, if that's the case, why do we use READ_ONCE? Thanks, Juri