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Thu, 12 Jun 2025 22:52:55 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGfT3vZmyWBhXW9Py11Ri5qfbIXpcGOdhc8T4lJJRvwqujl2GDwJOVyYUgmO+X3YgxyQOhGaQ== X-Received: by 2002:a05:6e02:1786:b0:3dc:7660:9ed9 with SMTP id e9e14a558f8ab-3de00a267c9mr18607045ab.0.1749793964593; Thu, 12 Jun 2025 22:52:44 -0700 (PDT) Received: from [192.168.21.4] ([216.228.39.50]) by smtp.gmail.com with ESMTPSA id 8926c6da1cb9f-50149c85ef9sm155867173.119.2025.06.12.22.52.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 12 Jun 2025 22:52:43 -0700 (PDT) From: Waiman Long X-Google-Original-From: Waiman Long Message-ID: <7a006014-bf6e-4480-bd61-b0333c74e3a4@redhat.com> Date: Fri, 13 Jun 2025 01:52:43 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] locking/rwsem: use OWNER_NONSPINNABLE directly instead of OWNER_SPINNABLE To: alexjlzheng@gmail.com, peterz@infradead.org, will@kernel.org, boqun.feng@gmail.com Cc: linux-kernel@vger.kernel.org, Jinliang Zheng References: <20250610130158.4876-1-alexjlzheng@tencent.com> Content-Language: en-US In-Reply-To: <20250610130158.4876-1-alexjlzheng@tencent.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 6/10/25 9:01 AM, alexjlzheng@gmail.com wrote: > From: Jinliang Zheng > > After commit 7d43f1ce9dd0 ("locking/rwsem: Enable time-based spinning on > reader-owned rwsem"), OWNER_SPINNABLE contains all possible values except > OWNER_NONSPINNABLE, namely OWNER_NULL | OWNER_WRITER | OWNER_READER. > > Therefore, it is better to use OWNER_NONSPINNABLE directly to determine > whether to exit optimistic spin. > > And, remove useless OWNER_SPINNABLE to simplify the code. > > Signed-off-by: Jinliang Zheng > --- > kernel/locking/rwsem.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c > index 2ddb827e3bea..8572dba95af4 100644 > --- a/kernel/locking/rwsem.c > +++ b/kernel/locking/rwsem.c > @@ -727,8 +727,6 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem) > return ret; > } > > -#define OWNER_SPINNABLE (OWNER_NULL | OWNER_WRITER | OWNER_READER) > - > static inline enum owner_state > rwsem_owner_state(struct task_struct *owner, unsigned long flags) > { > @@ -835,7 +833,7 @@ static bool rwsem_optimistic_spin(struct rw_semaphore *sem) > enum owner_state owner_state; > > owner_state = rwsem_spin_on_owner(sem); > - if (!(owner_state & OWNER_SPINNABLE)) > + if (owner_state == OWNER_NONSPINNABLE) > break; > > /* Right, OWNER_SPINNABLE is no longer needed after commit 7d43f1ce9dd0. Acked-by: Waiman Long