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([2601:188:c180:4250:ecbe:130d:668d:951d]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-702c4d50f7esm95924946d6.59.2025.07.09.11.28.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 09 Jul 2025 11:28:14 -0700 (PDT) From: Waiman Long X-Google-Original-From: Waiman Long Message-ID: <1f329aff-efd1-4996-9194-9e35030e9faa@redhat.com> Date: Wed, 9 Jul 2025 14:28:13 -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/mutex: Disable preemption in __mutex_unlock_slowpath() To: Linus Torvalds Cc: Peter Zijlstra , Ingo Molnar , Will Deacon , Boqun Feng , Jonathan Corbet , linux-kernel@vger.kernel.org, Jann Horn References: <20250709180550.147205-1-longman@redhat.com> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 7/9/25 2:21 PM, Linus Torvalds wrote: > On Wed, 9 Jul 2025 at 11:19, Linus Torvalds > wrote: >> I absolutely detest the notion of "let's make locking be tied to >> object lifetimes". > Side note: I wonder if there's any way to detect this kind of race in general. > > And I suspect it would involve the exact *opposite* of your patch: > make mutex_unlock() actively cause preemption after it has released > the lock but before it has done the final accesses. I think we can do a a cond_resched() under CONFIG_DEBUG_MUTEXES and CONFIG_KASAN. We certainly don't want to do that with a production kernel. Cheers, Longman