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[209.85.167.53]) by smtp.gmail.com with ESMTPSA id u67sm9610415lja.78.2019.11.11.10.50.38 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 11 Nov 2019 10:50:39 -0800 (PST) Received: by mail-lf1-f53.google.com with SMTP id v8so10655703lfa.12 for ; Mon, 11 Nov 2019 10:50:38 -0800 (PST) X-Received: by 2002:a19:c790:: with SMTP id x138mr16826204lff.61.1573498238697; Mon, 11 Nov 2019 10:50:38 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Linus Torvalds Date: Mon, 11 Nov 2019 10:50:22 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: KCSAN: data-race in __alloc_file / __alloc_file To: Eric Dumazet Cc: Alan Stern , Marco Elver , Eric Dumazet , syzbot , linux-fsdevel , Linux Kernel Mailing List , syzkaller-bugs , Al Viro , Andrea Parri , "Paul E. McKenney" , LKMM Maintainers -- Akira Yokosawa Content-Type: text/plain; charset="UTF-8" Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Archived-At: List-Archive: List-Post: On Mon, Nov 11, 2019 at 10:31 AM Eric Dumazet wrote: > > Problem is that KASAN/KCSAN stops as soon as one issue is hit, > regardless of it being a false positive or not. So mayb e that - together with the known huge base of false positives - just means that KCSAN needs some more work before it can be used as a basis for sending out patches. Maybe the reporting needs to create a hash of the location, and report once per location? Or something like that. Maybe KCSAN needs a way to filter out known false positives on a KCSAN side, without having to change the source for a tool that gives too much noise? > If we do not annotate the false positive, the real issues might be > hidden for years. I don't think "change the kernel source for a tool that isn't good enough" is the solution. > There is no pattern really, only a lot of noise (small ' bugs' that > have no real impact) Yeah, if it hasn't shown any real bugs so far, that just strengthens the "it needs much fewer false positives to be useful". KASAN and lockdep can afford to stop after the first problem, because the problems they report - and the additional annotations you might want to add - are quality problems and annotations. Linus