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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id f42sm3621546qta.0.2019.12.04.05.12.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Dec 2019 05:12:03 -0800 (PST) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable From: Qian Cai Mime-Version: 1.0 (1.0) Subject: Re: [PATCH RFC v3 18/36] kmsan: disable LOCK_DEBUGGING_SUPPORT Date: Wed, 4 Dec 2019 08:12:02 -0500 Message-Id: <132F741E-700C-42F4-923E-53454E036E81@lca.pw> References: <20191204122212.ziwntau5hrokrpmk@pathway.suse.cz> Cc: Alexander Potapenko , Steven Rostedt , Marco Elver , Eric Biggers , Christoph Hellwig , Herbert Xu , Harry Wentland , Vegard Nossum , Dmitry Vyukov , Linux Memory Management List , Al Viro , Andreas Dilger , Andrew Morton , Andrey Konovalov , Andrey Ryabinin , Andy Lutomirski , Ard Biesheuvel , Arnd Bergmann , Christoph Hellwig , "Darrick J. Wong" , "David S. Miller" , Dmitry Torokhov , Eric Dumazet , Eric Van Hensbergen , Greg Kroah-Hartman , Ilya Leoshkevich , Ingo Molnar , Jason Wang , Jens Axboe , Marek Szyprowski , Mark Rutland , "Martin K. Petersen" , Martin Schwidefsky , Matthew Wilcox , "Michael S. Tsirkin" , Michal Simek , Randy Dunlap , Robin Murphy , Sergey Senozhatsky , Takashi Iwai , Theodore Ts'o , Thomas Gleixner , Vasily Gorbik , Wolfram Sang In-Reply-To: <20191204122212.ziwntau5hrokrpmk@pathway.suse.cz> To: Petr Mladek X-Mailer: iPhone Mail (17B111) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > On Dec 4, 2019, at 7:22 AM, Petr Mladek wrote: >=20 > IMHO, a generic distro debug kernel could not enable debugging > options that would significantly slow down the kernel. Most users > would refuse using such kernels. Also they might slow down > the system to the point that many problems won't be visible. >=20 > For example, I do not see KASAN enabled in SUSE debug kernel. > I guess that it will be the same with KMSAN. These options > can be enabled in custom kernels when debugging particular > problems. No, KASAN is one of most important debug options to find general issues. It w= as actually used in many debug kernels like those in Google. In contrast, it= will find many issues compared to without even though the performance would= suffer in some degrees. I would even argue that since KASAN is so valuable that it is also desirable= to get KMSAN to work together with KASAN by improving the compilers. Otherw= ise, it is a struggling to choose between KASAN and KMSAN for general debug k= ernels as KASAN could also cover a subset of KMSAN coverage.=