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[134.134.136.24]) by mx.google.com with ESMTPS id b2si7436767pgl.531.2019.03.12.01.00.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 12 Mar 2019 01:00:46 -0700 (PDT) Received-SPF: pass (google.com: domain of jani.nikula@intel.com designates 134.134.136.24 as permitted sender) client-ip=134.134.136.24; Authentication-Results: mx.google.com; spf=pass (google.com: domain of jani.nikula@intel.com designates 134.134.136.24 as permitted sender) smtp.mailfrom=jani.nikula@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 12 Mar 2019 01:00:45 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,470,1544515200"; d="scan'208";a="154206711" Received: from hkrasnod-mobl.ger.corp.intel.com (HELO localhost) ([10.252.62.84]) by fmsmga001.fm.intel.com with ESMTP; 12 Mar 2019 01:00:37 -0700 From: Jani Nikula To: Al Viro , syzbot Cc: airlied@linux.ie, akpm@linux-foundation.org, amir73il@gmail.com, chris@chris-wilson.co.uk, darrick.wong@oracle.com, david@fromorbit.com, dri-devel@lists.freedesktop.org, dvyukov@google.com, eparis@redhat.com, hannes@cmpxchg.org, hughd@google.com, intel-gfx@lists.freedesktop.org, jack@suse.cz, joonas.lahtinen@linux.intel.com, jrdr.linux@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mingo@redhat.com, mszeredi@redhat.com, penguin-kernel@i-love.sakura.ne.jp, peterz@infradead.org, rodrigo.vivi@intel.com, syzkaller-bugs@googlegroups.com, willy@infradead.org Subject: Re: INFO: rcu detected stall in sys_sendfile64 (2) In-Reply-To: <20190312040829.GQ2217@ZenIV.linux.org.uk> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: <00000000000010b2fc057fcdfaba@google.com> <0000000000008c75b50583ddb5f8@google.com> <20190312040829.GQ2217@ZenIV.linux.org.uk> Date: Tue, 12 Mar 2019 10:00:36 +0200 Message-ID: <871s3cfrob.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain 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 Tue, 12 Mar 2019, Al Viro wrote: > On Mon, Mar 11, 2019 at 08:59:00PM -0700, syzbot wrote: >> syzbot has bisected this bug to: >> >> commit 34e07e42c55aeaa78e93b057a6664e2ecde3fadb >> Author: Chris Wilson >> Date: Thu Feb 8 10:54:48 2018 +0000 >> >> drm/i915: Add missing kerneldoc for 'ent' in i915_driver_init_early >> >> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13220283200000 >> start commit: 34e07e42 drm/i915: Add missing kerneldoc for 'ent' in i915.. >> git tree: upstream >> final crash: https://syzkaller.appspot.com/x/report.txt?x=10a20283200000 >> console output: https://syzkaller.appspot.com/x/log.txt?x=17220283200000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=abc3dc9b7a900258 >> dashboard link: https://syzkaller.appspot.com/bug?extid=1505c80c74256c6118a5 >> userspace arch: amd64 >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12c4dc28c00000 >> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15df4108c00000 >> >> Reported-by: syzbot+1505c80c74256c6118a5@syzkaller.appspotmail.com >> Fixes: 34e07e42 ("drm/i915: Add missing kerneldoc for 'ent' in >> i915_driver_init_early") > > Umm... Might be a good idea to add some plausibility filters - it is, > in theory, possible that adding a line in a comment changes behaviour > (without compiler bugs, even - playing with __LINE__ is all it would > take), but the odds that it's _not_ a false positive are very low. If it's not a false positive, it's bound to be good source material for IOCCC. BR, Jani. -- Jani Nikula, Intel Open Source Graphics Center