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([2600:380:6060:12a6:721f:26e:6f8:a9aa]) by smtp.gmail.com with ESMTPSA id w16sm3534007oti.3.2021.10.25.06.36.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 25 Oct 2021 06:36:03 -0700 (PDT) Subject: Re: [syzbot] KCSAN: data-race in sbitmap_queue_clear / sbitmap_queue_clear (3) To: syzbot , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com References: <00000000000089871905cf2b7d09@google.com> From: Jens Axboe Message-ID: Date: Mon, 25 Oct 2021 07:35:59 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <00000000000089871905cf2b7d09@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/25/21 5:16 AM, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 2f111a6fd5b5 Merge tag 'ceph-for-5.15-rc7' of git://github.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=10dae330b00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=b2868748300e5cf6 > dashboard link: https://syzkaller.appspot.com/bug?extid=4f8bfd804b4a1f95b8f6 > compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.2 > > Unfortunately, I don't have any reproducer for this issue yet. > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+4f8bfd804b4a1f95b8f6@syzkaller.appspotmail.com > > ================================================================== > BUG: KCSAN: data-race in sbitmap_queue_clear / sbitmap_queue_clear > > write to 0xffffe8ffffd145b8 of 4 bytes by interrupt on cpu 1: > sbitmap_queue_clear+0xca/0xf0 lib/sbitmap.c:606 > blk_mq_put_tag+0x82/0x90 > __blk_mq_free_request+0x114/0x180 block/blk-mq.c:507 > blk_mq_free_request+0x2c8/0x340 block/blk-mq.c:541 > __blk_mq_end_request+0x214/0x230 block/blk-mq.c:565 > blk_mq_end_request+0x37/0x50 block/blk-mq.c:574 > lo_complete_rq+0xca/0x170 drivers/block/loop.c:541 > blk_complete_reqs block/blk-mq.c:584 [inline] > blk_done_softirq+0x69/0x90 block/blk-mq.c:589 > __do_softirq+0x12c/0x26e kernel/softirq.c:558 > run_ksoftirqd+0x13/0x20 kernel/softirq.c:920 > smpboot_thread_fn+0x22f/0x330 kernel/smpboot.c:164 > kthread+0x262/0x280 kernel/kthread.c:319 > ret_from_fork+0x1f/0x30 > > write to 0xffffe8ffffd145b8 of 4 bytes by interrupt on cpu 0: > sbitmap_queue_clear+0xca/0xf0 lib/sbitmap.c:606 > blk_mq_put_tag+0x82/0x90 > __blk_mq_free_request+0x114/0x180 block/blk-mq.c:507 > blk_mq_free_request+0x2c8/0x340 block/blk-mq.c:541 > __blk_mq_end_request+0x214/0x230 block/blk-mq.c:565 > blk_mq_end_request+0x37/0x50 block/blk-mq.c:574 > lo_complete_rq+0xca/0x170 drivers/block/loop.c:541 > blk_complete_reqs block/blk-mq.c:584 [inline] > blk_done_softirq+0x69/0x90 block/blk-mq.c:589 > __do_softirq+0x12c/0x26e kernel/softirq.c:558 > run_ksoftirqd+0x13/0x20 kernel/softirq.c:920 > smpboot_thread_fn+0x22f/0x330 kernel/smpboot.c:164 > kthread+0x262/0x280 kernel/kthread.c:319 > ret_from_fork+0x1f/0x30 This is just a per-cpu alloc hint, it's racy by nature. What's the preferred way to silence these? -- Jens Axboe