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[209.51.188.17]) by mx.google.com with ESMTPS id w18si19670303ybk.396.2021.01.25.19.12.38 for (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Mon, 25 Jan 2021 19:12:38 -0800 (PST) Received-SPF: pass (google.com: domain of qemu-devel-bounces+patch=linaro.org@nongnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; Authentication-Results: mx.google.com; dkim=pass header.i=@163.com header.s=s110527 header.b=mWsL+DG2; spf=pass (google.com: domain of qemu-devel-bounces+patch=linaro.org@nongnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom="qemu-devel-bounces+patch=linaro.org@nongnu.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=163.com Received: from localhost ([::1]:59910 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l4EmT-0007zg-Qw for patch@linaro.org; Mon, 25 Jan 2021 22:12:37 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:51908) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from <08005325@163.com>) id 1l4EmH-0007ur-KO; Mon, 25 Jan 2021 22:12:25 -0500 Received: from m12-17.163.com ([220.181.12.17]:56708) by eggs.gnu.org with esmtps (TLS1.2:DHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from <08005325@163.com>) id 1l4EmA-0001TP-Fh; Mon, 25 Jan 2021 22:12:24 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:Subject:Date:Message-Id:MIME-Version; bh=ARGFx 3eyFgOKdRTd52qxfbeghKpqzDB6AglisdeUAPo=; b=mWsL+DG2k88SzLNPawj9h h+9P8L/wgBhz2AkVRNF2rbhPanvBrl0X53Z3At+fIeE6x3dRT7m1Dyu3VF8fs6fx PA1CCprVTt4+29c0yZlkPsKlO5oEbUEzR1AC+F+1xh58EXymimMjB99pibDhxJof hky+wOe6hl8GV08OtjdDls= Received: from localhost.localdomain (unknown [116.228.45.98]) by smtp13 (Coremail) with SMTP id EcCowADnnkaAiA9gprz_hg--.47925S2; Tue, 26 Jan 2021 11:12:00 +0800 (CST) From: 08005325@163.com To: kwolf@redhat.com, mreitz@redhat.com, jsnow@redhat.com Subject: [PATCH v2] Fix crash with IOthread when block commit after snapshot Date: Tue, 26 Jan 2021 11:11:44 +0800 Message-Id: <20210126031144.13121-1-08005325@163.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210125120727.7799-1-08005325@163.com> References: <20210125120727.7799-1-08005325@163.com> MIME-Version: 1.0 X-CM-TRANSID: EcCowADnnkaAiA9gprz_hg--.47925S2 X-Coremail-Antispam: 1Uf129KBjvJXoWxZw43Cw13Jw1DCw13CFWxWFg_yoWrKw18pr yUWFnakw40kFn7ZFs2y3WIgry5Kw40vF4DCwnrtr18ur9xA3WxKFyrArWYgFWjq3yfJr4q qF12ga48tFn5A3DanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07j9jjgUUUUU= X-Originating-IP: [116.228.45.98] X-CM-SenderInfo: qqyqikqtsvqiywtou0bp/1tbiGQAmrFyPbtCX5gAAsP Received-SPF: pass client-ip=220.181.12.17; envelope-from=08005325@163.com; helo=m12-17.163.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FROM=0.001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Michael Qiu , qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+patch=linaro.org@nongnu.org Sender: "Qemu-devel" From: Michael Qiu v2: modify the coredump backtrace within commit log with the newest qemu with master branch Currently, if guest has workloads, IO thread will acquire aio_context lock before do io_submit, it leads to segmentfault when do block commit after snapshot. Just like below: Program received signal SIGSEGV, Segmentation fault. [Switching to Thread 0x7f7c7d91f700 (LWP 99907)] 0x00005576d0f65aab in bdrv_mirror_top_pwritev at ../block/mirror.c:1437 1437 ../block/mirror.c: No such file or directory. (gdb) p s->job $17 = (MirrorBlockJob *) 0x0 (gdb) p s->stop $18 = false (gdb) bt Program received signal SIGSEGV, Segmentation fault. [Switching to Thread 0x7f7c7d91f700 (LWP 99907)] 0x00005576d0f65aab in bdrv_mirror_top_pwritev at ../block/mirror.c:1437 1437 ../block/mirror.c: No such file or directory. (gdb) bt #0 0x00005576d0f65aab in bdrv_mirror_top_pwritev at ../block/mirror.c:1437 #1 0x00005576d0f7f3ab in bdrv_driver_pwritev at ../block/io.c:1174 #2 0x00005576d0f8139d in bdrv_aligned_pwritev at ../block/io.c:1988 #3 0x00005576d0f81b65 in bdrv_co_pwritev_part at ../block/io.c:2156 #4 0x00005576d0f8e6b7 in blk_do_pwritev_part at ../block/block-backend.c:1260 #5 0x00005576d0f8e84d in blk_aio_write_entry at ../block/block-backend.c:1476 #6 0x00005576d1060ddb in coroutine_trampoline at ../util/coroutine-ucontext.c:173 #7 0x00007f7c8d3be0d0 in __start_context at /lib/../lib64/libc.so.6 #8 0x00007f7b52beb1e0 in () #9 0x0000000000000000 in () Switch to qemu main thread: #0 0x00007f903be704ed in __lll_lock_wait at /lib/../lib64/libpthread.so.0 #1 0x00007f903be6bde6 in _L_lock_941 at /lib/../lib64/libpthread.so.0 #2 0x00007f903be6bcdf in pthread_mutex_lock at /lib/../lib64/libpthread.so.0 #3 0x0000564b21456889 in qemu_mutex_lock_impl at ../util/qemu-thread-posix.c:79 #4 0x0000564b213af8a5 in block_job_add_bdrv at ../blockjob.c:224 #5 0x0000564b213b00ad in block_job_create at ../blockjob.c:440 #6 0x0000564b21357c0a in mirror_start_job at ../block/mirror.c:1622 #7 0x0000564b2135a9af in commit_active_start at ../block/mirror.c:1867 #8 0x0000564b2133d132 in qmp_block_commit at ../blockdev.c:2768 #9 0x0000564b2141fef3 in qmp_marshal_block_commit at qapi/qapi-commands-block-core.c:346 #10 0x0000564b214503c9 in do_qmp_dispatch_bh at ../qapi/qmp-dispatch.c:110 #11 0x0000564b21451996 in aio_bh_poll at ../util/async.c:164 #12 0x0000564b2146018e in aio_dispatch at ../util/aio-posix.c:381 #13 0x0000564b2145187e in aio_ctx_dispatch at ../util/async.c:306 #14 0x00007f9040239049 in g_main_context_dispatch at /lib/../lib64/libglib-2.0.so.0 #15 0x0000564b21447368 in main_loop_wait at ../util/main-loop.c:232 #16 0x0000564b21447368 in main_loop_wait at ../util/main-loop.c:255 #17 0x0000564b21447368 in main_loop_wait at ../util/main-loop.c:531 #18 0x0000564b212304e1 in qemu_main_loop at ../softmmu/runstate.c:721 #19 0x0000564b20f7975e in main at ../softmmu/main.c:50 in IO thread when do bdrv_mirror_top_pwritev, the job is NULL, and stop field is false, this means the s object has not been initialized, and this object is initialized by block_job_create(), but the initialize process stuck in acquire the lock. The rootcause is that qemu do release/acquire when hold the lock, at the same time, IO thread get the lock after release stage, and the crash occured. Actually, in this situation, job->job.aio_context will not equal to qemu_get_aio_context(), and will be the same as bs->aio_context, thus, no need to release the lock, becasue bdrv_root_attach_child() will not change the context. This patch fix this issue. Signed-off-by: Michael Qiu --- blockjob.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) -- 2.22.0 diff --git a/blockjob.c b/blockjob.c index c6e20e2f..e1d41db9 100644 --- a/blockjob.c +++ b/blockjob.c @@ -214,12 +214,14 @@ int block_job_add_bdrv(BlockJob *job, const char *name, BlockDriverState *bs, BdrvChild *c; bdrv_ref(bs); - if (job->job.aio_context != qemu_get_aio_context()) { + if (bdrv_get_aio_context(bs) != job->job.aio_context && + job->job.aio_context != qemu_get_aio_context()) { aio_context_release(job->job.aio_context); } c = bdrv_root_attach_child(bs, name, &child_job, job->job.aio_context, perm, shared_perm, job, errp); - if (job->job.aio_context != qemu_get_aio_context()) { + if (bdrv_get_aio_context(bs) != job->job.aio_context && + job->job.aio_context != qemu_get_aio_context()) { aio_context_acquire(job->job.aio_context); } if (c == NULL) {