From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 623CEC433DB for ; Mon, 15 Feb 2021 15:12:16 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D17FB64D7F for ; Mon, 15 Feb 2021 15:12:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D17FB64D7F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:60466 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lBfXq-0007w3-Ou for qemu-devel@archiver.kernel.org; Mon, 15 Feb 2021 10:12:14 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:55172) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lBfNN-0005fR-4O for qemu-devel@nongnu.org; Mon, 15 Feb 2021 10:01:25 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:36927) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1lBfNL-0000nU-4z for qemu-devel@nongnu.org; Mon, 15 Feb 2021 10:01:24 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613401282; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=gB2c914N453Rav2bP3tPhX9RRzLXU/YZJW0xtRFFYbI=; b=cE9FDdK5ZcwC+gOYealvovzlJ2gsy0+UIiWEO2ZS+PeV3z92vQBevwVGRHPX9i3vZgqWbT o2bjTi+b2rrfrMkqoMWRlwfDyp09kcH5Ah6ayqA/KkWV7l5XVEEW/rKiIEfhzehnvcZLvX YSANOL/oyPDBX+1jh0wFR4wCLPeYMvw= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-100-8E9Cek4wMKyzhyaqRnlLwg-1; Mon, 15 Feb 2021 10:01:08 -0500 X-MC-Unique: 8E9Cek4wMKyzhyaqRnlLwg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id BEB16801975; Mon, 15 Feb 2021 15:01:07 +0000 (UTC) Received: from merkur.fritz.box (ovpn-113-28.ams2.redhat.com [10.36.113.28]) by smtp.corp.redhat.com (Postfix) with ESMTP id C747C5C241; Mon, 15 Feb 2021 15:01:06 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Subject: [PULL 03/11] blockjob: Fix crash with IOthread when block commit after snapshot Date: Mon, 15 Feb 2021 16:00:52 +0100 Message-Id: <20210215150100.436555-4-kwolf@redhat.com> In-Reply-To: <20210215150100.436555-1-kwolf@redhat.com> References: <20210215150100.436555-1-kwolf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset="US-ASCII" Received-SPF: pass client-ip=63.128.21.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=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: kwolf@redhat.com, peter.maydell@linaro.org, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: Michael Qiu 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 Call trace of IO thread: 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 ... 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 MirrorBDSOpaque "s" object has not been initialized yet, and this object is initialized by block_job_create(), but the initialize process is stuck in acquiring the lock. In this situation, IO thread come to bdrv_mirror_top_pwritev(),which means that mirror-top node is already inserted into block graph, but its bs->opaque->job is not initialized. The root cause is that qemu main thread 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. Fixes: 132ada80 "block: Adjust AioContexts when attaching nodes" Signed-off-by: Michael Qiu Message-Id: <20210203024059.52683-1-08005325@163.com> Signed-off-by: Kevin Wolf --- blockjob.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/blockjob.c b/blockjob.c index db3a21699c..f2feff051d 100644 --- a/blockjob.c +++ b/blockjob.c @@ -212,15 +212,19 @@ int block_job_add_bdrv(BlockJob *job, const char *name, BlockDriverState *bs, uint64_t perm, uint64_t shared_perm, Error **errp) { BdrvChild *c; + bool need_context_ops; bdrv_ref(bs); - if (job->job.aio_context != qemu_get_aio_context()) { + + need_context_ops = bdrv_get_aio_context(bs) != job->job.aio_context; + + if (need_context_ops && job->job.aio_context != qemu_get_aio_context()) { aio_context_release(job->job.aio_context); } c = bdrv_root_attach_child(bs, name, &child_job, 0, job->job.aio_context, perm, shared_perm, job, errp); - if (job->job.aio_context != qemu_get_aio_context()) { + if (need_context_ops && job->job.aio_context != qemu_get_aio_context()) { aio_context_acquire(job->job.aio_context); } if (c == NULL) { -- 2.29.2