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authorMichael Qiu <qiudayu@huayun.com>2021-02-03 10:40:59 +0800
committerKevin Wolf <kwolf@redhat.com>2021-02-15 15:10:14 +0100
commit076d467aacdf6dc5d01e2e61740b1795f2aec2f6 (patch)
treefd9ec57c3e0413828b1e0862d155d3093f3f0384 /.gitignore
parentb34cdf32256e59e0183fe0f7ee5b5f4865d9ccc0 (diff)
blockjob: Fix crash with IOthread when block commit after snapshot
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 <qiudayu@huayun.com> Message-Id: <20210203024059.52683-1-08005325@163.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to '.gitignore')
0 files changed, 0 insertions, 0 deletions