qemu/include/hw/virtio
Sergio Lopez 49b44549ac virtio-blk: On restart, process queued requests in the proper context
On restart, we were scheduling a BH to process queued requests, which
would run before starting up the data plane, leading to those requests
being assigned and started on coroutines on the main context.

This could cause requests to be wrongly processed in parallel from
different threads (the main thread and the iothread managing the data
plane), potentially leading to multiple issues.

For example, stopping and resuming a VM multiple times while the guest
is generating I/O on a virtio_blk device can trigger a crash with a
stack tracing looking like this one:

<------>
 Thread 2 (Thread 0x7ff736765700 (LWP 1062503)):
 #0  0x00005567a13b99d6 in iov_memset
     (iov=0x6563617073206f4e, iov_cnt=1717922848, offset=516096, fillc=0, bytes=7018105756081554803)
     at util/iov.c:69
 #1  0x00005567a13bab73 in qemu_iovec_memset
     (qiov=0x7ff73ec99748, offset=516096, fillc=0, bytes=7018105756081554803) at util/iov.c:530
 #2  0x00005567a12f411c in qemu_laio_process_completion (laiocb=0x7ff6512ee6c0) at block/linux-aio.c:86
 #3  0x00005567a12f42ff in qemu_laio_process_completions (s=0x7ff7182e8420) at block/linux-aio.c:217
 #4  0x00005567a12f480d in ioq_submit (s=0x7ff7182e8420) at block/linux-aio.c:323
 #5  0x00005567a12f43d9 in qemu_laio_process_completions_and_submit (s=0x7ff7182e8420)
     at block/linux-aio.c:236
 #6  0x00005567a12f44c2 in qemu_laio_poll_cb (opaque=0x7ff7182e8430) at block/linux-aio.c:267
 #7  0x00005567a13aed83 in run_poll_handlers_once (ctx=0x5567a2b58c70, timeout=0x7ff7367645f8)
     at util/aio-posix.c:520
 #8  0x00005567a13aee9f in run_poll_handlers (ctx=0x5567a2b58c70, max_ns=16000, timeout=0x7ff7367645f8)
     at util/aio-posix.c:562
 #9  0x00005567a13aefde in try_poll_mode (ctx=0x5567a2b58c70, timeout=0x7ff7367645f8)
     at util/aio-posix.c:597
 #10 0x00005567a13af115 in aio_poll (ctx=0x5567a2b58c70, blocking=true) at util/aio-posix.c:639
 #11 0x00005567a109acca in iothread_run (opaque=0x5567a2b29760) at iothread.c:75
 #12 0x00005567a13b2790 in qemu_thread_start (args=0x5567a2b694c0) at util/qemu-thread-posix.c:519
 #13 0x00007ff73eedf2de in start_thread () at /lib64/libpthread.so.0
 #14 0x00007ff73ec10e83 in clone () at /lib64/libc.so.6

 Thread 1 (Thread 0x7ff743986f00 (LWP 1062500)):
 #0  0x00005567a13b99d6 in iov_memset
     (iov=0x6563617073206f4e, iov_cnt=1717922848, offset=516096, fillc=0, bytes=7018105756081554803)
     at util/iov.c:69
 #1  0x00005567a13bab73 in qemu_iovec_memset
     (qiov=0x7ff73ec99748, offset=516096, fillc=0, bytes=7018105756081554803) at util/iov.c:530
 #2  0x00005567a12f411c in qemu_laio_process_completion (laiocb=0x7ff6512ee6c0) at block/linux-aio.c:86
 #3  0x00005567a12f42ff in qemu_laio_process_completions (s=0x7ff7182e8420) at block/linux-aio.c:217
 #4  0x00005567a12f480d in ioq_submit (s=0x7ff7182e8420) at block/linux-aio.c:323
 #5  0x00005567a12f4a2f in laio_do_submit (fd=19, laiocb=0x7ff5f4ff9ae0, offset=472363008, type=2)
     at block/linux-aio.c:375
 #6  0x00005567a12f4af2 in laio_co_submit
     (bs=0x5567a2b8c460, s=0x7ff7182e8420, fd=19, offset=472363008, qiov=0x7ff5f4ff9ca0, type=2)
     at block/linux-aio.c:394
 #7  0x00005567a12f1803 in raw_co_prw
     (bs=0x5567a2b8c460, offset=472363008, bytes=20480, qiov=0x7ff5f4ff9ca0, type=2)
     at block/file-posix.c:1892
 #8  0x00005567a12f1941 in raw_co_pwritev
     (bs=0x5567a2b8c460, offset=472363008, bytes=20480, qiov=0x7ff5f4ff9ca0, flags=0)
     at block/file-posix.c:1925
 #9  0x00005567a12fe3e1 in bdrv_driver_pwritev
     (bs=0x5567a2b8c460, offset=472363008, bytes=20480, qiov=0x7ff5f4ff9ca0, qiov_offset=0, flags=0)
     at block/io.c:1183
 #10 0x00005567a1300340 in bdrv_aligned_pwritev
     (child=0x5567a2b5b070, req=0x7ff5f4ff9db0, offset=472363008, bytes=20480, align=512, qiov=0x7ff72c0425b8, qiov_offset=0, flags=0) at block/io.c:1980
 #11 0x00005567a1300b29 in bdrv_co_pwritev_part
     (child=0x5567a2b5b070, offset=472363008, bytes=20480, qiov=0x7ff72c0425b8, qiov_offset=0, flags=0)
     at block/io.c:2137
 #12 0x00005567a12baba1 in qcow2_co_pwritev_task
     (bs=0x5567a2b92740, file_cluster_offset=472317952, offset=487305216, bytes=20480, qiov=0x7ff72c0425b8, qiov_offset=0, l2meta=0x0) at block/qcow2.c:2444
 #13 0x00005567a12bacdb in qcow2_co_pwritev_task_entry (task=0x5567a2b48540) at block/qcow2.c:2475
 #14 0x00005567a13167d8 in aio_task_co (opaque=0x5567a2b48540) at block/aio_task.c:45
 #15 0x00005567a13cf00c in coroutine_trampoline (i0=738245600, i1=32759) at util/coroutine-ucontext.c:115
 #16 0x00007ff73eb622e0 in __start_context () at /lib64/libc.so.6
 #17 0x00007ff6626f1350 in  ()
 #18 0x0000000000000000 in  ()
<------>

This is also known to cause crashes with this message (assertion
failed):

 aio_co_schedule: Co-routine was already scheduled in 'aio_co_schedule'

RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1812765
Signed-off-by: Sergio Lopez <slp@redhat.com>
Message-Id: <20200603093240.40489-3-slp@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2020-06-17 14:53:39 +02:00
..
vhost-backend.h vhost-user: add vhost_user_gpu_set_socket() 2019-05-29 06:29:07 +02:00
vhost-scsi-common.h Include hw/qdev-properties.h less 2019-08-16 13:31:53 +02:00
vhost-scsi.h Include hw/qdev-properties.h less 2019-08-16 13:31:53 +02:00
vhost-user-blk.h fix vhost_user_blk_watch crash 2020-03-29 09:52:13 -04:00
vhost-user-fs.h vhost-user-fs: convert to the new virtio_delete_queue function 2020-02-25 08:32:45 -05:00
vhost-user-scsi.h Include hw/qdev-properties.h less 2019-08-16 13:31:53 +02:00
vhost-user-vsock.h virtio: add vhost-user-vsock base device 2020-06-12 10:17:06 -04:00
vhost-user.h Add VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS 2020-06-12 10:17:06 -04:00
vhost-vsock-common.h vhost-vsock: add vhost-vsock-common abstraction 2020-06-12 10:17:06 -04:00
vhost-vsock.h vhost-vsock: add vhost-vsock-common abstraction 2020-06-12 10:17:06 -04:00
vhost.h Include hw/hw.h exactly where needed 2019-08-16 13:31:52 +02:00
virtio-access.h include: Make headers more self-contained 2019-08-16 13:31:51 +02:00
virtio-balloon.h virtio-balloon: Provide an interface for free page reporting 2020-06-09 14:18:04 -04:00
virtio-blk.h virtio-blk: On restart, process queued requests in the proper context 2020-06-17 14:53:39 +02:00
virtio-bus.h Clean up inclusion of sysemu/sysemu.h 2019-08-16 13:31:53 +02:00
virtio-crypto.h Clean up ill-advised or unusual header guards 2019-05-13 08:58:55 +02:00
virtio-gpu-bswap.h include: Make headers more self-contained 2019-08-16 13:31:51 +02:00
virtio-gpu-pci.h hw/display: add vhost-user-vga & gpu-pci 2019-05-29 06:30:45 +02:00
virtio-gpu-pixman.h virtio-gpu: add a pixman helper header 2019-05-29 06:29:07 +02:00
virtio-gpu.h edid: flip the default to enabled 2019-06-13 09:34:50 +02:00
virtio-input.h Add vhost-user-input-pci 2019-05-10 14:52:47 +02:00
virtio-iommu.h misc: Replace zero-length arrays with flexible array member (automatic) 2020-03-16 22:07:42 +01:00
virtio-mmio.h hw/virtio: Factorize virtio-mmio headers 2019-10-22 09:38:42 +02:00
virtio-net.h net/virtio: add failover support 2019-10-29 18:55:26 -04:00
virtio-pmem.h Include sysemu/hostmem.h less 2019-08-16 13:31:53 +02:00
virtio-rng.h virtio-rng: Keep the default backend out of VirtIORNGConf 2019-09-04 06:32:51 -04:00
virtio-scsi.h virtio: make seg_max virtqueue size dependent 2020-01-06 12:04:43 -05:00
virtio-serial.h Include hw/qdev-properties.h less 2019-08-16 13:31:53 +02:00
virtio.h virtio: don't enable notifications during polling 2020-01-05 07:03:03 -05:00