mirror of
https://gitlab.com/qemu-project/qemu
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8f5e9a8ee1
Each vhost-user-blk request runs in a coroutine. When the BlockBackend enters a drained section we need to enter a quiescent state. Currently any in-flight requests race with bdrv_drained_begin() because it is unaware of vhost-user-blk requests. When blk_co_preadv/pwritev()/etc returns it wakes the bdrv_drained_begin() thread but vhost-user-blk request processing has not yet finished. The request coroutine continues executing while the main loop thread thinks it is in a drained section. One example where this is unsafe is for blk_set_aio_context() where bdrv_drained_begin() is called before .aio_context_detached() and .aio_context_attach(). If request coroutines are still running after bdrv_drained_begin(), then the AioContext could change underneath them and they race with new requests processed in the new AioContext. This could lead to virtqueue corruption, for example. (This example is theoretical, I came across this while reading the code and have not tried to reproduce it.) It's easy to make bdrv_drained_begin() wait for in-flight requests: add a .drained_poll() callback that checks the VuServer's in-flight counter. VuServer just needs an API that returns true when there are requests in flight. The in-flight counter needs to be atomic. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Message-Id: <20230516190238.8401-7-stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com> |
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| .. | ||
| aio-posix.c | ||
| aio-posix.h | ||
| aio-wait.c | ||
| aio-win32.c | ||
| aiocb.c | ||
| async-teardown.c | ||
| async.c | ||
| atomic64.c | ||
| base64.c | ||
| bitmap.c | ||
| bitops.c | ||
| block-helpers.c | ||
| block-helpers.h | ||
| buffer.c | ||
| bufferiszero.c | ||
| cacheflush.c | ||
| compatfd.c | ||
| coroutine-sigaltstack.c | ||
| coroutine-ucontext.c | ||
| coroutine-windows.c | ||
| cpuinfo-aarch64.c | ||
| cpuinfo-i386.c | ||
| crc-ccitt.c | ||
| crc32c.c | ||
| cutils.c | ||
| dbus.c | ||
| drm.c | ||
| envlist.c | ||
| error-report.c | ||
| error.c | ||
| event_notifier-posix.c | ||
| event_notifier-win32.c | ||
| fdmon-epoll.c | ||
| fdmon-io_uring.c | ||
| fdmon-poll.c | ||
| fifo8.c | ||
| filemonitor-inotify.c | ||
| filemonitor-stub.c | ||
| getauxval.c | ||
| guest-random.c | ||
| hbitmap.c | ||
| hexdump.c | ||
| host-utils.c | ||
| id.c | ||
| int128.c | ||
| interval-tree.c | ||
| iov.c | ||
| iova-tree.c | ||
| keyval.c | ||
| lockcnt.c | ||
| log.c | ||
| main-loop.c | ||
| memalign.c | ||
| memfd.c | ||
| meson.build | ||
| mmap-alloc.c | ||
| module.c | ||
| notify.c | ||
| nvdimm-utils.c | ||
| osdep.c | ||
| oslib-posix.c | ||
| oslib-win32.c | ||
| path.c | ||
| qdist.c | ||
| qemu-co-shared-resource.c | ||
| qemu-co-timeout.c | ||
| qemu-config.c | ||
| qemu-coroutine-io.c | ||
| qemu-coroutine-lock.c | ||
| qemu-coroutine-sleep.c | ||
| qemu-coroutine.c | ||
| qemu-option.c | ||
| qemu-print.c | ||
| qemu-progress.c | ||
| qemu-sockets.c | ||
| qemu-thread-common.h | ||
| qemu-thread-posix.c | ||
| qemu-thread-win32.c | ||
| qemu-timer-common.c | ||
| qemu-timer.c | ||
| qht.c | ||
| qsp.c | ||
| qtree.c | ||
| range.c | ||
| rcu.c | ||
| readline.c | ||
| selfmap.c | ||
| stats64.c | ||
| sys_membarrier.c | ||
| systemd.c | ||
| thread-context.c | ||
| thread-pool.c | ||
| throttle.c | ||
| timed-average.c | ||
| trace-events | ||
| trace.h | ||
| transactions.c | ||
| unicode.c | ||
| uri.c | ||
| userfaultfd.c | ||
| uuid.c | ||
| vfio-helpers.c | ||
| vhost-user-server.c | ||
| yank.c | ||