mirror of https://github.com/xemu-project/xemu.git
c8bf923d5e
This patch fixes a race condition in test-bdrv-drain that is difficult to reproduce. test-bdrv-drain sometimes fails without an error message on the block pull request sent by Kevin Wolf on Sep 4, 2023. I was able to reproduce it locally and found that "block-backend: process I/O in the current AioContext" (in this patch series) is the first commit where it reproduces. I do not know why "block-backend: process I/O in the current AioContext" exposes this bug. It might be related to the fact that the test's preadv request runs in the main thread instead of IOThread a after my commit. That might simply change the timing of the test. Now on to the race condition in test-bdrv-drain. The main thread schedules a BH in IOThread a and then drains the BDS: aio_bh_schedule_oneshot(ctx_a, test_iothread_main_thread_bh, &data); /* The request is running on the IOThread a. Draining its block device * will make sure that it has completed as far as the BDS is concerned, * but the drain in this thread can continue immediately after * bdrv_dec_in_flight() and aio_ret might be assigned only slightly * later. */ do_drain_begin(drain_type, bs); If the BH completes before do_drain_begin() then there is nothing to worry about. If the BH invokes bdrv_flush() before do_drain_begin(), then do_drain_begin() waits for it to complete. The problematic case is when do_drain_begin() runs before the BH enters bdrv_flush(). Then do_drain_begin() misses the BH and the drain mechanism has failed in quiescing I/O. Fix this by incrementing the in_flight counter so that do_drain_begin() waits for test_iothread_main_thread_bh(). Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Message-ID: <20230912231037.826804-3-stefanha@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com> |
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| avocado | ||
| bench | ||
| data | ||
| decode | ||
| docker | ||
| fp | ||
| guest-debug | ||
| image-fuzzer | ||
| include | ||
| keys | ||
| lcitool | ||
| migration | ||
| multiboot | ||
| perf/block/qcow2 | ||
| plugin | ||
| qapi-schema | ||
| qemu-iotests | ||
| qtest | ||
| rocker | ||
| tcg | ||
| tsan | ||
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| unit | ||
| vm | ||
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| Makefile.include | ||
| dbus-vmstate-daemon.sh | ||
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| test-qht-par.c | ||
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