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authorPaolo Bonzini <pbonzini@redhat.com>2016-10-27 12:49:05 +0200
committerFam Zheng <famz@redhat.com>2016-10-28 21:50:18 +0800
commitc9d1a56174339b0afdef63b7d151b38f4bb6dae5 (patch)
tree1eb8359be422f1abbf98c5781cee063163861f67 /include/block/block_int.h
parent9e944cb4744b527dd93aa989023739375a8880fb (diff)
block: only call aio_poll on the current thread's AioContext
aio_poll is not thread safe; for example bdrv_drain can hang if the last in-flight I/O operation is completed in the I/O thread after the main thread has checked bs->in_flight. The bug remains latent as long as all of it is called within aio_context_acquire/aio_context_release, but this will change soon. To fix this, if bdrv_drain is called from outside the I/O thread, signal the main AioContext through a dummy bottom half. The event loop then only runs in the I/O thread. Reviewed-by: Fam Zheng <famz@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <1477565348-5458-18-git-send-email-pbonzini@redhat.com> Signed-off-by: Fam Zheng <famz@redhat.com>
Diffstat (limited to 'include/block/block_int.h')
-rw-r--r--include/block/block_int.h17
1 files changed, 17 insertions, 0 deletions
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 1044dfef43..e7ff58419c 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -475,6 +475,8 @@ struct BlockDriverState {
unsigned int in_flight;
unsigned int serialising_in_flight;
+ bool wakeup;
+
/* Offset after the highest byte written to */
uint64_t wr_highest_offset;
@@ -633,6 +635,21 @@ void bdrv_remove_aio_context_notifier(BlockDriverState *bs,
void (*aio_context_detached)(void *),
void *opaque);
+/**
+ * bdrv_wakeup:
+ * @bs: The BlockDriverState for which an I/O operation has been completed.
+ *
+ * Wake up the main thread if it is waiting on BDRV_POLL_WHILE. During
+ * synchronous I/O on a BlockDriverState that is attached to another
+ * I/O thread, the main thread lets the I/O thread's event loop run,
+ * waiting for the I/O operation to complete. A bdrv_wakeup will wake
+ * up the main thread if necessary.
+ *
+ * Manual calls to bdrv_wakeup are rarely necessary, because
+ * bdrv_dec_in_flight already calls it.
+ */
+void bdrv_wakeup(BlockDriverState *bs);
+
#ifdef _WIN32
int is_windows_drive(const char *filename);
#endif