[PULL,12/13] vl: Drain before (block) job cancel when quitting
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Message ID 20190719134345.23526-13-kwolf@redhat.com
State New
Headers show
Series
  • [PULL,01/13] iotests: Set read-zeroes on in null block driver for Valgrind
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Commit Message

Kevin Wolf July 19, 2019, 1:43 p.m. UTC
From: Max Reitz <mreitz@redhat.com>

If the main loop cancels all block jobs while the block layer is not
drained, this cancelling may not happen instantaneously.  We can start a
drained section before vm_shutdown(), which entails another
bdrv_drain_all(); this nested bdrv_drain_all() will thus be a no-op,
basically.

We do not have to end the drained section, because we actually do not
want any requests to happen from this point on.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 vl.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

Patch
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diff --git a/vl.c b/vl.c
index a5808f9a02..53335a5470 100644
--- a/vl.c
+++ b/vl.c
@@ -4480,6 +4480,17 @@  int main(int argc, char **argv, char **envp)
      */
     migration_shutdown();
 
+    /*
+     * We must cancel all block jobs while the block layer is drained,
+     * or cancelling will be affected by throttling and thus may block
+     * for an extended period of time.
+     * vm_shutdown() will bdrv_drain_all(), so we may as well include
+     * it in the drained section.
+     * We do not need to end this section, because we do not want any
+     * requests happening from here on anyway.
+     */
+    bdrv_drain_all_begin();
+
     /* No more vcpu or device emulation activity beyond this point */
     vm_shutdown();