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authorVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>2021-07-03 00:16:36 +0300
committerKevin Wolf <kwolf@redhat.com>2021-07-20 13:14:45 +0200
commitd44dae1a7cf782ec9235746ebb0e6c1a20dd7288 (patch)
treeca473538c698f1375c84a3eb9968f9d0d6eb508e /block
parente0f69d83d5c5c039b133b60b5a7130dedeeaca42 (diff)
block/mirror: fix active mirror dead-lock in mirror_wait_on_conflicts
It's possible that requests start to wait each other in mirror_wait_on_conflicts(). To avoid it let's use same technique as in block/io.c in bdrv_wait_serialising_requests_locked() / bdrv_find_conflicting_request(): don't wait on intersecting request if it is already waiting for some other request. For details of the dead-lock look at testIntersectingActiveIO() test-case which we actually fixing now. Fixes: d06107ade0ce74dc39739bac80de84b51ec18546 Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Message-Id: <20210702211636.228981-4-vsementsov@virtuozzo.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block')
-rw-r--r--block/mirror.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/block/mirror.c b/block/mirror.c
index ad6aac2f95..98fc66eabf 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -107,6 +107,7 @@ struct MirrorOp {
bool is_in_flight;
CoQueue waiting_requests;
Coroutine *co;
+ MirrorOp *waiting_for_op;
QTAILQ_ENTRY(MirrorOp) next;
};
@@ -159,7 +160,18 @@ static void coroutine_fn mirror_wait_on_conflicts(MirrorOp *self,
if (ranges_overlap(self_start_chunk, self_nb_chunks,
op_start_chunk, op_nb_chunks))
{
+ /*
+ * If the operation is already (indirectly) waiting for us, or
+ * will wait for us as soon as it wakes up, then just go on
+ * (instead of producing a deadlock in the former case).
+ */
+ if (op->waiting_for_op) {
+ continue;
+ }
+
+ self->waiting_for_op = op;
qemu_co_queue_wait(&op->waiting_requests, NULL);
+ self->waiting_for_op = NULL;
break;
}
}