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authorStefan Hajnoczi <stefanha@redhat.com>2023-03-07 16:04:26 -0500
committerKevin Wolf <kwolf@redhat.com>2023-04-25 13:15:21 +0200
commitef80ec5067d7ca5b46e5b88be1be33cddfd33551 (patch)
treee34b78dcb1dbdad2cdf7618ab3ac03670d838128
parentc4d5bf99b7fccf8849316b9f5100525b1beb8237 (diff)
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block: make BlockBackend->disable_request_queuing atomic
This field is accessed by multiple threads without a lock. Use explicit qatomic_read()/qatomic_set() calls. There is no need for acquire/release because blk_set_disable_request_queuing() doesn't provide any guarantees (it helps that it's used at BlockBackend creation time and not when there is I/O in flight). Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Hanna Czenczek <hreitz@redhat.com> Message-Id: <20230307210427.269214-3-stefanha@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
-rw-r--r--block/block-backend.c7
1 files changed, 4 insertions, 3 deletions
diff --git a/block/block-backend.c b/block/block-backend.c
index 2ae768f..8552b6d 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -82,7 +82,7 @@ struct BlockBackend {
int quiesce_counter; /* atomic: written under BQL, read by other threads */
CoQueue queued_requests;
- bool disable_request_queuing;
+ bool disable_request_queuing; /* atomic */
VMChangeStateEntry *vmsh;
bool force_allow_inactivate;
@@ -1232,7 +1232,7 @@ void blk_set_allow_aio_context_change(BlockBackend *blk, bool allow)
void blk_set_disable_request_queuing(BlockBackend *blk, bool disable)
{
IO_CODE();
- blk->disable_request_queuing = disable;
+ qatomic_set(&blk->disable_request_queuing, disable);
}
static int coroutine_fn GRAPH_RDLOCK
@@ -1271,7 +1271,8 @@ static void coroutine_fn blk_wait_while_drained(BlockBackend *blk)
{
assert(blk->in_flight > 0);
- if (qatomic_read(&blk->quiesce_counter) && !blk->disable_request_queuing) {
+ if (qatomic_read(&blk->quiesce_counter) &&
+ !qatomic_read(&blk->disable_request_queuing)) {
blk_dec_in_flight(blk);
qemu_co_queue_wait(&blk->queued_requests, NULL);
blk_inc_in_flight(blk);