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qemu-img: Take graph lock more selectively 

If we take a reader lock, we can't call any functions that take a writer
lock internally without causing deadlocks once the reader lock is
actually enforced in the main thread, too. Take the reader lock only
where it is actually needed.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20230510203601.418015-5-kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2023-05-10 22:35:57 +02:00
parent e3e31dc872
commit 3db0c8b25c
1 changed files with 3 additions and 2 deletions
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5
qemu-img.c
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@ -2938,8 +2938,6 @@ static BlockGraphInfoList *collect_image_info_list(bool image_opts,
} }
bs = blk_bs(blk); bs = blk_bs(blk);
GRAPH_RDLOCK_GUARD_MAINLOOP();
/* /*
* Note that the returned BlockGraphInfo object will not have * Note that the returned BlockGraphInfo object will not have
* information about this image's backing node, because we have opened * information about this image's backing node, because we have opened
@ -2947,7 +2945,10 @@ static BlockGraphInfoList *collect_image_info_list(bool image_opts,
* duplicate the backing chain information that we obtain by walking * duplicate the backing chain information that we obtain by walking
* the chain manually here. * the chain manually here.
*/ */
bdrv_graph_rdlock_main_loop();
bdrv_query_block_graph_info(bs, &info, &err); bdrv_query_block_graph_info(bs, &info, &err);
bdrv_graph_rdunlock_main_loop();
if (err) { if (err) {
error_report_err(err); error_report_err(err);
blk_unref(blk); blk_unref(blk);