The bdev layer doesn't call the destruct callback until
all channels have been released, but because the channel
delete callback passes message to the main thread, we can
end up with a complicated race condition. Currently we
have a deferred_free code path to handle this race, but
we can handle this a bit more cleanly by doing the
construct operation on the main_td as well.
This also simplifies the next patch which will
asynchronously destruct the bdev to fix an RPC bug.
Here's the race:
1) first channel was created on thread A, so disk->main_td = thread A
2) second channel was created on thread B
3) first channel is freed (but disk->main_td is still thread A)
4) spdk_bdev_unregister is called on thread C
5) bdev layer gives callback on thread B to upper layer
6) upper layer on thread B frees channel
7) bdev_rbd_destroy_cb runs on thread B and has to send msg to thread A
for processing
8) bdev layer calls bdev_rbd_destruct on thread C (since step #4 was on
thread C)
Signed-off-by: Jim Harris <james.r.harris@intel.com>
Change-Id: I25ede2dc56e24dac0919aed05b9def2560823ee7
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/9158
Community-CI: Broadcom CI <spdk-ci.pdl@broadcom.com>
Community-CI: Mellanox Build Bot
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Ziye Yang <ziye.yang@intel.com>
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