If an svc thread needs to perform some initialisation that might fail,
it has no good way to handle the failure.
Before the thread can exit it must call svc_exit_thread(), but that
requires the service mutex to be held. The thread cannot simply take
the mutex as that could deadlock if there is a concurrent attempt to
shut down all threads (which is unlikely, but not impossible).
nfsd currently call svc_exit_thread() unprotected in the unlikely event
that unshare_fs_struct() fails.
We can clean this up by introducing svc_thread_init_status() by which an
svc thread can report whether initialisation has succeeded. If it has,
it continues normally into the action loop. If it has not,
svc_thread_init_status() immediately aborts the thread.
svc_start_kthread() waits for either of these to happen, and calls
svc_exit_thread() (under the mutex) if the thread aborted.
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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