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nfsd: Simplify code around svc_exit_thread() call in nfsd()

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[ Upstream commit 18e4cf9155 ]

Previously a thread could exit asynchronously (due to a signal) so some
care was needed to hold nfsd_mutex over the last svc_put() call.  Now a
thread can only exit when svc_set_num_threads() is called, and this is
always called under nfsd_mutex.  So no care is needed.

Not only is the mutex held when a thread exits now, but the svc refcount
is elevated, so the svc_put() in svc_exit_thread() will never be a final
put, so the mutex isn't even needed at this point in the code.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
NeilBrown 2024-08-26 11:06:57 -04:00 committed by Greg Kroah-Hartman
parent a3754e840e
commit 8862e33951
2 changed files with 0 additions and 36 deletions
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23
fs/nfsd/nfssvc.c
View File

@ -983,31 +983,8 @@ nfsd(void *vrqstp)
atomic_dec(&nfsd_th_cnt);
out:
/* Take an extra ref so that the svc_put in svc_exit_thread()
* doesn't call svc_destroy()
*/
svc_get(nn->nfsd_serv);
/* Release the thread */
svc_exit_thread(rqstp);
/* We need to drop a ref, but may not drop the last reference
* without holding nfsd_mutex, and we cannot wait for nfsd_mutex as that
* could deadlock with nfsd_shutdown_threads() waiting for us.
* So three options are:
* - drop a non-final reference,
* - get the mutex without waiting
* - sleep briefly andd try the above again
*/
while (!svc_put_not_last(nn->nfsd_serv)) {
if (mutex_trylock(&nfsd_mutex)) {
nfsd_put(net);
mutex_unlock(&nfsd_mutex);
break;
}
msleep(20);
}
return 0;
}

13
include/linux/sunrpc/svc.h
View File

@ -123,19 +123,6 @@ static inline void svc_put(struct svc_serv *serv)
kref_put(&serv->sv_refcnt, svc_destroy);
}
/**
* svc_put_not_last - decrement non-final reference count on SUNRPC serv
* @serv: the svc_serv to have count decremented
*
* Returns: %true is refcount was decremented.
*
* If the refcount is 1, it is not decremented and instead failure is reported.
*/
static inline bool svc_put_not_last(struct svc_serv *serv)
{
return refcount_dec_not_one(&serv->sv_refcnt.refcount);
}
/*
* Maximum payload size supported by a kernel RPC server.
* This is use to determine the max number of pages nfsd is