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authorNeilBrown <neilb@suse.de>2021-11-29 15:51:25 +1100
committerChuck Lever <chuck.lever@oracle.com>2021-12-13 13:42:52 -0500
commit2a36395fac3b72771f87c3ee4387e3a96d85a7cc (patch)
treeb2078229902140dbe1ffa20383eb730a5e7ddef0
parent9b6c8c9bebccd5fb785c306b948c08874a88874d (diff)
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SUNRPC: use sv_lock to protect updates to sv_nrthreads.
Using sv_lock means we don't need to hold the service mutex over these updates. In particular, svc_exit_thread() no longer requires synchronisation, so threads can exit asynchronously. Note that we could use an atomic_t, but as there are many more read sites than writes, that would add unnecessary noise to the code. Some reads are already racy, and there is no need for them to not be. Signed-off-by: NeilBrown <neilb@suse.de> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
-rw-r--r--fs/nfsd/nfssvc.c5
-rw-r--r--net/sunrpc/svc.c9
2 files changed, 9 insertions, 5 deletions
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index fc5899502a83..e9c9fa820b17 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -55,9 +55,8 @@ static __be32 nfsd_init_request(struct svc_rqst *,
struct svc_process_info *);
/*
- * nfsd_mutex protects nn->nfsd_serv -- both the pointer itself and the members
- * of the svc_serv struct. In particular, ->sv_nrthreads but also to some
- * extent ->sv_temp_socks and ->sv_permsocks.
+ * nfsd_mutex protects nn->nfsd_serv -- both the pointer itself and some members
+ * of the svc_serv struct such as ->sv_temp_socks and ->sv_permsocks.
*
* If (out side the lock) nn->nfsd_serv is non-NULL, then it must point to a
* properly initialised 'struct svc_serv' with ->sv_nrthreads > 0 (unless
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index acddc6e12e9e..2b2042234e4b 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -523,7 +523,7 @@ EXPORT_SYMBOL_GPL(svc_shutdown_net);
/*
* Destroy an RPC service. Should be called with appropriate locking to
- * protect the sv_nrthreads, sv_permsocks and sv_tempsocks.
+ * protect sv_permsocks and sv_tempsocks.
*/
void
svc_destroy(struct kref *ref)
@@ -639,7 +639,10 @@ svc_prepare_thread(struct svc_serv *serv, struct svc_pool *pool, int node)
return ERR_PTR(-ENOMEM);
svc_get(serv);
- serv->sv_nrthreads++;
+ spin_lock_bh(&serv->sv_lock);
+ serv->sv_nrthreads += 1;
+ spin_unlock_bh(&serv->sv_lock);
+
spin_lock_bh(&pool->sp_lock);
pool->sp_nrthreads++;
list_add_rcu(&rqstp->rq_all, &pool->sp_all_threads);
@@ -880,7 +883,9 @@ svc_exit_thread(struct svc_rqst *rqstp)
list_del_rcu(&rqstp->rq_all);
spin_unlock_bh(&pool->sp_lock);
+ spin_lock_bh(&serv->sv_lock);
serv->sv_nrthreads -= 1;
+ spin_unlock_bh(&serv->sv_lock);
svc_sock_update_bufs(serv);
svc_rqst_free(rqstp);