From 2e8fc923fe476db8cab9b6458027eccb22f3b6e6 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 11 Sep 2023 10:40:09 -0400 Subject: [PATCH] SUNRPC: change sp_nrthreads to atomic_t Using an atomic_t avoids the need to take a spinlock (which can soon be removed). Choosing a thread to kill needs to be careful as we cannot set the "die now" bit atomically with the test on the count. Instead we temporarily increase the count. Signed-off-by: NeilBrown Signed-off-by: Chuck Lever --- fs/nfsd/nfssvc.c | 11 +++++------ include/linux/sunrpc/svc.h | 2 +- net/sunrpc/svc.c | 37 ++++++++++++++++++++----------------- 3 files changed, 26 insertions(+), 24 deletions(-) diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c index 0b03a2e50dee..433154b9eee0 100644 --- a/fs/nfsd/nfssvc.c +++ b/fs/nfsd/nfssvc.c @@ -713,14 +713,13 @@ int nfsd_nrpools(struct net *net) int nfsd_get_nrthreads(int n, int *nthreads, struct net *net) { - int i = 0; struct nfsd_net *nn = net_generic(net, nfsd_net_id); + struct svc_serv *serv = nn->nfsd_serv; + int i; - if (nn->nfsd_serv != NULL) { - for (i = 0; i < nn->nfsd_serv->sv_nrpools && i < n; i++) - nthreads[i] = nn->nfsd_serv->sv_pools[i].sp_nrthreads; - } - + if (serv) + for (i = 0; i < serv->sv_nrpools && i < n; i++) + nthreads[i] = atomic_read(&serv->sv_pools[i].sp_nrthreads); return 0; } diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h index 7ff9fe785e49..9d0fcd6148ae 100644 --- a/include/linux/sunrpc/svc.h +++ b/include/linux/sunrpc/svc.h @@ -36,7 +36,7 @@ struct svc_pool { unsigned int sp_id; /* pool id; also node id on NUMA */ spinlock_t sp_lock; /* protects all fields */ struct lwq sp_xprts; /* pending transports */ - unsigned int sp_nrthreads; /* # of threads in pool */ + atomic_t sp_nrthreads; /* # of threads in pool */ struct list_head sp_all_threads; /* all server threads */ struct llist_head sp_idle_threads; /* idle server threads */ diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c index 244b5b9eba4d..0928d3f918b0 100644 --- a/net/sunrpc/svc.c +++ b/net/sunrpc/svc.c @@ -681,8 +681,8 @@ svc_prepare_thread(struct svc_serv *serv, struct svc_pool *pool, int node) serv->sv_nrthreads += 1; spin_unlock_bh(&serv->sv_lock); + atomic_inc(&pool->sp_nrthreads); spin_lock_bh(&pool->sp_lock); - pool->sp_nrthreads++; list_add_rcu(&rqstp->rq_all, &pool->sp_all_threads); spin_unlock_bh(&pool->sp_lock); return rqstp; @@ -727,23 +727,24 @@ svc_pool_next(struct svc_serv *serv, struct svc_pool *pool, unsigned int *state) } static struct svc_pool * -svc_pool_victim(struct svc_serv *serv, struct svc_pool *pool, unsigned int *state) +svc_pool_victim(struct svc_serv *serv, struct svc_pool *target_pool, + unsigned int *state) { + struct svc_pool *pool; unsigned int i; +retry: + pool = target_pool; + if (pool != NULL) { - spin_lock_bh(&pool->sp_lock); - if (pool->sp_nrthreads) + if (atomic_inc_not_zero(&pool->sp_nrthreads)) goto found_pool; - spin_unlock_bh(&pool->sp_lock); return NULL; } else { for (i = 0; i < serv->sv_nrpools; i++) { pool = &serv->sv_pools[--(*state) % serv->sv_nrpools]; - spin_lock_bh(&pool->sp_lock); - if (pool->sp_nrthreads) + if (atomic_inc_not_zero(&pool->sp_nrthreads)) goto found_pool; - spin_unlock_bh(&pool->sp_lock); } return NULL; } @@ -751,8 +752,12 @@ svc_pool_victim(struct svc_serv *serv, struct svc_pool *pool, unsigned int *stat found_pool: set_bit(SP_VICTIM_REMAINS, &pool->sp_flags); set_bit(SP_NEED_VICTIM, &pool->sp_flags); - spin_unlock_bh(&pool->sp_lock); - return pool; + if (!atomic_dec_and_test(&pool->sp_nrthreads)) + return pool; + /* Nothing left in this pool any more */ + clear_bit(SP_NEED_VICTIM, &pool->sp_flags); + clear_bit(SP_VICTIM_REMAINS, &pool->sp_flags); + goto retry; } static int @@ -828,13 +833,10 @@ svc_stop_kthreads(struct svc_serv *serv, struct svc_pool *pool, int nrservs) int svc_set_num_threads(struct svc_serv *serv, struct svc_pool *pool, int nrservs) { - if (pool == NULL) { + if (!pool) nrservs -= serv->sv_nrthreads; - } else { - spin_lock_bh(&pool->sp_lock); - nrservs -= pool->sp_nrthreads; - spin_unlock_bh(&pool->sp_lock); - } + else + nrservs -= atomic_read(&pool->sp_nrthreads); if (nrservs > 0) return svc_start_kthreads(serv, pool, nrservs); @@ -921,10 +923,11 @@ svc_exit_thread(struct svc_rqst *rqstp) struct svc_pool *pool = rqstp->rq_pool; spin_lock_bh(&pool->sp_lock); - pool->sp_nrthreads--; list_del_rcu(&rqstp->rq_all); spin_unlock_bh(&pool->sp_lock); + atomic_dec(&pool->sp_nrthreads); + spin_lock_bh(&serv->sv_lock); serv->sv_nrthreads -= 1; spin_unlock_bh(&serv->sv_lock);