Commit 2e8fc923 authored by NeilBrown's avatar NeilBrown Committed by Chuck Lever
Browse files

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: default avatarNeilBrown <neilb@suse.de>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
parent 9a0e6acc

fs/nfsd/nfssvc.c

+5 −6
Original line number Diff line number Diff line
@@ -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;

}

include/linux/sunrpc/svc.h

+1 −1
Original line number Diff line number Diff line
@@ -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 */

net/sunrpc/svc.c

+20 −17
Original line number Diff line number Diff line
@@ -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);

	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);