From: NeilBrown <neilb@xxxxxxx>
svc threads are currently stopped using kthread_stop(). This requires
identifying a specific thread. However we don't care which thread
stops, just as long as one does.
So instead, set a flag in the svc_pool to say that a thread needs to
die, and have each thread check this flag instead of calling
kthread_should_stop(). The first thread to find and clear this flag
then moves towards exiting.
This removes an explicit dependency on sp_all_threads which will make a
future patch simpler.
Signed-off-by: NeilBrown <neilb@xxxxxxx>
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
fs/lockd/svc.c | 5 ++---
fs/lockd/svclock.c | 5 ++---
fs/nfs/callback.c | 2 +-
fs/nfsd/nfs4proc.c | 8 +++++---
fs/nfsd/nfssvc.c | 2 +-
include/linux/lockd/lockd.h | 2 +-
include/linux/sunrpc/svc.h | 26 +++++++++++++++++++++++++-
net/sunrpc/svc.c | 43 +++++++++++++++++++++----------------------
net/sunrpc/svc_xprt.c | 7 +++----
9 files changed, 61 insertions(+), 39 deletions(-)
diff --git a/fs/lockd/svc.c b/fs/lockd/svc.c
index 6579948070a4..b441c706c2b8 100644
--- a/fs/lockd/svc.c
+++ b/fs/lockd/svc.c
@@ -24,7 +24,6 @@
#include <linux/uio.h>
#include <linux/smp.h>
#include <linux/mutex.h>
-#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/inetdevice.h>
@@ -135,11 +134,11 @@ lockd(void *vrqstp)
* The main request loop. We don't terminate until the last
* NFS mount or NFS daemon has gone away.
*/
- while (!kthread_should_stop()) {
+ while (!svc_thread_should_stop(rqstp)) {
/* update sv_maxconn if it has changed */
rqstp->rq_server->sv_maxconn = nlm_max_connections;
- nlmsvc_retry_blocked();
+ nlmsvc_retry_blocked(rqstp);
svc_recv(rqstp);
}
if (nlmsvc_ops)
diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c
index 43aeba9de55c..5fea06555f42 100644
--- a/fs/lockd/svclock.c
+++ b/fs/lockd/svclock.c
@@ -30,7 +30,6 @@
#include <linux/sunrpc/svc_xprt.h>
#include <linux/lockd/nlm.h>
#include <linux/lockd/lockd.h>
-#include <linux/kthread.h>
#include <linux/exportfs.h>
#define NLMDBG_FACILITY NLMDBG_SVCLOCK
@@ -1020,13 +1019,13 @@ retry_deferred_block(struct nlm_block *block)
* be retransmitted.
*/
void
-nlmsvc_retry_blocked(void)
+nlmsvc_retry_blocked(struct svc_rqst *rqstp)
{
unsigned long timeout = MAX_SCHEDULE_TIMEOUT;
struct nlm_block *block;
spin_lock(&nlm_blocked_lock);
- while (!list_empty(&nlm_blocked) && !kthread_should_stop()) {
+ while (!list_empty(&nlm_blocked) && !svc_thread_should_stop(rqstp)) {
block = list_entry(nlm_blocked.next, struct nlm_block, b_list);
if (block->b_when == NLM_NEVER)
diff --git a/fs/nfs/callback.c b/fs/nfs/callback.c
index 42a0c2f1e785..4ffa1f469e90 100644
--- a/fs/nfs/callback.c
+++ b/fs/nfs/callback.c
@@ -78,7 +78,7 @@ nfs4_callback_svc(void *vrqstp)
set_freezable();
- while (!kthread_should_stop())
+ while (!svc_thread_should_stop(rqstp))
svc_recv(rqstp);
svc_exit_thread(rqstp);
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 5ca748309c26..ef0330305cbf 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1329,7 +1329,8 @@ extern void nfs_sb_deactive(struct super_block *sb);
* setup a work entry in the ssc delayed unmount list.
*/
static __be32 nfsd4_ssc_setup_dul(struct nfsd_net *nn, char *ipaddr,
- struct nfsd4_ssc_umount_item **nsui)
+ struct nfsd4_ssc_umount_item **nsui,
+ struct svc_rqst *rqstp)
{
struct nfsd4_ssc_umount_item *ni = NULL;
struct nfsd4_ssc_umount_item *work = NULL;
@@ -1351,7 +1352,7 @@ static __be32 nfsd4_ssc_setup_dul(struct nfsd_net *nn, char *ipaddr,
spin_unlock(&nn->nfsd_ssc_lock);
/* allow 20secs for mount/unmount for now - revisit */
- if (kthread_should_stop() ||
+ if (svc_thread_should_stop(rqstp) ||
(schedule_timeout(20*HZ) == 0)) {
finish_wait(&nn->nfsd_ssc_waitq, &wait);
kfree(work);
@@ -1467,7 +1468,7 @@ nfsd4_interssc_connect(struct nl4_server *nss, struct svc_rqst *rqstp,
goto out_free_rawdata;
snprintf(dev_name, len + 5, "%s%s%s:/", startsep, ipaddr, endsep);
- status = nfsd4_ssc_setup_dul(nn, ipaddr, nsui);
+ status = nfsd4_ssc_setup_dul(nn, ipaddr, nsui, rqstp);
if (status)
goto out_free_devname;
if ((*nsui)->nsui_vfsmount)
@@ -1642,6 +1643,7 @@ static ssize_t _nfsd_copy_file_range(struct nfsd4_copy *copy,
if (bytes_total == 0)
bytes_total = ULLONG_MAX;
do {
+ /* Only async copies can be stopped here */
if (kthread_should_stop())
break;
bytes_copied = nfsd_copy_file_range(src, src_pos, dst, dst_pos,
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index 1582af33e204..062f51fe4dfb 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -957,7 +957,7 @@ nfsd(void *vrqstp)
/*
* The main request loop
*/
- while (!kthread_should_stop()) {
+ while (!svc_thread_should_stop(rqstp)) {
/* Update sv_maxconn if it has changed */
rqstp->rq_server->sv_maxconn = nn->max_connections;
diff --git a/include/linux/lockd/lockd.h b/include/linux/lockd/lockd.h
index 0f016d69c996..9f565416d186 100644
--- a/include/linux/lockd/lockd.h
+++ b/include/linux/lockd/lockd.h
@@ -282,7 +282,7 @@ __be32 nlmsvc_testlock(struct svc_rqst *, struct nlm_file *,
struct nlm_host *, struct nlm_lock *,
struct nlm_lock *, struct nlm_cookie *);
__be32 nlmsvc_cancel_blocked(struct net *net, struct nlm_file *, struct nlm_lock *);
-void nlmsvc_retry_blocked(void);
+void nlmsvc_retry_blocked(struct svc_rqst *rqstp);
void nlmsvc_traverse_blocks(struct nlm_host *, struct nlm_file *,
nlm_host_match_fn_t match);
void nlmsvc_grant_reply(struct nlm_cookie *, __be32);
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index acbe1314febd..0ec691070e27 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -50,6 +50,8 @@ struct svc_pool {
enum {
SP_TASK_PENDING, /* still work to do even if no xprt is queued */
SP_CONGESTED, /* all threads are busy, none idle */
+ SP_NEED_VICTIM, /* One thread needs to agree to exit */
+ SP_VICTIM_REMAINS, /* One thread needs to actually exit */
};
@@ -259,7 +261,7 @@ enum {
RQ_DROPME, /* drop current reply */
RQ_SPLICE_OK, /* turned off in gss privacy to prevent
* encrypting page cache pages */
- RQ_VICTIM, /* about to be shut down */
+ RQ_VICTIM, /* Have agreed to shut down */
RQ_BUSY, /* request is busy */
RQ_DATA, /* request has data */
};
@@ -299,6 +301,28 @@ static inline struct sockaddr *svc_daddr(const struct svc_rqst *rqst)
return (struct sockaddr *) &rqst->rq_daddr;
}
+/**
+ * svc_thread_should_stop - check if this thread should stop
+ * @rqstp: the thread that might need to stop
+ *
+ * To stop an svc thread, the pool flags SP_NEED_VICTIM and SP_VICTIM_REMAINS
+ * are set. The first thread which sees SP_NEED_VICTIM clears it, becoming
+ * the victim using this function. It should then promptly call
+ * svc_exit_thread() to complete the process, clearing SP_VICTIM_REMAINS
+ * so the task waiting for a thread to exit can wake and continue.
+ *
+ * Return values:
+ * %true: caller should invoke svc_exit_thread()
+ * %false: caller should do nothing
+ */
+static inline bool svc_thread_should_stop(struct svc_rqst *rqstp)
+{
+ if (test_and_clear_bit(SP_NEED_VICTIM, &rqstp->rq_pool->sp_flags))
+ set_bit(RQ_VICTIM, &rqstp->rq_flags);
+
+ return test_bit(RQ_VICTIM, &rqstp->rq_flags);
+}
+
struct svc_deferred_req {
u32 prot; /* protocol (UDP or TCP) */
struct svc_xprt *xprt;
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index b98a159eb17f..db579bbc0a0a 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -725,19 +725,22 @@ svc_pool_next(struct svc_serv *serv, struct svc_pool *pool, unsigned int *state)
return pool ? pool : &serv->sv_pools[(*state)++ % serv->sv_nrpools];
}
-static struct task_struct *
+static struct svc_pool *
svc_pool_victim(struct svc_serv *serv, struct svc_pool *pool, unsigned int *state)
{
unsigned int i;
- struct task_struct *task = NULL;
if (pool != NULL) {
spin_lock_bh(&pool->sp_lock);
+ if (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 (!list_empty(&pool->sp_all_threads))
+ if (pool->sp_nrthreads)
goto found_pool;
spin_unlock_bh(&pool->sp_lock);
}
@@ -745,16 +748,10 @@ svc_pool_victim(struct svc_serv *serv, struct svc_pool *pool, unsigned int *stat
}
found_pool:
- if (!list_empty(&pool->sp_all_threads)) {
- struct svc_rqst *rqstp;
-
- rqstp = list_entry(pool->sp_all_threads.next, struct svc_rqst, rq_all);
- set_bit(RQ_VICTIM, &rqstp->rq_flags);
- list_del_rcu(&rqstp->rq_all);
- task = rqstp->rq_task;
- }
+ set_bit(SP_VICTIM_REMAINS, &pool->sp_flags);
+ set_bit(SP_NEED_VICTIM, &pool->sp_flags);
spin_unlock_bh(&pool->sp_lock);
- return task;
+ return pool;
}
static int
@@ -795,18 +792,16 @@ svc_start_kthreads(struct svc_serv *serv, struct svc_pool *pool, int nrservs)
static int
svc_stop_kthreads(struct svc_serv *serv, struct svc_pool *pool, int nrservs)
{
- struct svc_rqst *rqstp;
- struct task_struct *task;
unsigned int state = serv->sv_nrthreads-1;
+ struct svc_pool *victim;
do {
- task = svc_pool_victim(serv, pool, &state);
- if (task == NULL)
+ victim = svc_pool_victim(serv, pool, &state);
+ if (!victim)
break;
- rqstp = kthread_data(task);
- /* Did we lose a race to svo_function threadfn? */
- if (kthread_stop(task) == -EINTR)
- svc_exit_thread(rqstp);
+ svc_pool_wake_idle_thread(victim);
+ wait_on_bit(&victim->sp_flags, SP_VICTIM_REMAINS,
+ TASK_IDLE);
nrservs++;
} while (nrservs < 0);
return 0;
@@ -926,8 +921,7 @@ svc_exit_thread(struct svc_rqst *rqstp)
spin_lock_bh(&pool->sp_lock);
pool->sp_nrthreads--;
- if (!test_and_set_bit(RQ_VICTIM, &rqstp->rq_flags))
- list_del_rcu(&rqstp->rq_all);
+ list_del_rcu(&rqstp->rq_all);
spin_unlock_bh(&pool->sp_lock);
spin_lock_bh(&serv->sv_lock);
@@ -938,6 +932,11 @@ svc_exit_thread(struct svc_rqst *rqstp)
svc_rqst_free(rqstp);
svc_put(serv);
+ /* That svc_put() cannot be the last, because the thread
+ * waiting for SP_VICTIM_REMAINS to clear must hold
+ * a reference. So it is still safe to access pool.
+ */
+ clear_and_wake_up_bit(SP_VICTIM_REMAINS, &pool->sp_flags);
}
EXPORT_SYMBOL_GPL(svc_exit_thread);
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index b057f1cbe7a1..b8539545fefd 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -9,7 +9,6 @@
#include <linux/sched/mm.h>
#include <linux/errno.h>
#include <linux/freezer.h>
-#include <linux/kthread.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <linux/sunrpc/addr.h>
@@ -675,7 +674,7 @@ static bool svc_alloc_arg(struct svc_rqst *rqstp)
continue;
set_current_state(TASK_IDLE);
- if (kthread_should_stop()) {
+ if (svc_thread_should_stop(rqstp)) {
set_current_state(TASK_RUNNING);
return false;
}
@@ -713,7 +712,7 @@ rqst_should_sleep(struct svc_rqst *rqstp)
return false;
/* are we shutting down? */
- if (kthread_should_stop())
+ if (svc_thread_should_stop(rqstp))
return false;
/* are we freezing? */
@@ -858,7 +857,7 @@ void svc_recv(struct svc_rqst *rqstp)
clear_bit(SP_TASK_PENDING, &pool->sp_flags);
- if (kthread_should_stop())
+ if (svc_thread_should_stop(rqstp))
return;
rqstp->rq_xprt = svc_xprt_dequeue(pool);
