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NLM: Convert lockd to use kthreads
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Have lockd_up start lockd using kthread_run. With this change,
lockd_down now blocks until lockd actually exits, so there's no longer
need for the waitqueue code at the end of lockd_down. This also means
that only one lockd can be running at a time which simplifies the code
within lockd's main loop.

This also adds a check for kthread_should_stop in the main loop of
nlmsvc_retry_blocked and after that function returns. There's no sense
continuing to retry blocks if lockd is coming down anyway.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
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Jeff Layton authored and J. Bruce Fields committed Apr 23, 2008
1 parent 7086721 commit d751a7c
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Showing 2 changed files with 60 additions and 75 deletions.
132 changes: 58 additions & 74 deletions fs/lockd/svc.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,7 @@
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/mutex.h>
#include <linux/kthread.h>
#include <linux/freezer.h>

#include <linux/sunrpc/types.h>
Expand All @@ -48,14 +49,11 @@ EXPORT_SYMBOL(nlmsvc_ops);

static DEFINE_MUTEX(nlmsvc_mutex);
static unsigned int nlmsvc_users;
static pid_t nlmsvc_pid;
static struct task_struct *nlmsvc_task;
static struct svc_serv *nlmsvc_serv;
int nlmsvc_grace_period;
unsigned long nlmsvc_timeout;

static DECLARE_COMPLETION(lockd_start_done);
static DECLARE_WAIT_QUEUE_HEAD(lockd_exit);

/*
* These can be set at insmod time (useful for NFS as root filesystem),
* and also changed through the sysctl interface. -- Jamie Lokier, Aug 2003
Expand Down Expand Up @@ -111,35 +109,30 @@ static inline void clear_grace_period(void)
/*
* This is the lockd kernel thread
*/
static void
lockd(struct svc_rqst *rqstp)
static int
lockd(void *vrqstp)
{
int err = 0;
struct svc_rqst *rqstp = vrqstp;
unsigned long grace_period_expire;

/* Lock module and set up kernel thread */
/* lockd_up is waiting for us to startup, so will
* be holding a reference to this module, so it
* is safe to just claim another reference
*/
__module_get(THIS_MODULE);
lock_kernel();

/*
* Let our maker know we're running.
*/
nlmsvc_pid = current->pid;
nlmsvc_serv = rqstp->rq_server;
complete(&lockd_start_done);

daemonize("lockd");
/* try_to_freeze() is called from svc_recv() */
set_freezable();

/* Process request with signals blocked, but allow SIGKILL. */
/* Allow SIGKILL to tell lockd to drop all of its locks */
allow_signal(SIGKILL);

dprintk("NFS locking service started (ver " LOCKD_VERSION ").\n");

/*
* FIXME: it would be nice if lockd didn't spend its entire life
* running under the BKL. At the very least, it would be good to
* have someone clarify what it's intended to protect here. I've
* seen some handwavy posts about posix locking needing to be
* done under the BKL, but it's far from clear.
*/
lock_kernel();

if (!nlm_timeout)
nlm_timeout = LOCKD_DFLT_TIMEO;
nlmsvc_timeout = nlm_timeout * HZ;
Expand All @@ -148,10 +141,9 @@ lockd(struct svc_rqst *rqstp)

/*
* The main request loop. We don't terminate until the last
* NFS mount or NFS daemon has gone away, and we've been sent a
* signal, or else another process has taken over our job.
* NFS mount or NFS daemon has gone away.
*/
while ((nlmsvc_users || !signalled()) && nlmsvc_pid == current->pid) {
while (!kthread_should_stop()) {
long timeout = MAX_SCHEDULE_TIMEOUT;
RPC_IFDEBUG(char buf[RPC_MAX_ADDRBUFLEN]);

Expand All @@ -161,6 +153,7 @@ lockd(struct svc_rqst *rqstp)
nlmsvc_invalidate_all();
grace_period_expire = set_grace_period();
}
continue;
}

/*
Expand Down Expand Up @@ -195,28 +188,19 @@ lockd(struct svc_rqst *rqstp)
}

flush_signals(current);
if (nlmsvc_ops)
nlmsvc_invalidate_all();
nlm_shutdown_hosts();

/*
* Check whether there's a new lockd process before
* shutting down the hosts and clearing the slot.
*/
if (!nlmsvc_pid || current->pid == nlmsvc_pid) {
if (nlmsvc_ops)
nlmsvc_invalidate_all();
nlm_shutdown_hosts();
nlmsvc_pid = 0;
nlmsvc_serv = NULL;
} else
printk(KERN_DEBUG
"lockd: new process, skipping host shutdown\n");
wake_up(&lockd_exit);
unlock_kernel();

nlmsvc_task = NULL;
nlmsvc_serv = NULL;

/* Exit the RPC thread */
svc_exit_thread(rqstp);

/* Release module */
unlock_kernel();
module_put_and_exit(0);
return 0;
}

/*
Expand Down Expand Up @@ -261,14 +245,15 @@ static int make_socks(struct svc_serv *serv, int proto)
int
lockd_up(int proto) /* Maybe add a 'family' option when IPv6 is supported ?? */
{
struct svc_serv * serv;
int error = 0;
struct svc_serv *serv;
struct svc_rqst *rqstp;
int error = 0;

mutex_lock(&nlmsvc_mutex);
/*
* Check whether we're already up and running.
*/
if (nlmsvc_pid) {
if (nlmsvc_serv) {
if (proto)
error = make_socks(nlmsvc_serv, proto);
goto out;
Expand All @@ -295,13 +280,28 @@ lockd_up(int proto) /* Maybe add a 'family' option when IPv6 is supported ?? */
/*
* Create the kernel thread and wait for it to start.
*/
error = svc_create_thread(lockd, serv);
if (error) {
rqstp = svc_prepare_thread(serv, &serv->sv_pools[0]);
if (IS_ERR(rqstp)) {
error = PTR_ERR(rqstp);
printk(KERN_WARNING
"lockd_up: create thread failed, error=%d\n", error);
"lockd_up: svc_rqst allocation failed, error=%d\n",
error);
goto destroy_and_out;
}

svc_sock_update_bufs(serv);
nlmsvc_serv = rqstp->rq_server;

nlmsvc_task = kthread_run(lockd, rqstp, serv->sv_name);
if (IS_ERR(nlmsvc_task)) {
error = PTR_ERR(nlmsvc_task);
nlmsvc_task = NULL;
nlmsvc_serv = NULL;
printk(KERN_WARNING
"lockd_up: kthread_run failed, error=%d\n", error);
svc_exit_thread(rqstp);
goto destroy_and_out;
}
wait_for_completion(&lockd_start_done);

/*
* Note: svc_serv structures have an initial use count of 1,
Expand All @@ -323,37 +323,21 @@ EXPORT_SYMBOL(lockd_up);
void
lockd_down(void)
{
static int warned;

mutex_lock(&nlmsvc_mutex);
if (nlmsvc_users) {
if (--nlmsvc_users)
goto out;
} else
printk(KERN_WARNING "lockd_down: no users! pid=%d\n", nlmsvc_pid);

if (!nlmsvc_pid) {
if (warned++ == 0)
printk(KERN_WARNING "lockd_down: no lockd running.\n");
goto out;
} else {
printk(KERN_ERR "lockd_down: no users! task=%p\n",
nlmsvc_task);
BUG();
}
warned = 0;

kill_proc(nlmsvc_pid, SIGKILL, 1);
/*
* Wait for the lockd process to exit, but since we're holding
* the lockd semaphore, we can't wait around forever ...
*/
clear_thread_flag(TIF_SIGPENDING);
interruptible_sleep_on_timeout(&lockd_exit, HZ);
if (nlmsvc_pid) {
printk(KERN_WARNING
"lockd_down: lockd failed to exit, clearing pid\n");
nlmsvc_pid = 0;
if (!nlmsvc_task) {
printk(KERN_ERR "lockd_down: no lockd running.\n");
BUG();
}
spin_lock_irq(&current->sighand->siglock);
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);
kthread_stop(nlmsvc_task);
out:
mutex_unlock(&nlmsvc_mutex);
}
Expand Down
3 changes: 2 additions & 1 deletion fs/lockd/svclock.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,7 @@
#include <linux/sunrpc/svc.h>
#include <linux/lockd/nlm.h>
#include <linux/lockd/lockd.h>
#include <linux/kthread.h>

#define NLMDBG_FACILITY NLMDBG_SVCLOCK

Expand Down Expand Up @@ -887,7 +888,7 @@ nlmsvc_retry_blocked(void)
unsigned long timeout = MAX_SCHEDULE_TIMEOUT;
struct nlm_block *block;

while (!list_empty(&nlm_blocked)) {
while (!list_empty(&nlm_blocked) && !kthread_should_stop()) {
block = list_entry(nlm_blocked.next, struct nlm_block, b_list);

if (block->b_when == NLM_NEVER)
Expand Down

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