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lockd: close potential race with rapid lockd_up/lockd_down cycle

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If lockd_down is called very rapidly after lockd_up returns, then
there is a slim chance that lockd() will never be called. kthread()
will return before calling the function, so we'll end up never
actually calling the cleanup functions for the thread.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
This commit is contained in:
Jeff Layton
2008-06-11 10:03:12 -04:00
committed by J. Bruce Fields
parent a75c5d01e4
commit abd1ec4efd
1 changed files with 13 additions and 20 deletions
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33
fs/lockd/svc.c
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@@ -50,7 +50,7 @@ EXPORT_SYMBOL(nlmsvc_ops);
static DEFINE_MUTEX(nlmsvc_mutex); static DEFINE_MUTEX(nlmsvc_mutex);
static unsigned int nlmsvc_users; static unsigned int nlmsvc_users;
static struct task_struct *nlmsvc_task; static struct task_struct *nlmsvc_task;
static struct svc_serv *nlmsvc_serv; static struct svc_rqst *nlmsvc_rqst;
int nlmsvc_grace_period; int nlmsvc_grace_period;
unsigned long nlmsvc_timeout; unsigned long nlmsvc_timeout;
@@ -194,20 +194,11 @@ lockd(void *vrqstp)
svc_process(rqstp); svc_process(rqstp);
} }
flush_signals(current); flush_signals(current);
if (nlmsvc_ops) if (nlmsvc_ops)
nlmsvc_invalidate_all(); nlmsvc_invalidate_all();
nlm_shutdown_hosts(); nlm_shutdown_hosts();
unlock_kernel(); unlock_kernel();
nlmsvc_task = NULL;
nlmsvc_serv = NULL;
/* Exit the RPC thread */
svc_exit_thread(rqstp);
return 0; return 0;
} }
@@ -254,16 +245,15 @@ int
lockd_up(int proto) /* Maybe add a 'family' option when IPv6 is supported ?? */ lockd_up(int proto) /* Maybe add a 'family' option when IPv6 is supported ?? */
{ {
struct svc_serv *serv; struct svc_serv *serv;
struct svc_rqst *rqstp;
int error = 0; int error = 0;
mutex_lock(&nlmsvc_mutex); mutex_lock(&nlmsvc_mutex);
/* /*
* Check whether we're already up and running. * Check whether we're already up and running.
*/ */
if (nlmsvc_serv) { if (nlmsvc_rqst) {
if (proto) if (proto)
error = make_socks(nlmsvc_serv, proto); error = make_socks(nlmsvc_rqst->rq_server, proto);
goto out; goto out;
} }
@@ -288,9 +278,10 @@ lockd_up(int proto) /* Maybe add a 'family' option when IPv6 is supported ?? */
/* /*
* Create the kernel thread and wait for it to start. * Create the kernel thread and wait for it to start.
*/ */
rqstp = svc_prepare_thread(serv, &serv->sv_pools[0]); nlmsvc_rqst = svc_prepare_thread(serv, &serv->sv_pools[0]);
if (IS_ERR(rqstp)) { if (IS_ERR(nlmsvc_rqst)) {
error = PTR_ERR(rqstp); error = PTR_ERR(nlmsvc_rqst);
nlmsvc_rqst = NULL;
printk(KERN_WARNING printk(KERN_WARNING
"lockd_up: svc_rqst allocation failed, error=%d\n", "lockd_up: svc_rqst allocation failed, error=%d\n",
error); error);
@@ -298,16 +289,15 @@ lockd_up(int proto) /* Maybe add a 'family' option when IPv6 is supported ?? */
} }
svc_sock_update_bufs(serv); svc_sock_update_bufs(serv);
nlmsvc_serv = rqstp->rq_server;
nlmsvc_task = kthread_run(lockd, rqstp, serv->sv_name); nlmsvc_task = kthread_run(lockd, nlmsvc_rqst, serv->sv_name);
if (IS_ERR(nlmsvc_task)) { if (IS_ERR(nlmsvc_task)) {
error = PTR_ERR(nlmsvc_task); error = PTR_ERR(nlmsvc_task);
svc_exit_thread(nlmsvc_rqst);
nlmsvc_task = NULL; nlmsvc_task = NULL;
nlmsvc_serv = NULL; nlmsvc_rqst = NULL;
printk(KERN_WARNING printk(KERN_WARNING
"lockd_up: kthread_run failed, error=%d\n", error); "lockd_up: kthread_run failed, error=%d\n", error);
svc_exit_thread(rqstp);
goto destroy_and_out; goto destroy_and_out;
} }
@@ -346,6 +336,9 @@ lockd_down(void)
BUG(); BUG();
} }
kthread_stop(nlmsvc_task); kthread_stop(nlmsvc_task);
svc_exit_thread(nlmsvc_rqst);
nlmsvc_task = NULL;
nlmsvc_rqst = NULL;
out: out:
mutex_unlock(&nlmsvc_mutex); mutex_unlock(&nlmsvc_mutex);
} }