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authorOleg Nesterov <oleg@redhat.com>2013-04-29 15:05:12 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-04-29 15:54:25 -0700
commitb5c5442bb6bce0c67701d55124be561043a51faf (patch)
treef00a0fdcdb157fa4b8f54c6a31d3935b7c927aa6 /kernel/kthread.c
parent4ecdafc8084fe1d95bb59ed7753b345abcd586fb (diff)
downloadlwn-b5c5442bb6bce0c67701d55124be561043a51faf.tar.gz
lwn-b5c5442bb6bce0c67701d55124be561043a51faf.zip
kthread: kill task_get_live_kthread()
task_get_live_kthread() looks confusing and unneeded. It does get_task_struct() but only kthread_stop() needs this, it can be called even if the calller doesn't have a reference when we know that this kthread can't exit until we do kthread_stop(). kthread_park() and kthread_unpark() do not need get_task_struct(), the callers already have the reference. And it can not help if we can race with the exiting kthread anyway, kthread_park() can hang forever in this case. Change kthread_park() and kthread_unpark() to use to_live_kthread(), change kthread_stop() to do get_task_struct() by hand and remove task_get_live_kthread(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Namhyung Kim <namhyung@kernel.org> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/kthread.c')
-rw-r--r--kernel/kthread.c20
1 files changed, 7 insertions, 13 deletions
diff --git a/kernel/kthread.c b/kernel/kthread.c
index a84dee265f94..9b12d65186f7 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -324,12 +324,6 @@ struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
return p;
}
-static struct kthread *task_get_live_kthread(struct task_struct *k)
-{
- get_task_struct(k);
- return to_live_kthread(k);
-}
-
static void __kthread_unpark(struct task_struct *k, struct kthread *kthread)
{
clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
@@ -356,11 +350,10 @@ static void __kthread_unpark(struct task_struct *k, struct kthread *kthread)
*/
void kthread_unpark(struct task_struct *k)
{
- struct kthread *kthread = task_get_live_kthread(k);
+ struct kthread *kthread = to_live_kthread(k);
if (kthread)
__kthread_unpark(k, kthread);
- put_task_struct(k);
}
/**
@@ -377,7 +370,7 @@ void kthread_unpark(struct task_struct *k)
*/
int kthread_park(struct task_struct *k)
{
- struct kthread *kthread = task_get_live_kthread(k);
+ struct kthread *kthread = to_live_kthread(k);
int ret = -ENOSYS;
if (kthread) {
@@ -390,7 +383,6 @@ int kthread_park(struct task_struct *k)
}
ret = 0;
}
- put_task_struct(k);
return ret;
}
@@ -411,10 +403,13 @@ int kthread_park(struct task_struct *k)
*/
int kthread_stop(struct task_struct *k)
{
- struct kthread *kthread = task_get_live_kthread(k);
+ struct kthread *kthread;
int ret;
trace_sched_kthread_stop(k);
+
+ get_task_struct(k);
+ kthread = to_live_kthread(k);
if (kthread) {
set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
__kthread_unpark(k, kthread);
@@ -422,10 +417,9 @@ int kthread_stop(struct task_struct *k)
wait_for_completion(&kthread->exited);
}
ret = k->exit_code;
-
put_task_struct(k);
- trace_sched_kthread_stop_ret(ret);
+ trace_sched_kthread_stop_ret(ret);
return ret;
}
EXPORT_SYMBOL(kthread_stop);