[PATCH] Add kthread_stop_sem()

Enhance the kthread API by adding kthread_stop_sem, for use in stopping
threads that spend their idle time waiting on a semaphore.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index 3fa7864..ebdd41f 100644 (file)
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -70,6 +70,18 @@ void kthread_bind(struct task_struct *k, unsigned int cpu);
 int kthread_stop(struct task_struct *k);
 
 /**
+ * kthread_stop_sem: stop a thread created by kthread_create().
+ * @k: thread created by kthread_create().
+ * @s: semaphore that @k waits on while idle.
+ *
+ * Does essentially the same thing as kthread_stop() above, but wakes
+ * @k by calling up(@s).
+ *
+ * Returns the result of threadfn(), or -EINTR if wake_up_process()
+ * was never called. */
+int kthread_stop_sem(struct task_struct *k, struct semaphore *s);
+
+/**
  * kthread_should_stop: should this kthread return now?
  *
  * When someone calls kthread_stop on your kthread, it will be woken

diff --git a/kernel/kthread.c b/kernel/kthread.c
index f50f174..e75950a 100644 (file)
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -165,6 +165,12 @@ EXPORT_SYMBOL(kthread_bind);
 
 int kthread_stop(struct task_struct *k)
 {
+       return kthread_stop_sem(k, NULL);
+}
+EXPORT_SYMBOL(kthread_stop);
+
+int kthread_stop_sem(struct task_struct *k, struct semaphore *s)
+{
        int ret;
 
        down(&kthread_stop_lock);
@@ -178,7 +184,10 @@ int kthread_stop(struct task_struct *k)
 
        /* Now set kthread_should_stop() to true, and wake it up. */
        kthread_stop_info.k = k;
-       wake_up_process(k);
+       if (s)
+               up(s);
+       else
+               wake_up_process(k);
        put_task_struct(k);
 
        /* Once it dies, reset stop ptr, gather result and we're done. */
@@ -189,7 +198,7 @@ int kthread_stop(struct task_struct *k)
 
        return ret;
 }
-EXPORT_SYMBOL(kthread_stop);
+EXPORT_SYMBOL(kthread_stop_sem);
 
 static __init int helper_init(void)
 {