Attachment 150237 Details for Bug 217067 – kernel-2.6.9-futex-queue_me-change.patch

kernel-2.6.9-futex-queue_me-change.patch

kernel-2.6.9-futex-queue_me-change.patch (text/plain), 3.21 KB, created by IBM Bug Proxy on 2007-03-16 15:22:15 UTC

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Creator: IBM Bug Proxy

Created: 2007-03-16 15:22:15 UTC

Size: 3.21 KB

patch

obsolete

>--- kernel-2.6.9/linux-2.6.9/kernel/futex.c.futex-enqueue-change	2007-03-14 10:09:11.000000000 -0700
>+++ kernel-2.6.9/linux-2.6.9/kernel/futex.c	2007-03-15 10:10:26.000000000 -0700
>@@ -446,10 +446,10 @@
>  * exactly once.  They are called with the hashed spinlock held.
>  */
> 
>-/* The key must be already stored in q->key. */
>-static void queue_me(struct futex_q *q, int fd, struct file *filp)
>+static inline struct futex_hash_bucket *
>+queue_lock(struct futex_q *q, int fd, struct file *filp)
> {
>-	struct futex_hash_bucket *bh;
>+	struct futex_hash_bucket *hb;
> 
> 	q->fd = fd;
> 	q->filp = filp;
>@@ -457,13 +457,36 @@
> 	init_waitqueue_head(&q->waiters);
> 
> 	get_key_refs(&q->key);
>-	bh = hash_futex(&q->key);
>-	q->lock_ptr = &bh->lock;
>+	hb = hash_futex(&q->key);
>+	q->lock_ptr = &hb->lock;
>+
>+	spin_lock(&hb->lock);
>+	return hb;
>+}
>+
>+static inline void __queue_me(struct futex_q *q, struct futex_hash_bucket *hb)
>+{
>+	list_add_tail(&q->list, &hb->chain);
>+	hb->nqueued++;
>+	spin_unlock(&hb->lock);
>+}
>+
>+static inline void
>+queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb)
>+{
>+	spin_unlock(&hb->lock);
>+	drop_key_refs(&q->key);
>+}
>+
>+
>+/* The key must be already stored in q->key. */
>+static void queue_me(struct futex_q *q, int fd, struct file *filp)
>+{
>+	struct futex_hash_bucket *hb;
>+
>+	hb = queue_lock(q, fd, filp);
>+	__queue_me(q, hb);
> 
>-	spin_lock(&bh->lock);
>-	bh->nqueued++;
>-	list_add_tail(&q->list, &bh->chain);
>-	spin_unlock(&bh->lock);
> }
> 
> /* Return 1 if we were still queued (ie. 0 means we were woken) */
>@@ -475,6 +498,7 @@
> 	/* In the common case we don't take the spinlock, which is nice. */
>  retry:
> 	lock_ptr = q->lock_ptr;
>+	barrier();
> 	if (lock_ptr != 0) {
> 		spin_lock(lock_ptr);
> 		/*
>@@ -506,7 +530,9 @@
> 
> static int futex_wait(unsigned long uaddr, int val, unsigned long time)
> {
>-	DECLARE_WAITQUEUE(wait, current);
>+	struct task_struct *curr = current;
>+	DECLARE_WAITQUEUE(wait, curr);
>+	struct futex_hash_bucket *hb;
> 	int ret, curval;
> 	struct futex_q q;
> 
>@@ -517,7 +543,7 @@
> 	if (unlikely(ret != 0))
> 		goto out_release_sem;
> 
>-	queue_me(&q, -1, NULL);
>+	hb = queue_lock(&q, -1, NULL);
> 
> 	/*
> 	 * Access the page after the futex is queued.
>@@ -528,25 +554,27 @@
> 	ret = get_futex_value_locked(&curval, (int __user *)uaddr);
> 
> 	if (unlikely(ret)) {
>+		queue_unlock(&q, hb);
>+
> 		/* If we would have faulted, release mmap_sem, fault it in and
> 		 * start all over again.
> 		 */
> 		up_read(&current->mm->mmap_sem);
> 
>-		if (!unqueue_me(&q)) /* There's a chance we got woken already */
>-			return 0;
>-
> 		ret = get_user(curval, (int __user *)uaddr);
> 
> 		if (!ret)
> 			goto retry;
> 		return ret;
> 	}
>+	ret = -EWOULDBLOCK;
> 	if (curval != val) {
>-		ret = -EWOULDBLOCK;
>-		goto out_unqueue;
>+		goto out_unlock_release_sem;
> 	}
> 
>+	/* Only actually queue if *uaddr contained val.  */
>+	__queue_me(&q, hb);
>+
> 	/*
> 	 * Now the futex is queued and we have checked the data, we
> 	 * don't want to hold mmap_sem while we sleep.
>@@ -587,10 +615,9 @@
> 	 * have handled it for us already. */
> 	return -EINTR;
> 
>- out_unqueue:
>-	/* If we were woken (and unqueued), we succeeded, whatever. */
>-	if (!unqueue_me(&q))
>-		ret = 0;
>+ out_unlock_release_sem:
>+	queue_unlock(&q, hb);
>+
>  out_release_sem:
> 	up_read(&current->mm->mmap_sem);
> 	return ret;

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