2008-01-25 09:41:21

by Eric Sesterhenn

Subject: [Patch] Removal of FUTEX_FD

hi,

since FUTEX_FD was scheduled for removal in June 2007 lets remove it.
Google Code search found no users for it and NGPT was abandoned in 2003
according to IBM. futex.h is left untouched to make sure the id does
not get reassigned. Since queue_me() has no users left it is commented
out to avoid a warning, i didnt remove it completely since it is part
of the internal api (matching unqueue_me())

Signed-off-by: Eric Sesterhenn <[email protected]>

--- linux/kernel/futex.c.orig 2008-01-25 09:53:28.000000000 +0100
+++ linux/kernel/futex.c 2008-01-25 10:01:53.000000000 +0100
@@ -1026,6 +1026,7 @@ queue_unlock(struct futex_q *q, struct f
* exactly once. They are called with the hashed spinlock held.
*/

+#if 0
/* The key must be already stored in q->key. */
static void queue_me(struct futex_q *q, int fd, struct file *filp)
{
@@ -1034,6 +1035,7 @@ static void queue_me(struct futex_q *q,
hb = queue_lock(q, fd, filp);
__queue_me(q, hb);
}
+#endif

/* Return 1 if we were still queued (ie. 0 means we were woken) */
static int unqueue_me(struct futex_q *q)
@@ -1750,87 +1752,6 @@ static const struct file_operations fute
};

/*
- * Signal allows caller to avoid the race which would occur if they
- * set the sigio stuff up afterwards.
- */
-static int futex_fd(u32 __user *uaddr, int signal)
-{
- struct futex_q *q;
- struct file *filp;
- int ret, err;
- struct rw_semaphore *fshared;
- static unsigned long printk_interval;
-
- if (printk_timed_ratelimit(&printk_interval, 60 * 60 * 1000)) {
- printk(KERN_WARNING "Process `%s' used FUTEX_FD, which "
- "will be removed from the kernel in June 2007\n",
- current->comm);
- }
-
- ret = -EINVAL;
- if (!valid_signal(signal))
- goto out;
-
- ret = get_unused_fd();
- if (ret < 0)
- goto out;
- filp = get_empty_filp();
- if (!filp) {
- put_unused_fd(ret);
- ret = -ENFILE;
- goto out;
- }
- filp->f_op = &futex_fops;
- filp->f_path.mnt = mntget(futex_mnt);
- filp->f_path.dentry = dget(futex_mnt->mnt_root);
- filp->f_mapping = filp->f_path.dentry->d_inode->i_mapping;
-
- if (signal) {
- err = __f_setown(filp, task_pid(current), PIDTYPE_PID, 1);
- if (err < 0) {
- goto error;
- }
- filp->f_owner.signum = signal;
- }
-
- q = kmalloc(sizeof(*q), GFP_KERNEL);
- if (!q) {
- err = -ENOMEM;
- goto error;
- }
- q->pi_state = NULL;
-
- fshared = &current->mm->mmap_sem;
- down_read(fshared);
- err = get_futex_key(uaddr, fshared, &q->key);
-
- if (unlikely(err != 0)) {
- up_read(fshared);
- kfree(q);
- goto error;
- }
-
- /*
- * queue_me() must be called before releasing mmap_sem, because
- * key->shared.inode needs to be referenced while holding it.
- */
- filp->private_data = q;
-
- queue_me(q, ret, filp);
- up_read(fshared);
-
- /* Now we map fd to filp, so userspace can access it */
- fd_install(ret, filp);
-out:
- return ret;
-error:
- put_unused_fd(ret);
- put_filp(filp);
- ret = err;
- goto out;
-}
-
-/*
* Support for robust futexes: the kernel cleans up held futexes at
* thread exit time.
*
@@ -2048,10 +1969,6 @@ long do_futex(u32 __user *uaddr, int op,
case FUTEX_WAKE:
ret = futex_wake(uaddr, fshared, val);
break;
- case FUTEX_FD:
- /* non-zero val means F_SETOWN(getpid()) & F_SETSIG(val) */
- ret = futex_fd(uaddr, val);
- break;
case FUTEX_REQUEUE:
ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL);
break;

2008-01-29 05:50:09

by Rusty Russell

Subject: Re: [Patch] Removal of FUTEX_FD

On Friday 25 January 2008 20:40:46 Eric Sesterhenn wrote:
> hi,
>
> since FUTEX_FD was scheduled for removal in June 2007 lets remove it.
> Google Code search found no users for it and NGPT was abandoned in 2003
> according to IBM. futex.h is left untouched to make sure the id does
> not get reassigned. Since queue_me() has no users left it is commented
> out to avoid a warning, i didnt remove it completely since it is part
> of the internal api (matching unqueue_me())

Thanks, I've queued this with a futher cleanup (rename __queue_me to queue_me,
add comments, and remove the old one entirely).

Thanks,
Rusty.