futex: Add sys_futex_wait()

To complement sys_futex_waitv()/wake(), add sys_futex_wait(). This
syscall implements what was previously known as FUTEX_WAIT_BITSET
except it uses 'unsigned long' for the value and bitmask arguments,
takes timespec and clockid_t arguments for the absolute timeout and
uses FUTEX2 flags.

The 'unsigned long' allows FUTEX2_SIZE_U64 on 64bit platforms.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/r/20230921105248.164324363@noisy.programming.kicks-ass.net

1 files changed, 36 insertions, 25 deletions

diff --git a/kernel/futex/waitwake.c b/kernel/futex/waitwake.c
index ceb05b876597..b109a0810a2c 100644
--- a/kernel/futex/waitwake.c
+++ b/kernel/futex/waitwake.c
@@ -632,20 +632,18 @@ retry_private:
 	return ret;
 }
 
-int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val, ktime_t *abs_time, u32 bitset)
+int __futex_wait(u32 __user *uaddr, unsigned int flags, u32 val,
+		 struct hrtimer_sleeper *to, u32 bitset)
 {
-	struct hrtimer_sleeper timeout, *to;
-	struct restart_block *restart;
-	struct futex_hash_bucket *hb;
 	struct futex_q q = futex_q_init;
+	struct futex_hash_bucket *hb;
 	int ret;
 
 	if (!bitset)
 		return -EINVAL;
+
 	q.bitset = bitset;
 
-	to = futex_setup_timer(abs_time, &timeout, flags,
-			       current->timer_slack_ns);
 retry:
 	/*
 	 * Prepare to wait on uaddr. On success, it holds hb->lock and q
@@ -653,18 +651,17 @@ retry:
 	 */
 	ret = futex_wait_setup(uaddr, val, flags, &q, &hb);
 	if (ret)
-		goto out;
+		return ret;
 
 	/* futex_queue and wait for wakeup, timeout, or a signal. */
 	futex_wait_queue(hb, &q, to);
 
 	/* If we were woken (and unqueued), we succeeded, whatever. */
-	ret = 0;
 	if (!futex_unqueue(&q))
-		goto out;
-	ret = -ETIMEDOUT;
+		return 0;
+
 	if (to && !to->task)
-		goto out;
+		return -ETIMEDOUT;
 
 	/*
 	 * We expect signal_pending(current), but we might be the
@@ -673,24 +670,38 @@ retry:
 	if (!signal_pending(current))
 		goto retry;
 
-	ret = -ERESTARTSYS;
-	if (!abs_time)
-		goto out;
+	return -ERESTARTSYS;
+}
 
-	restart = &current->restart_block;
-	restart->futex.uaddr = uaddr;
-	restart->futex.val = val;
-	restart->futex.time = *abs_time;
-	restart->futex.bitset = bitset;
-	restart->futex.flags = flags | FLAGS_HAS_TIMEOUT;
+int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val, ktime_t *abs_time, u32 bitset)
+{
+	struct hrtimer_sleeper timeout, *to;
+	struct restart_block *restart;
+	int ret;
+
+	to = futex_setup_timer(abs_time, &timeout, flags,
+			       current->timer_slack_ns);
+
+	ret = __futex_wait(uaddr, flags, val, to, bitset);
+
+	/* No timeout, nothing to clean up. */
+	if (!to)
+		return ret;
+
+	hrtimer_cancel(&to->timer);
+	destroy_hrtimer_on_stack(&to->timer);
 
-	ret = set_restart_fn(restart, futex_wait_restart);
+	if (ret == -ERESTARTSYS) {
+		restart = &current->restart_block;
+		restart->futex.uaddr = uaddr;
+		restart->futex.val = val;
+		restart->futex.time = *abs_time;
+		restart->futex.bitset = bitset;
+		restart->futex.flags = flags | FLAGS_HAS_TIMEOUT;
 
-out:
-	if (to) {
-		hrtimer_cancel(&to->timer);
-		destroy_hrtimer_on_stack(&to->timer);
+		return set_restart_fn(restart, futex_wait_restart);
 	}
+
 	return ret;
 }