[PATCH] futex: Consolidate duplicated timer setup code

[PATCH] futex: Consolidate duplicated timer setup code

[Waiman Long]

A new futex_setup_timer() helper function is added to consolidate all
the hrtimer_sleeper setup code.

Signed-off-by: Waiman Long <longman@redhat.com>
---
 kernel/futex.c | 67 ++++++++++++++++++++++++++++----------------------
 1 file changed, 37 insertions(+), 30 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index a0514e01c3eb..d24679d75270 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -486,6 +486,35 @@ enum futex_access {
 	FUTEX_WRITE
 };
 
+/**
+ * futex_setup_timer - set up the sleeping hrtimer.
+ * @time:	ptr to the given timeout value
+ * @timeout:	the hrtimer_sleeper structure to be set up
+ * @flags:	futex flags
+ * @range_ns:	optional range in ns
+ *
+ * Return: Initialized hrtimer_sleeper structure or NULL if no timeout
+ *	   value given
+ */
+static inline struct hrtimer_sleeper *
+futex_setup_timer(ktime_t *time, struct hrtimer_sleeper *timeout,
+		  int flags, u64 range_ns)
+{
+	if (!time)
+		return NULL;
+
+	hrtimer_init_on_stack(&timeout->timer, (flags & FLAGS_CLOCKRT) ?
+			      CLOCK_REALTIME : CLOCK_MONOTONIC,
+			      HRTIMER_MODE_ABS);
+	hrtimer_init_sleeper(timeout, current);
+	if (range_ns)
+		hrtimer_set_expires_range_ns(&timeout->timer, *time, range_ns);
+	else
+		hrtimer_set_expires(&timeout->timer, *time);
+
+	return timeout;
+}
+
 /**
  * get_futex_key() - Get parameters which are the keys for a futex
  * @uaddr:	virtual address of the futex
@@ -2679,7 +2708,7 @@ static int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
 static int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val,
 		      ktime_t *abs_time, u32 bitset)
 {
-	struct hrtimer_sleeper timeout, *to = NULL;
+	struct hrtimer_sleeper timeout, *to;
 	struct restart_block *restart;
 	struct futex_hash_bucket *hb;
 	struct futex_q q = futex_q_init;
@@ -2689,17 +2718,8 @@ static int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val,
 		return -EINVAL;
 	q.bitset = bitset;
 
-	if (abs_time) {
-		to = &timeout;
-
-		hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ?
-				      CLOCK_REALTIME : CLOCK_MONOTONIC,
-				      HRTIMER_MODE_ABS);
-		hrtimer_init_sleeper(to, current);
-		hrtimer_set_expires_range_ns(&to->timer, *abs_time,
-					     current->timer_slack_ns);
-	}
-
+	to = futex_setup_timer(abs_time, &timeout, flags,
+			       current->timer_slack_ns);
 retry:
 	/*
 	 * Prepare to wait on uaddr. On success, holds hb lock and increments
@@ -2779,7 +2799,7 @@ static long futex_wait_restart(struct restart_block *restart)
 static int futex_lock_pi(u32 __user *uaddr, unsigned int flags,
 			 ktime_t *time, int trylock)
 {
-	struct hrtimer_sleeper timeout, *to = NULL;
+	struct hrtimer_sleeper timeout, *to;
 	struct futex_pi_state *pi_state = NULL;
 	struct rt_mutex_waiter rt_waiter;
 	struct futex_hash_bucket *hb;
@@ -2792,13 +2812,7 @@ static int futex_lock_pi(u32 __user *uaddr, unsigned int flags,
 	if (refill_pi_state_cache())
 		return -ENOMEM;
 
-	if (time) {
-		to = &timeout;
-		hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME,
-				      HRTIMER_MODE_ABS);
-		hrtimer_init_sleeper(to, current);
-		hrtimer_set_expires(&to->timer, *time);
-	}
+	to = futex_setup_timer(time, &timeout, FLAGS_CLOCKRT, 0);
 
 retry:
 	ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key, FUTEX_WRITE);
@@ -3182,7 +3196,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
 				 u32 val, ktime_t *abs_time, u32 bitset,
 				 u32 __user *uaddr2)
 {
-	struct hrtimer_sleeper timeout, *to = NULL;
+	struct hrtimer_sleeper timeout, *to;
 	struct futex_pi_state *pi_state = NULL;
 	struct rt_mutex_waiter rt_waiter;
 	struct futex_hash_bucket *hb;
@@ -3199,15 +3213,8 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
 	if (!bitset)
 		return -EINVAL;
 
-	if (abs_time) {
-		to = &timeout;
-		hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ?
-				      CLOCK_REALTIME : CLOCK_MONOTONIC,
-				      HRTIMER_MODE_ABS);
-		hrtimer_init_sleeper(to, current);
-		hrtimer_set_expires_range_ns(&to->timer, *abs_time,
-					     current->timer_slack_ns);
-	}
+	to = futex_setup_timer(abs_time, &timeout, flags,
+			       current->timer_slack_ns);
 
 	/*
 	 * The waiter is allocated on our stack, manipulated by the requeue
-- 
2.18.1

Re: [PATCH] futex: Consolidate duplicated timer setup code

[Peter Zijlstra]

On Wed, Apr 24, 2019 at 11:36:51AM -0400, Waiman Long wrote:
> +static inline struct hrtimer_sleeper *
> +futex_setup_timer(ktime_t *time, struct hrtimer_sleeper *timeout,
> +		  int flags, u64 range_ns)
> +{
> +	if (!time)
> +		return NULL;
> +
> +	hrtimer_init_on_stack(&timeout->timer, (flags & FLAGS_CLOCKRT) ?
> +			      CLOCK_REALTIME : CLOCK_MONOTONIC,
> +			      HRTIMER_MODE_ABS);
> +	hrtimer_init_sleeper(timeout, current);
> +	if (range_ns)
> +		hrtimer_set_expires_range_ns(&timeout->timer, *time, range_ns);
> +	else
> +		hrtimer_set_expires(&timeout->timer, *time);

That can be an unconditinoal:

	hrtimer_set_expires_range_ns(&timeout->timer, *time, range_ns);

See how:

  timer->node.expires = ktime_add_safe(time, ns_to_ktime(delta));

is the same as:

  timer->node.expires = time;

when !delta.

> +
> +	return timeout;
> +}

Anyway, looks good otherwise.

Re: [PATCH] futex: Consolidate duplicated timer setup code

[Waiman Long]

On 4/24/19 12:09 PM, Peter Zijlstra wrote:
> On Wed, Apr 24, 2019 at 11:36:51AM -0400, Waiman Long wrote:
>> +static inline struct hrtimer_sleeper *
>> +futex_setup_timer(ktime_t *time, struct hrtimer_sleeper *timeout,
>> +		  int flags, u64 range_ns)
>> +{
>> +	if (!time)
>> +		return NULL;
>> +
>> +	hrtimer_init_on_stack(&timeout->timer, (flags & FLAGS_CLOCKRT) ?
>> +			      CLOCK_REALTIME : CLOCK_MONOTONIC,
>> +			      HRTIMER_MODE_ABS);
>> +	hrtimer_init_sleeper(timeout, current);
>> +	if (range_ns)
>> +		hrtimer_set_expires_range_ns(&timeout->timer, *time, range_ns);
>> +	else
>> +		hrtimer_set_expires(&timeout->timer, *time);
> That can be an unconditinoal:
>
> 	hrtimer_set_expires_range_ns(&timeout->timer, *time, range_ns);
>
> See how:
>
>   timer->node.expires = ktime_add_safe(time, ns_to_ktime(delta));
>
> is the same as:
>
>   timer->node.expires = time;
>
> when !delta.


That is true. I will update it accordingly.

Thanks,
Longman