[tip: sched/core] sched: Simplify: migrate_swap_stop()

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     5bb76f1ddf2a7dd98f5a89d7755600ed1b4a7fcd
Gitweb:        https://git.kernel.org/tip/5bb76f1ddf2a7dd98f5a89d7755600ed1b4a7fcd
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Tue, 01 Aug 2023 22:41:24 +02:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Mon, 14 Aug 2023 17:01:25 +02:00

sched: Simplify: migrate_swap_stop()

Use guards to reduce gotos and simplify control flow.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Valentin Schneider <vschneid@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230801211811.964370836@xxxxxxxxxxxxx
---
 kernel/sched/core.c  | 23 +++++++----------------
 kernel/sched/sched.h | 20 ++++++++++++++++++++
 2 files changed, 27 insertions(+), 16 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 6e8a8e9..66478a6 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3433,7 +3433,6 @@ static int migrate_swap_stop(void *data)
 {
 	struct migration_swap_arg *arg = data;
 	struct rq *src_rq, *dst_rq;
-	int ret = -EAGAIN;
 
 	if (!cpu_active(arg->src_cpu) || !cpu_active(arg->dst_cpu))
 		return -EAGAIN;
@@ -3441,33 +3440,25 @@ static int migrate_swap_stop(void *data)
 	src_rq = cpu_rq(arg->src_cpu);
 	dst_rq = cpu_rq(arg->dst_cpu);
 
-	double_raw_lock(&arg->src_task->pi_lock,
-			&arg->dst_task->pi_lock);
-	double_rq_lock(src_rq, dst_rq);
+	guard(double_raw_spinlock)(&arg->src_task->pi_lock, &arg->dst_task->pi_lock);
+	guard(double_rq_lock)(src_rq, dst_rq);
 
 	if (task_cpu(arg->dst_task) != arg->dst_cpu)
-		goto unlock;
+		return -EAGAIN;
 
 	if (task_cpu(arg->src_task) != arg->src_cpu)
-		goto unlock;
+		return -EAGAIN;
 
 	if (!cpumask_test_cpu(arg->dst_cpu, arg->src_task->cpus_ptr))
-		goto unlock;
+		return -EAGAIN;
 
 	if (!cpumask_test_cpu(arg->src_cpu, arg->dst_task->cpus_ptr))
-		goto unlock;
+		return -EAGAIN;
 
 	__migrate_swap_task(arg->src_task, arg->dst_cpu);
 	__migrate_swap_task(arg->dst_task, arg->src_cpu);
 
-	ret = 0;
-
-unlock:
-	double_rq_unlock(src_rq, dst_rq);
-	raw_spin_unlock(&arg->dst_task->pi_lock);
-	raw_spin_unlock(&arg->src_task->pi_lock);
-
-	return ret;
+	return 0;
 }
 
 /*
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 9c5035c..c299a58 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2614,6 +2614,12 @@ static inline void double_rq_clock_clear_update(struct rq *rq1, struct rq *rq2)
 static inline void double_rq_clock_clear_update(struct rq *rq1, struct rq *rq2) {}
 #endif
 
+#define DEFINE_LOCK_GUARD_2(name, type, _lock, _unlock, ...)		\
+__DEFINE_UNLOCK_GUARD(name, type, _unlock, type *lock2; __VA_ARGS__) \
+static inline class_##name##_t class_##name##_constructor(type *lock, type *lock2) \
+{ class_##name##_t _t = { .lock = lock, .lock2 = lock2 }, *_T = &_t;	\
+  _lock; return _t; }
+
 #ifdef CONFIG_SMP
 
 static inline bool rq_order_less(struct rq *rq1, struct rq *rq2)
@@ -2743,6 +2749,16 @@ static inline void double_raw_lock(raw_spinlock_t *l1, raw_spinlock_t *l2)
 	raw_spin_lock_nested(l2, SINGLE_DEPTH_NESTING);
 }
 
+static inline void double_raw_unlock(raw_spinlock_t *l1, raw_spinlock_t *l2)
+{
+	raw_spin_unlock(l1);
+	raw_spin_unlock(l2);
+}
+
+DEFINE_LOCK_GUARD_2(double_raw_spinlock, raw_spinlock_t,
+		    double_raw_lock(_T->lock, _T->lock2),
+		    double_raw_unlock(_T->lock, _T->lock2))
+
 /*
  * double_rq_unlock - safely unlock two runqueues
  *
@@ -2800,6 +2816,10 @@ static inline void double_rq_unlock(struct rq *rq1, struct rq *rq2)
 
 #endif
 
+DEFINE_LOCK_GUARD_2(double_rq_lock, struct rq,
+		    double_rq_lock(_T->lock, _T->lock2),
+		    double_rq_unlock(_T->lock, _T->lock2))
+
 extern struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq);
 extern struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq);