sched: Allow sched_class::dequeue_task() to fail

Change the function signature of sched_class::dequeue_task() to return
a boolean, allowing future patches to 'fail' dequeue.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Tested-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lkml.kernel.org/r/20240727105028.864630153@infradead.org

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ab50100363ca81660e0ee81bbad80189aa7df8ee..4f7a4e98f22d69cac813a01150b5b7b75fdd766d 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2001,7 +2001,10 @@ void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
                sched_core_enqueue(rq, p);
 }
 
-void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
+/*
+ * Must only return false when DEQUEUE_SLEEP.
+ */
+inline bool dequeue_task(struct rq *rq, struct task_struct *p, int flags)
 {
        if (sched_core_enabled(rq))
                sched_core_dequeue(rq, p, flags);
@@ -2015,7 +2018,7 @@ void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
        }
 
        uclamp_rq_dec(rq, p);
-       p->sched_class->dequeue_task(rq, p, flags);
+       return p->sched_class->dequeue_task(rq, p, flags);
 }
 
 void activate_task(struct rq *rq, struct task_struct *p, int flags)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index c5f1cc753a31c7210dd347d064257452646d821a..bbaeace9d1e37754c250ce6210a39bf66c2e86f6 100644 (file)
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -2162,7 +2162,7 @@ static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
                enqueue_pushable_dl_task(rq, p);
 }
 
-static void dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
+static bool dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
 {
        update_curr_dl(rq);
 
@@ -2172,6 +2172,8 @@ static void dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
        dequeue_dl_entity(&p->dl, flags);
        if (!p->dl.dl_throttled && !dl_server(&p->dl))
                dequeue_pushable_dl_task(rq, p);
+
+       return true;
 }
 
 /*

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1452c536b578079662a986748529b094f38c8a66..03f76b3a6f1c2585a17f95f2a3675457b9e5fd4e 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6865,7 +6865,7 @@ static void set_next_buddy(struct sched_entity *se);
  * decreased. We remove the task from the rbtree and
  * update the fair scheduling stats:
  */
-static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
+static bool dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 {
        struct cfs_rq *cfs_rq;
        struct sched_entity *se = &p->se;
@@ -6937,6 +6937,8 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 dequeue_throttle:
        util_est_update(&rq->cfs, p, task_sleep);
        hrtick_update(rq);
+
+       return true;
 }
 
 #ifdef CONFIG_SMP

diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index d560f7ffa463f6e82a458634fe216e6c058bd1e3..16074209ce2604f1ecf5527b6e1e8aa4c5acfa6f 100644 (file)
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -482,13 +482,14 @@ struct task_struct *pick_next_task_idle(struct rq *rq)
  * It is not legal to sleep in the idle task - print a warning
  * message if some code attempts to do it:
  */
-static void
+static bool
 dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
 {
        raw_spin_rq_unlock_irq(rq);
        printk(KERN_ERR "bad: scheduling from the idle thread!\n");
        dump_stack();
        raw_spin_rq_lock_irq(rq);
+       return true;
 }
 
 /*

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index a8731da04cd592ef98bcded28507e111f0e47de5..fdc8e059cab0cb25b06a8f6dd96c088768849cf2 100644 (file)
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1483,7 +1483,7 @@ enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)
                enqueue_pushable_task(rq, p);
 }
 
-static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
+static bool dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
 {
        struct sched_rt_entity *rt_se = &p->rt;
 
@@ -1491,6 +1491,8 @@ static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
        dequeue_rt_entity(rt_se, flags);
 
        dequeue_pushable_task(rq, p);
+
+       return true;
 }
 
 /*

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index a6d6b6f106dacf65f16abc37a5eceb54c50221d4..6196f90df93e18cafb02ebd471b358ff5087345e 100644 (file)
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2285,7 +2285,7 @@ struct sched_class {
 #endif
 
        void (*enqueue_task) (struct rq *rq, struct task_struct *p, int flags);
-       void (*dequeue_task) (struct rq *rq, struct task_struct *p, int flags);
+       bool (*dequeue_task) (struct rq *rq, struct task_struct *p, int flags);
        void (*yield_task)   (struct rq *rq);
        bool (*yield_to_task)(struct rq *rq, struct task_struct *p);
 
@@ -3606,7 +3606,7 @@ extern int __sched_setaffinity(struct task_struct *p, struct affinity_context *c
 extern void __setscheduler_prio(struct task_struct *p, int prio);
 extern void set_load_weight(struct task_struct *p, bool update_load);
 extern void enqueue_task(struct rq *rq, struct task_struct *p, int flags);
-extern void dequeue_task(struct rq *rq, struct task_struct *p, int flags);
+extern bool dequeue_task(struct rq *rq, struct task_struct *p, int flags);
 
 extern void check_class_changed(struct rq *rq, struct task_struct *p,
                                const struct sched_class *prev_class,

diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c
index b1b8fe61c532a118aa58c84eb9cbf3ba014d74ed..4cf02074fa9e581817c880fda6e914cb1994fe17 100644 (file)
--- a/kernel/sched/stop_task.c
+++ b/kernel/sched/stop_task.c
@@ -57,10 +57,11 @@ enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
        add_nr_running(rq, 1);
 }
 
-static void
+static bool
 dequeue_task_stop(struct rq *rq, struct task_struct *p, int flags)
 {
        sub_nr_running(rq, 1);
+       return true;
 }
 
 static void yield_task_stop(struct rq *rq)