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sched_ext: Fixes for v6.19-rc1 

- Fix memory leak when destroying helper kthread workers during scheduler
   disable.
 
 - Fix bypass depth accounting on scx_enable() failure which could leave
   the system permanently in bypass mode.
 
 - Fix missing preemption handling when moving tasks to local DSQs via
   scx_bpf_dsq_move().
 
 - Misc fixes including NULL check for put_prev_task(), flushing stdout in
   selftests, and removing unused code.
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Merge tag 'sched_ext-for-6.19-rc1-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext

Pull sched_ext fixes from Tejun Heo:

 - Fix memory leak when destroying helper kthread workers during
   scheduler disable

 - Fix bypass depth accounting on scx_enable() failure which could leave
   the system permanently in bypass mode

 - Fix missing preemption handling when moving tasks to local DSQs via
   scx_bpf_dsq_move()

 - Misc fixes including NULL check for put_prev_task(), flushing stdout
   in selftests, and removing unused code

* tag 'sched_ext-for-6.19-rc1-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
  sched_ext: Remove unused code in the do_pick_task_scx()
  selftests/sched_ext: flush stdout before test to avoid log spam
  sched_ext: Fix missing post-enqueue handling in move_local_task_to_local_dsq()
  sched_ext: Factor out local_dsq_post_enq() from dispatch_enqueue()
  sched_ext: Fix bypass depth leak on scx_enable() failure
  sched/ext: Avoid null ptr traversal when ->put_prev_task() is called with NULL next
  sched_ext: Fix the memleak for sch->helper objects
master
Linus Torvalds 2025-12-16 19:24:35 +12:00
parent 6b63f90fa2 bb27226f0d
commit dbf89321bf
2 changed files with 56 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

72
kernel/sched/ext.c
View File

@ -41,6 +41,13 @@ static bool scx_init_task_enabled;
static bool scx_switching_all;
DEFINE_STATIC_KEY_FALSE(__scx_switched_all);
/*
* Tracks whether scx_enable() called scx_bypass(true). Used to balance bypass
* depth on enable failure. Will be removed when bypass depth is moved into the
* sched instance.
*/
static bool scx_bypassed_for_enable;
static atomic_long_t scx_nr_rejected = ATOMIC_LONG_INIT(0);
static atomic_long_t scx_hotplug_seq = ATOMIC_LONG_INIT(0);
@ -975,6 +982,30 @@ static void refill_task_slice_dfl(struct scx_sched *sch, struct task_struct *p)
__scx_add_event(sch, SCX_EV_REFILL_SLICE_DFL, 1);
}
static void local_dsq_post_enq(struct scx_dispatch_q *dsq, struct task_struct *p,
u64 enq_flags)
{
struct rq *rq = container_of(dsq, struct rq, scx.local_dsq);
bool preempt = false;
/*
* If @rq is in balance, the CPU is already vacant and looking for the
* next task to run. No need to preempt or trigger resched after moving
* @p into its local DSQ.
*/
if (rq->scx.flags & SCX_RQ_IN_BALANCE)
return;
if ((enq_flags & SCX_ENQ_PREEMPT) && p != rq->curr &&
rq->curr->sched_class == &ext_sched_class) {
rq->curr->scx.slice = 0;
preempt = true;
}
if (preempt || sched_class_above(&ext_sched_class, rq->curr->sched_class))
resched_curr(rq);
}
static void dispatch_enqueue(struct scx_sched *sch, struct scx_dispatch_q *dsq,
struct task_struct *p, u64 enq_flags)
{
@ -1086,23 +1117,11 @@ static void dispatch_enqueue(struct scx_sched *sch, struct scx_dispatch_q *dsq,
if (enq_flags & SCX_ENQ_CLEAR_OPSS)
atomic_long_set_release(&p->scx.ops_state, SCX_OPSS_NONE);
if (is_local) {
struct rq *rq = container_of(dsq, struct rq, scx.local_dsq);
bool preempt = false;
if ((enq_flags & SCX_ENQ_PREEMPT) && p != rq->curr &&
rq->curr->sched_class == &ext_sched_class) {
rq->curr->scx.slice = 0;
preempt = true;
}
if (preempt || sched_class_above(&ext_sched_class,
rq->curr->sched_class))
resched_curr(rq);
} else {
if (is_local)
local_dsq_post_enq(dsq, p, enq_flags);
else
raw_spin_unlock(&dsq->lock);
}
}
static void task_unlink_from_dsq(struct task_struct *p,
struct scx_dispatch_q *dsq)
@ -1625,6 +1644,8 @@ static void move_local_task_to_local_dsq(struct task_struct *p, u64 enq_flags,
dsq_mod_nr(dst_dsq, 1);
p->scx.dsq = dst_dsq;
local_dsq_post_enq(dst_dsq, p, enq_flags);
}
/**
@ -2402,7 +2423,7 @@ static void put_prev_task_scx(struct rq *rq, struct task_struct *p,
* ops.enqueue() that @p is the only one available for this cpu,
* which should trigger an explicit follow-up scheduling event.
*/
if (sched_class_above(&ext_sched_class, next->sched_class)) {
if (next && sched_class_above(&ext_sched_class, next->sched_class)) {
WARN_ON_ONCE(!(sch->ops.flags & SCX_OPS_ENQ_LAST));
do_enqueue_task(rq, p, SCX_ENQ_LAST, -1);
} else {
@ -2425,7 +2446,7 @@ static struct task_struct *
do_pick_task_scx(struct rq *rq, struct rq_flags *rf, bool force_scx)
{
struct task_struct *prev = rq->curr;
bool keep_prev, kick_idle = false;
bool keep_prev;
struct task_struct *p;
/* see kick_cpus_irq_workfn() */
@ -2467,12 +2488,8 @@ do_pick_task_scx(struct rq *rq, struct rq_flags *rf, bool force_scx)
refill_task_slice_dfl(rcu_dereference_sched(scx_root), p);
} else {
p = first_local_task(rq);
if (!p) {
if (kick_idle)
scx_kick_cpu(rcu_dereference_sched(scx_root),
cpu_of(rq), SCX_KICK_IDLE);
if (!p)
return NULL;
}
if (unlikely(!p->scx.slice)) {
struct scx_sched *sch = rcu_dereference_sched(scx_root);
@ -3575,7 +3592,7 @@ static void scx_sched_free_rcu_work(struct work_struct *work)
int node;
irq_work_sync(&sch->error_irq_work);
kthread_stop(sch->helper->task);
kthread_destroy_worker(sch->helper);
free_percpu(sch->pcpu);
@ -4318,6 +4335,11 @@ static void scx_disable_workfn(struct kthread_work *work)
scx_dsp_max_batch = 0;
free_kick_syncs();
if (scx_bypassed_for_enable) {
scx_bypassed_for_enable = false;
scx_bypass(false);
}
mutex_unlock(&scx_enable_mutex);
WARN_ON_ONCE(scx_set_enable_state(SCX_DISABLED) != SCX_DISABLING);
@ -4786,7 +4808,7 @@ static struct scx_sched *scx_alloc_and_add_sched(struct sched_ext_ops *ops)
return sch;
err_stop_helper:
kthread_stop(sch->helper->task);
kthread_destroy_worker(sch->helper);
err_free_pcpu:
free_percpu(sch->pcpu);
err_free_gdsqs:
@ -4970,6 +4992,7 @@ static int scx_enable(struct sched_ext_ops *ops, struct bpf_link *link)
* Init in bypass mode to guarantee forward progress.
*/
scx_bypass(true);
scx_bypassed_for_enable = true;
for (i = SCX_OPI_NORMAL_BEGIN; i < SCX_OPI_NORMAL_END; i++)
if (((void (**)(void))ops)[i])
@ -5067,6 +5090,7 @@ static int scx_enable(struct sched_ext_ops *ops, struct bpf_link *link)
scx_task_iter_stop(&sti);
percpu_up_write(&scx_fork_rwsem);
scx_bypassed_for_enable = false;
scx_bypass(false);
if (!scx_tryset_enable_state(SCX_ENABLED, SCX_ENABLING)) {

8
tools/testing/selftests/sched_ext/runner.c
View File

@ -46,6 +46,14 @@ static void print_test_preamble(const struct scx_test *test, bool quiet)
if (!quiet)
printf("DESCRIPTION: %s\n", test->description);
printf("OUTPUT:\n");
/*
* The tests may fork with the preamble buffered
* in the children's stdout. Flush before the test
* to avoid printing the message multiple times.
*/
fflush(stdout);
fflush(stderr);
}
static const char *status_to_result(enum scx_test_status status)