niansa-misc/linux
1
0
Fork 0
mirror of synced 2025-03-06 20:59:54 +01:00
Code Issues Projects Releases Packages Wiki Activity

sched_ext: Use task_can_run_on_remote_rq() test in dispatch_to_local_dsq()

Browse source 
When deciding whether a task can be migrated to a CPU,
dispatch_to_local_dsq() was open-coding p->cpus_allowed and scx_rq_online()
tests instead of using task_can_run_on_remote_rq(). This had two problems.

- It was missing is_migration_disabled() check and thus could try to migrate
  a task which shouldn't leading to assertion and scheduling failures.

- It was testing p->cpus_ptr directly instead of using task_allowed_on_cpu()
  and thus failed to consider ISA compatibility.

Update dispatch_to_local_dsq() to use task_can_run_on_remote_rq():

- Move scx_ops_error() triggering into task_can_run_on_remote_rq().

- When migration isn't allowed, fall back to the global DSQ instead of the
  source DSQ by returning DTL_INVALID. This is both simpler and an overall
  better behavior.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Acked-by: David Vernet <void@manifault.com>
This commit is contained in:
Tejun Heo 2024-08-30 00:51:40 -10:00
parent bf934bed5e
commit 0366017e09
1 changed files with 20 additions and 20 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

40
kernel/sched/ext.c
View file

@ -2203,16 +2203,30 @@ static void consume_local_task(struct rq *rq, struct scx_dispatch_q *dsq,
* - The BPF scheduler is bypassed while the rq is offline and we can always say
* no to the BPF scheduler initiated migrations while offline.
*/
static bool task_can_run_on_remote_rq(struct task_struct *p, struct rq *rq)
static bool task_can_run_on_remote_rq(struct task_struct *p, struct rq *rq,
bool trigger_error)
{
int cpu = cpu_of(rq);
if (!task_allowed_on_cpu(p, cpu))
/*
* We don't require the BPF scheduler to avoid dispatching to offline
* CPUs mostly for convenience but also because CPUs can go offline
* between scx_bpf_dispatch() calls and here. Trigger error iff the
* picked CPU is outside the allowed mask.
*/
if (!task_allowed_on_cpu(p, cpu)) {
if (trigger_error)
scx_ops_error("SCX_DSQ_LOCAL[_ON] verdict target cpu %d not allowed for %s[%d]",
cpu_of(rq), p->comm, p->pid);
return false;
}
if (unlikely(is_migration_disabled(p)))
return false;
if (!scx_rq_online(rq))
return false;
return true;
}
@ -2240,9 +2254,8 @@ static bool consume_remote_task(struct rq *rq, struct scx_dispatch_q *dsq,
return move_task_to_local_dsq(p, 0, task_rq, rq);
}
#else /* CONFIG_SMP */
static bool task_can_run_on_remote_rq(struct task_struct *p, struct rq *rq) { return false; }
static bool consume_remote_task(struct rq *rq, struct scx_dispatch_q *dsq,
struct task_struct *p, struct rq *task_rq) { return false; }
static inline bool task_can_run_on_remote_rq(struct task_struct *p, struct rq *rq, bool trigger_error) { return false; }
static inline bool consume_remote_task(struct rq *rq, struct scx_dispatch_q *dsq, struct task_struct *p, struct rq *task_rq) { return false; }
#endif /* CONFIG_SMP */
static bool consume_dispatch_q(struct rq *rq, struct scx_dispatch_q *dsq)
@ -2267,7 +2280,7 @@ retry:
return true;
}
if (task_can_run_on_remote_rq(p, rq)) {
if (task_can_run_on_remote_rq(p, rq, false)) {
if (likely(consume_remote_task(rq, dsq, p, task_rq)))
return true;
goto retry;
@ -2330,7 +2343,7 @@ dispatch_to_local_dsq(struct rq *rq, u64 dsq_id, struct task_struct *p,
}
#ifdef CONFIG_SMP
if (cpumask_test_cpu(cpu_of(dst_rq), p->cpus_ptr)) {
if (likely(task_can_run_on_remote_rq(p, dst_rq, true))) {
bool dsp;
/*
@ -2355,17 +2368,6 @@ dispatch_to_local_dsq(struct rq *rq, u64 dsq_id, struct task_struct *p,
raw_spin_rq_lock(src_rq);
}
/*
* We don't require the BPF scheduler to avoid dispatching to
* offline CPUs mostly for convenience but also because CPUs can
* go offline between scx_bpf_dispatch() calls and here. If @p
* is destined to an offline CPU, queue it on its current CPU
* instead, which should always be safe. As this is an allowed
* behavior, don't trigger an ops error.
*/
if (!scx_rq_online(dst_rq))
dst_rq = src_rq;
if (src_rq == dst_rq) {
/*
* As @p is staying on the same rq, there's no need to
@ -2399,8 +2401,6 @@ dispatch_to_local_dsq(struct rq *rq, u64 dsq_id, struct task_struct *p,
}
#endif /* CONFIG_SMP */
scx_ops_error("SCX_DSQ_LOCAL[_ON] verdict target cpu %d not allowed for %s[%d]",
cpu_of(dst_rq), p->comm, p->pid);
return DTL_INVALID;
}