Commit 8ed28dec authored by Keisuke Nishimura's avatar Keisuke Nishimura Committed by Wenyu Huang
Browse files

sched/fair: Take the scheduling domain into account in select_idle_smt() 

stable inclusion
from stable-v6.6.23
commit 495b7cb952003973ff1fe4f70639bf3df91fbfb1
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IB2B23

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-6.6.y&id=495b7cb952003973ff1fe4f70639bf3df91fbfb1



--------------------------------

[ Upstream commit 8aeaffef8c6eceab0e1498486fdd4f3dc3b7066c ]

When picking a CPU on task wakeup, select_idle_smt() has to take
into account the scheduling domain of @target. This is because the
"isolcpus" kernel command line option can remove CPUs from the domain to
isolate them from other SMT siblings.

This fix checks if the candidate CPU is in the target scheduling domain.

Commit:

  df3cb4ea ("sched/fair: Fix wrong cpu selecting from isolated domain")

... originally introduced this fix by adding the check of the scheduling
domain in the loop.

However, commit:

  3e6efe87 ("sched/fair: Remove redundant check in select_idle_smt()")

... accidentally removed the check. Bring it back.

Fixes: 3e6efe87 ("sched/fair: Remove redundant check in select_idle_smt()")
Signed-off-by: default avatarKeisuke Nishimura <keisuke.nishimura@inria.fr>
Signed-off-by: default avatarJulia Lawall <julia.lawall@inria.fr>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Reviewed-by: default avatarVincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20240110131707.437301-1-keisuke.nishimura@inria.fr


Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
Signed-off-by: default avatarWenyu Huang <huangwenyu5@huawei.com>
parent ca3d9e6a

kernel/sched/fair.c

+9 −3
Original line number Diff line number Diff line
@@ -8070,7 +8070,7 @@ static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpu 
/*

 * Scan the local SMT mask for idle CPUs.

 */

static int select_idle_smt(struct task_struct *p, int target)

static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)

{

	int cpu;
@@ -8081,6 +8081,12 @@ static int select_idle_smt(struct task_struct *p, int target) 
#endif

		if (cpu == target)

			continue;

		/*

		 * Check if the CPU is in the LLC scheduling domain of @target.

		 * Due to isolcpus, there is no guarantee that all the siblings are in the domain.

		 */

		if (!cpumask_test_cpu(cpu, sched_domain_span(sd)))

			continue;

		if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))

			return cpu;

	}
@@ -8104,7 +8110,7 @@ static inline int select_idle_core(struct task_struct *p, int core, struct cpuma 
	return __select_idle_cpu(core, p);

}



static inline int select_idle_smt(struct task_struct *p, int target)

static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)

{

	return -1;

}
@@ -8441,7 +8447,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target) 
		has_idle_core = test_idle_cores(target);



		if (!has_idle_core && cpus_share_cache(prev, target)) {

			i = select_idle_smt(p, prev);

			i = select_idle_smt(p, sd, prev);

			if ((unsigned int)i < nr_cpumask_bits)

				return i;

		}