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| author | Valentin Schneider <valentin.schneider@arm.com> | 2021-02-25 10:22:30 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2021-03-06 12:40:21 +0100 |
| commit | e140749c9f194d65f5984a5941e46758377c93c0 (patch) | |
| tree | 824a915f4296e6a358eaf14fd1957c27fb909818 /kernel | |
| parent | ce29ddc47b91f97e7f69a0fb7cbb5845f52a9825 (diff) | |
| download | linux-e140749c9f194d65f5984a5941e46758377c93c0.tar.gz linux-e140749c9f194d65f5984a5941e46758377c93c0.tar.bz2 linux-e140749c9f194d65f5984a5941e46758377c93c0.zip | |
sched: Simplify migration_cpu_stop()
Since, when ->stop_pending, only the stopper can uninstall
p->migration_pending. This could simplify a few ifs, because:
(pending != NULL) => (pending == p->migration_pending)
Also, the fatty comment above affine_move_task() probably needs a bit
of gardening.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/core.c | 27 |
1 files changed, 18 insertions, 9 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 98191218d891..f9dfb349146e 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1927,6 +1927,12 @@ static int migration_cpu_stop(void *data) rq_lock(rq, &rf); /* + * If we were passed a pending, then ->stop_pending was set, thus + * p->migration_pending must have remained stable. + */ + WARN_ON_ONCE(pending && pending != p->migration_pending); + + /* * If task_rq(p) != rq, it cannot be migrated here, because we're * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because * we're holding p->pi_lock. @@ -1936,8 +1942,7 @@ static int migration_cpu_stop(void *data) goto out; if (pending) { - if (p->migration_pending == pending) - p->migration_pending = NULL; + p->migration_pending = NULL; complete = true; } @@ -1976,8 +1981,7 @@ static int migration_cpu_stop(void *data) * somewhere allowed, we're done. */ if (cpumask_test_cpu(task_cpu(p), p->cpus_ptr)) { - if (p->migration_pending == pending) - p->migration_pending = NULL; + p->migration_pending = NULL; complete = true; goto out; } @@ -2165,16 +2169,21 @@ void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask) * * (1) In the cases covered above. There is one more where the completion is * signaled within affine_move_task() itself: when a subsequent affinity request - * cancels the need for an active migration. Consider: + * occurs after the stopper bailed out due to the targeted task still being + * Migrate-Disable. Consider: * * Initial conditions: P0->cpus_mask = [0, 1] * - * P0@CPU0 P1 P2 - * - * migrate_disable(); - * <preempted> + * CPU0 P1 P2 + * <P0> + * migrate_disable(); + * <preempted> * set_cpus_allowed_ptr(P0, [1]); * <blocks> + * <migration/0> + * migration_cpu_stop() + * is_migration_disabled() + * <bails> * set_cpus_allowed_ptr(P0, [0, 1]); * <signal completion> * <awakes> |