From: Scott Wood Date: Sat, 12 Oct 2019 01:52:14 -0500 Subject: [PATCH 308/351] sched: migrate_enable: Use stop_one_cpu_nowait() Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=1c8f8380a7031358ac5fc4177bbbe5d03bc6cfd2 [ Upstream commit 6b39a1fa8c53cae08dc03afdae193b7d3a78a173 ] migrate_enable() can be called with current->state != TASK_RUNNING. Avoid clobbering the existing state by using stop_one_cpu_nowait(). Since we're stopping the current cpu, we know that we won't get past __schedule() until migration_cpu_stop() has run (at least up to the point of migrating us to another cpu). Signed-off-by: Scott Wood Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Steven Rostedt (VMware) --- include/linux/stop_machine.h | 2 ++ kernel/sched/core.c | 23 +++++++++++++---------- kernel/stop_machine.c | 7 +++++-- 3 files changed, 20 insertions(+), 12 deletions(-) diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h index ccdaa8fd5657..150e886ed83d 100644 --- a/include/linux/stop_machine.h +++ b/include/linux/stop_machine.h @@ -26,6 +26,8 @@ struct cpu_stop_work { cpu_stop_fn_t fn; void *arg; struct cpu_stop_done *done; + /* Did not run due to disabled stopper; for nowait debug checks */ + bool disabled; }; int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index a2c0f199f362..eeb53ea1483c 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -990,6 +990,7 @@ static struct rq *move_queued_task(struct rq *rq, struct rq_flags *rf, struct migration_arg { struct task_struct *task; int dest_cpu; + bool done; }; /* @@ -1025,6 +1026,11 @@ static int migration_cpu_stop(void *data) struct task_struct *p = arg->task; struct rq *rq = this_rq(); struct rq_flags rf; + int dest_cpu = arg->dest_cpu; + + /* We don't look at arg after this point. */ + smp_mb(); + arg->done = true; /* * The original target CPU might have gone down and we might @@ -1047,9 +1053,9 @@ static int migration_cpu_stop(void *data) */ if (task_rq(p) == rq) { if (task_on_rq_queued(p)) - rq = __migrate_task(rq, &rf, p, arg->dest_cpu); + rq = __migrate_task(rq, &rf, p, dest_cpu); else - p->wake_cpu = arg->dest_cpu; + p->wake_cpu = dest_cpu; } rq_unlock(rq, &rf); raw_spin_unlock(&p->pi_lock); @@ -7317,6 +7323,7 @@ void migrate_enable(void) WARN_ON(smp_processor_id() != cpu); if (!is_cpu_allowed(p, cpu)) { struct migration_arg arg = { p }; + struct cpu_stop_work work; struct rq_flags rf; rq = task_rq_lock(p, &rf); @@ -7324,15 +7331,11 @@ void migrate_enable(void) arg.dest_cpu = select_fallback_rq(cpu, p); task_rq_unlock(rq, p, &rf); - preempt_lazy_enable(); - preempt_enable(); - - sleeping_lock_inc(); - stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg); - sleeping_lock_dec(); + stop_one_cpu_nowait(task_cpu(p), migration_cpu_stop, + &arg, &work); tlb_migrate_finish(p->mm); - - return; + __schedule(true); + WARN_ON_ONCE(!arg.done && !work.disabled); } out: diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index 067cb83f37ea..2d15c0d50625 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -86,8 +86,11 @@ static bool cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work) enabled = stopper->enabled; if (enabled) __cpu_stop_queue_work(stopper, work, &wakeq); - else if (work->done) - cpu_stop_signal_done(work->done); + else { + work->disabled = true; + if (work->done) + cpu_stop_signal_done(work->done); + } raw_spin_unlock_irqrestore(&stopper->lock, flags); wake_up_q(&wakeq);