diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/core.c | 126 | ||||
| -rw-r--r-- | kernel/sched/membarrier.c | 4 |
2 files changed, 63 insertions, 67 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index ca2bb629595f..98191218d891 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1862,8 +1862,13 @@ struct migration_arg { struct set_affinity_pending *pending; }; +/* + * @refs: number of wait_for_completion() + * @stop_pending: is @stop_work in use + */ struct set_affinity_pending { refcount_t refs; + unsigned int stop_pending; struct completion done; struct cpu_stop_work stop_work; struct migration_arg arg; @@ -1898,8 +1903,8 @@ static struct rq *__migrate_task(struct rq *rq, struct rq_flags *rf, */ static int migration_cpu_stop(void *data) { - struct set_affinity_pending *pending; struct migration_arg *arg = data; + struct set_affinity_pending *pending = arg->pending; struct task_struct *p = arg->task; int dest_cpu = arg->dest_cpu; struct rq *rq = this_rq(); @@ -1921,7 +1926,6 @@ static int migration_cpu_stop(void *data) raw_spin_lock(&p->pi_lock); rq_lock(rq, &rf); - 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 @@ -1932,21 +1936,14 @@ static int migration_cpu_stop(void *data) goto out; if (pending) { - p->migration_pending = NULL; + if (p->migration_pending == pending) + p->migration_pending = NULL; complete = true; } - /* migrate_enable() -- we must not race against SCA */ if (dest_cpu < 0) { - /* - * When this was migrate_enable() but we no longer - * have a @pending, a concurrent SCA 'fixed' things - * and we should be valid again. Nothing to do. - */ - if (!pending) { - WARN_ON_ONCE(!cpumask_test_cpu(task_cpu(p), &p->cpus_mask)); + if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask)) goto out; - } dest_cpu = cpumask_any_distribute(&p->cpus_mask); } @@ -1956,7 +1953,14 @@ static int migration_cpu_stop(void *data) else p->wake_cpu = dest_cpu; - } else if (dest_cpu < 0 || pending) { + /* + * XXX __migrate_task() can fail, at which point we might end + * up running on a dodgy CPU, AFAICT this can only happen + * during CPU hotplug, at which point we'll get pushed out + * anyway, so it's probably not a big deal. + */ + + } else if (pending) { /* * This happens when we get migrated between migrate_enable()'s * preempt_enable() and scheduling the stopper task. At that @@ -1971,43 +1975,32 @@ static int migration_cpu_stop(void *data) * ->pi_lock, so the allowed mask is stable - if it got * somewhere allowed, we're done. */ - if (pending && cpumask_test_cpu(task_cpu(p), p->cpus_ptr)) { - p->migration_pending = NULL; + if (cpumask_test_cpu(task_cpu(p), p->cpus_ptr)) { + if (p->migration_pending == pending) + p->migration_pending = NULL; complete = true; goto out; } /* - * When this was migrate_enable() but we no longer have an - * @pending, a concurrent SCA 'fixed' things and we should be - * valid again. Nothing to do. - */ - if (!pending) { - WARN_ON_ONCE(!cpumask_test_cpu(task_cpu(p), &p->cpus_mask)); - goto out; - } - - /* * When migrate_enable() hits a rq mis-match we can't reliably * determine is_migration_disabled() and so have to chase after * it. */ + WARN_ON_ONCE(!pending->stop_pending); task_rq_unlock(rq, p, &rf); stop_one_cpu_nowait(task_cpu(p), migration_cpu_stop, &pending->arg, &pending->stop_work); return 0; } out: + if (pending) + pending->stop_pending = false; task_rq_unlock(rq, p, &rf); if (complete) complete_all(&pending->done); - /* For pending->{arg,stop_work} */ - pending = arg->pending; - if (pending && refcount_dec_and_test(&pending->refs)) - wake_up_var(&pending->refs); - return 0; } @@ -2194,11 +2187,7 @@ static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flag int dest_cpu, unsigned int flags) { struct set_affinity_pending my_pending = { }, *pending = NULL; - struct migration_arg arg = { - .task = p, - .dest_cpu = dest_cpu, - }; - bool complete = false; + bool stop_pending, complete = false; /* Can the task run on the task's current CPU? If so, we're done */ if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask)) { @@ -2210,12 +2199,16 @@ static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flag push_task = get_task_struct(p); } + /* + * If there are pending waiters, but no pending stop_work, + * then complete now. + */ pending = p->migration_pending; - if (pending) { - refcount_inc(&pending->refs); + if (pending && !pending->stop_pending) { p->migration_pending = NULL; complete = true; } + task_rq_unlock(rq, p, rf); if (push_task) { @@ -2224,7 +2217,7 @@ static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flag } if (complete) - goto do_complete; + complete_all(&pending->done); return 0; } @@ -2235,6 +2228,12 @@ static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flag /* Install the request */ refcount_set(&my_pending.refs, 1); init_completion(&my_pending.done); + my_pending.arg = (struct migration_arg) { + .task = p, + .dest_cpu = -1, /* any */ + .pending = &my_pending, + }; + p->migration_pending = &my_pending; } else { pending = p->migration_pending; @@ -2259,45 +2258,41 @@ static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flag return -EINVAL; } - if (flags & SCA_MIGRATE_ENABLE) { - - refcount_inc(&pending->refs); /* pending->{arg,stop_work} */ - p->migration_flags &= ~MDF_PUSH; - task_rq_unlock(rq, p, rf); - - pending->arg = (struct migration_arg) { - .task = p, - .dest_cpu = -1, - .pending = pending, - }; - - stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop, - &pending->arg, &pending->stop_work); - - return 0; - } - if (task_running(rq, p) || p->state == TASK_WAKING) { /* - * Lessen races (and headaches) by delegating - * is_migration_disabled(p) checks to the stopper, which will - * run on the same CPU as said p. + * MIGRATE_ENABLE gets here because 'p == current', but for + * anything else we cannot do is_migration_disabled(), punt + * and have the stopper function handle it all race-free. */ + stop_pending = pending->stop_pending; + if (!stop_pending) + pending->stop_pending = true; + + if (flags & SCA_MIGRATE_ENABLE) + p->migration_flags &= ~MDF_PUSH; + task_rq_unlock(rq, p, rf); - stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg); + if (!stop_pending) { + stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop, + &pending->arg, &pending->stop_work); + } + + if (flags & SCA_MIGRATE_ENABLE) + return 0; } else { if (!is_migration_disabled(p)) { if (task_on_rq_queued(p)) rq = move_queued_task(rq, rf, p, dest_cpu); - p->migration_pending = NULL; - complete = true; + if (!pending->stop_pending) { + p->migration_pending = NULL; + complete = true; + } } task_rq_unlock(rq, p, rf); -do_complete: if (complete) complete_all(&pending->done); } @@ -2305,7 +2300,7 @@ do_complete: wait_for_completion(&pending->done); if (refcount_dec_and_test(&pending->refs)) - wake_up_var(&pending->refs); + wake_up_var(&pending->refs); /* No UaF, just an address */ /* * Block the original owner of &pending until all subsequent callers @@ -2313,6 +2308,9 @@ do_complete: */ wait_var_event(&my_pending.refs, !refcount_read(&my_pending.refs)); + /* ARGH */ + WARN_ON_ONCE(my_pending.stop_pending); + return 0; } diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c index acdae625c636..b5add64d9698 100644 --- a/kernel/sched/membarrier.c +++ b/kernel/sched/membarrier.c @@ -471,9 +471,7 @@ static int sync_runqueues_membarrier_state(struct mm_struct *mm) } rcu_read_unlock(); - preempt_disable(); - smp_call_function_many(tmpmask, ipi_sync_rq_state, mm, 1); - preempt_enable(); + on_each_cpu_mask(tmpmask, ipi_sync_rq_state, mm, true); free_cpumask_var(tmpmask); cpus_read_unlock(); |