diff options
Diffstat (limited to 'kernel/events')
| -rw-r--r-- | kernel/events/core.c | 74 | ||||
| -rw-r--r-- | kernel/events/uprobes.c | 15 |
2 files changed, 36 insertions, 53 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index 128db74e9eab..95e703891b24 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3943,7 +3943,7 @@ static int merge_sched_in(struct perf_event *event, void *data) perf_event_set_state(event, PERF_EVENT_STATE_ERROR); if (*perf_event_fasync(event)) - event->pending_kill = POLL_HUP; + event->pending_kill = POLL_ERR; perf_event_wakeup(event); } else { @@ -5518,30 +5518,6 @@ static bool exclusive_event_installable(struct perf_event *event, static void perf_free_addr_filters(struct perf_event *event); -static void perf_pending_task_sync(struct perf_event *event) -{ - struct callback_head *head = &event->pending_task; - - if (!event->pending_work) - return; - /* - * If the task is queued to the current task's queue, we - * obviously can't wait for it to complete. Simply cancel it. - */ - if (task_work_cancel(current, head)) { - event->pending_work = 0; - local_dec(&event->ctx->nr_no_switch_fast); - return; - } - - /* - * All accesses related to the event are within the same RCU section in - * perf_pending_task(). The RCU grace period before the event is freed - * will make sure all those accesses are complete by then. - */ - rcuwait_wait_event(&event->pending_work_wait, !event->pending_work, TASK_UNINTERRUPTIBLE); -} - /* vs perf_event_alloc() error */ static void __free_event(struct perf_event *event) { @@ -5599,7 +5575,6 @@ static void _free_event(struct perf_event *event) { irq_work_sync(&event->pending_irq); irq_work_sync(&event->pending_disable_irq); - perf_pending_task_sync(event); unaccount_event(event); @@ -5692,10 +5667,17 @@ static void perf_remove_from_owner(struct perf_event *event) static void put_event(struct perf_event *event) { + struct perf_event *parent; + if (!atomic_long_dec_and_test(&event->refcount)) return; + parent = event->parent; _free_event(event); + + /* Matches the refcount bump in inherit_event() */ + if (parent) + put_event(parent); } /* @@ -5779,11 +5761,6 @@ again: if (tmp == child) { perf_remove_from_context(child, DETACH_GROUP); list_move(&child->child_list, &free_list); - /* - * This matches the refcount bump in inherit_event(); - * this can't be the last reference. - */ - put_event(event); } else { var = &ctx->refcount; } @@ -5809,7 +5786,8 @@ again: void *var = &child->ctx->refcount; list_del(&child->child_list); - free_event(child); + /* Last reference unless ->pending_task work is pending */ + put_event(child); /* * Wake any perf_event_free_task() waiting for this event to be @@ -5820,7 +5798,11 @@ again: } no_ctx: - put_event(event); /* Must be the 'last' reference */ + /* + * Last reference unless ->pending_task work is pending on this event + * or any of its children. + */ + put_event(event); return 0; } EXPORT_SYMBOL_GPL(perf_event_release_kernel); @@ -6093,7 +6075,7 @@ static __poll_t perf_poll(struct file *file, poll_table *wait) if (unlikely(READ_ONCE(event->state) == PERF_EVENT_STATE_ERROR && event->attr.pinned)) - return events; + return EPOLLERR; /* * Pin the event->rb by taking event->mmap_mutex; otherwise @@ -7236,12 +7218,6 @@ static void perf_pending_task(struct callback_head *head) int rctx; /* - * All accesses to the event must belong to the same implicit RCU read-side - * critical section as the ->pending_work reset. See comment in - * perf_pending_task_sync(). - */ - rcu_read_lock(); - /* * If we 'fail' here, that's OK, it means recursion is already disabled * and we won't recurse 'further'. */ @@ -7251,9 +7227,8 @@ static void perf_pending_task(struct callback_head *head) event->pending_work = 0; perf_sigtrap(event); local_dec(&event->ctx->nr_no_switch_fast); - rcuwait_wake_up(&event->pending_work_wait); } - rcu_read_unlock(); + put_event(event); if (rctx >= 0) perf_swevent_put_recursion_context(rctx); @@ -10248,6 +10223,7 @@ static int __perf_event_overflow(struct perf_event *event, !task_work_add(current, &event->pending_task, notify_mode)) { event->pending_work = pending_id; local_inc(&event->ctx->nr_no_switch_fast); + WARN_ON_ONCE(!atomic_long_inc_not_zero(&event->refcount)); event->pending_addr = 0; if (valid_sample && (data->sample_flags & PERF_SAMPLE_ADDR)) @@ -12610,7 +12586,6 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu, init_irq_work(&event->pending_irq, perf_pending_irq); event->pending_disable_irq = IRQ_WORK_INIT_HARD(perf_pending_disable); init_task_work(&event->pending_task, perf_pending_task); - rcuwait_init(&event->pending_work_wait); mutex_init(&event->mmap_mutex); raw_spin_lock_init(&event->addr_filters.lock); @@ -13747,8 +13722,7 @@ perf_event_exit_event(struct perf_event *event, struct perf_event_context *ctx) * Kick perf_poll() for is_event_hup(); */ perf_event_wakeup(parent_event); - free_event(event); - put_event(parent_event); + put_event(event); return; } @@ -13872,13 +13846,11 @@ static void perf_free_event(struct perf_event *event, list_del_init(&event->child_list); mutex_unlock(&parent->child_mutex); - put_event(parent); - raw_spin_lock_irq(&ctx->lock); perf_group_detach(event); list_del_event(event, ctx); raw_spin_unlock_irq(&ctx->lock); - free_event(event); + put_event(event); } /* @@ -14016,6 +13988,9 @@ inherit_event(struct perf_event *parent_event, if (IS_ERR(child_event)) return child_event; + get_ctx(child_ctx); + child_event->ctx = child_ctx; + pmu_ctx = find_get_pmu_context(child_event->pmu, child_ctx, child_event); if (IS_ERR(pmu_ctx)) { free_event(child_event); @@ -14037,8 +14012,6 @@ inherit_event(struct perf_event *parent_event, return NULL; } - get_ctx(child_ctx); - /* * Make the child state follow the state of the parent event, * not its attr.disabled bit. We hold the parent's mutex, @@ -14059,7 +14032,6 @@ inherit_event(struct perf_event *parent_event, local64_set(&hwc->period_left, sample_period); } - child_event->ctx = child_ctx; child_event->overflow_handler = parent_event->overflow_handler; child_event->overflow_handler_context = parent_event->overflow_handler_context; diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 615b4e6d22c7..8d783b5882b6 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -1956,6 +1956,9 @@ static void free_ret_instance(struct uprobe_task *utask, * to-be-reused return instances for future uretprobes. If ri_timer() * happens to be running right now, though, we fallback to safety and * just perform RCU-delated freeing of ri. + * Admittedly, this is a rather simple use of seqcount, but it nicely + * abstracts away all the necessary memory barriers, so we use + * a well-supported kernel primitive here. */ if (raw_seqcount_try_begin(&utask->ri_seqcount, seq)) { /* immediate reuse of ri without RCU GP is OK */ @@ -2016,12 +2019,20 @@ static void ri_timer(struct timer_list *timer) /* RCU protects return_instance from freeing. */ guard(rcu)(); - write_seqcount_begin(&utask->ri_seqcount); + /* + * See free_ret_instance() for notes on seqcount use. + * We also employ raw API variants to avoid lockdep false-positive + * warning complaining about enabled preemption. The timer can only be + * invoked once for a uprobe_task. Therefore there can only be one + * writer. The reader does not require an even sequence count to make + * progress, so it is OK to remain preemptible on PREEMPT_RT. + */ + raw_write_seqcount_begin(&utask->ri_seqcount); for_each_ret_instance_rcu(ri, utask->return_instances) hprobe_expire(&ri->hprobe, false); - write_seqcount_end(&utask->ri_seqcount); + raw_write_seqcount_end(&utask->ri_seqcount); } static struct uprobe_task *alloc_utask(void) |