From 79bd233010859463e46a0a4b3926eaaba25a6110 Mon Sep 17 00:00:00 2001 From: Ben Gainey Date: Tue, 30 Jul 2024 09:44:14 +0100 Subject: [PATCH] perf: Rename perf_event_context.nr_pending to nr_no_switch_fast. nr_pending counts the number of events in the context that either pending_sigtrap or pending_work, but it is used to prevent taking the fast path in perf_event_context_sched_out. Renamed to reflect what it is used for, rather than what it counts. This change allows using the field to track other event properties that also require skipping the fast path without possible confusion over the name. Signed-off-by: Ben Gainey Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20240730084417.7693-2-ben.gainey@arm.com --- include/linux/perf_event.h | 5 +++-- kernel/events/core.c | 12 ++++++------ 2 files changed, 9 insertions(+), 8 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 6bb0c21d6335b..655f66b18418a 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -966,12 +966,13 @@ struct perf_event_context { struct rcu_head rcu_head; /* - * Sum (event->pending_work + event->pending_work) + * The count of events for which using the switch-out fast path + * should be avoided. * * The SIGTRAP is targeted at ctx->task, as such it won't do changing * that until the signal is delivered. */ - local_t nr_pending; + local_t nr_no_switch_fast; }; struct perf_cpu_pmu_context { diff --git a/kernel/events/core.c b/kernel/events/core.c index aa3450bdc2276..e6cc354a3ceef 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3516,9 +3516,9 @@ perf_event_context_sched_out(struct task_struct *task, struct task_struct *next) perf_ctx_disable(ctx, false); - /* PMIs are disabled; ctx->nr_pending is stable. */ - if (local_read(&ctx->nr_pending) || - local_read(&next_ctx->nr_pending)) { + /* PMIs are disabled; ctx->nr_no_switch_fast is stable. */ + if (local_read(&ctx->nr_no_switch_fast) || + local_read(&next_ctx->nr_no_switch_fast)) { /* * Must not swap out ctx when there's pending * events that rely on the ctx->task relation. @@ -5204,7 +5204,7 @@ static void perf_pending_task_sync(struct perf_event *event) */ if (task_work_cancel(current, head)) { event->pending_work = 0; - local_dec(&event->ctx->nr_pending); + local_dec(&event->ctx->nr_no_switch_fast); return; } @@ -6868,7 +6868,7 @@ static void perf_pending_task(struct callback_head *head) if (event->pending_work) { event->pending_work = 0; perf_sigtrap(event); - local_dec(&event->ctx->nr_pending); + local_dec(&event->ctx->nr_no_switch_fast); rcuwait_wake_up(&event->pending_work_wait); } rcu_read_unlock(); @@ -9740,7 +9740,7 @@ static int __perf_event_overflow(struct perf_event *event, if (!event->pending_work && !task_work_add(current, &event->pending_task, notify_mode)) { event->pending_work = pending_id; - local_inc(&event->ctx->nr_pending); + local_inc(&event->ctx->nr_no_switch_fast); event->pending_addr = 0; if (valid_sample && (data->sample_flags & PERF_SAMPLE_ADDR))