diff options
Diffstat (limited to 'debian/patches-rt/0006-perf-Don-t-disable-preemption-in-perf_pending_task.patch')
| -rw-r--r-- | debian/patches-rt/0006-perf-Don-t-disable-preemption-in-perf_pending_task.patch | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/debian/patches-rt/0006-perf-Don-t-disable-preemption-in-perf_pending_task.patch b/debian/patches-rt/0006-perf-Don-t-disable-preemption-in-perf_pending_task.patch new file mode 100644 index 0000000000..d3408aee48 --- /dev/null +++ b/debian/patches-rt/0006-perf-Don-t-disable-preemption-in-perf_pending_task.patch @@ -0,0 +1,60 @@ +From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Date: Thu, 4 Jul 2024 19:03:40 +0200 +Subject: [PATCH 6/7] perf: Don't disable preemption in perf_pending_task(). +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.10/older/patches-6.10.2-rt14.tar.xz + +perf_pending_task() is invoked in task context and disables preemption +because perf_swevent_get_recursion_context() used to access per-CPU +variables. The other reason is to create a RCU read section while +accessing the perf_event. + +The recursion counter is no longer a per-CPU accounter so disabling +preemption is no longer required. The RCU section is needed and must be +created explicit. + +Replace the preemption-disable section with a explicit RCU-read section. + +Tested-by: Marco Elver <elver@google.com> +Link: https://lore.kernel.org/r/20240704170424.1466941-7-bigeasy@linutronix.de +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + kernel/events/core.c | 11 +++++------ + 1 file changed, 5 insertions(+), 6 deletions(-) + +--- a/kernel/events/core.c ++++ b/kernel/events/core.c +@@ -5208,10 +5208,9 @@ static void perf_pending_task_sync(struc + } + + /* +- * All accesses related to the event are within the same +- * non-preemptible section in perf_pending_task(). The RCU +- * grace period before the event is freed will make sure all +- * those accesses are complete by then. ++ * 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); + } +@@ -6842,7 +6841,7 @@ static void perf_pending_task(struct cal + * critical section as the ->pending_work reset. See comment in + * perf_pending_task_sync(). + */ +- preempt_disable_notrace(); ++ rcu_read_lock(); + /* + * If we 'fail' here, that's OK, it means recursion is already disabled + * and we won't recurse 'further'. +@@ -6855,10 +6854,10 @@ static void perf_pending_task(struct cal + local_dec(&event->ctx->nr_pending); + rcuwait_wake_up(&event->pending_work_wait); + } ++ rcu_read_unlock(); + + if (rctx >= 0) + perf_swevent_put_recursion_context(rctx); +- preempt_enable_notrace(); + } + + #ifdef CONFIG_GUEST_PERF_EVENTS |