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perf: Split __perf_pending_irq() out of perf_pending_irq()

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perf_pending_irq() invokes perf_event_wakeup() and __perf_pending_irq().
The former is in charge of waking any tasks which waits to be woken up
while the latter disables perf-events.

The irq_work perf_pending_irq(), while this an irq_work, the callback
is invoked in thread context on PREEMPT_RT. This is needed because all
the waking functions (wake_up_all(), kill_fasync()) acquire sleep locks
which must not be used with disabled interrupts.
Disabling events, as done by __perf_pending_irq(), expects a hardirq
context and disabled interrupts. This requirement is not fulfilled on
PREEMPT_RT.

Split functionality based on perf_event::pending_disable into irq_work
named `pending_disable_irq' and invoke it in hardirq context on
PREEMPT_RT. Rename the split out callback to perf_pending_disable().

Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Marco Elver <elver@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: https://lore.kernel.org/r/20240704170424.1466941-8-bigeasy@linutronix.de
This commit is contained in:
Sebastian Andrzej Siewior 2024-07-04 19:03:41 +02:00 • committed by Peter Zijlstra
parent 16b9569df9
commit 2b84def990
2 changed files with 23 additions and 7 deletions
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1
include/linux/perf_event.h
View file

@ -783,6 +783,7 @@ struct perf_event {
unsigned int pending_disable;
unsigned long pending_addr; /* SIGTRAP */
struct irq_work pending_irq;
struct irq_work pending_disable_irq;
struct callback_head pending_task;
unsigned int pending_work;
struct rcuwait pending_work_wait;

29
kernel/events/core.c
View file

@ -2451,7 +2451,7 @@ static void __perf_event_disable(struct perf_event *event,
* hold the top-level event's child_mutex, so any descendant that
* goes to exit will block in perf_event_exit_event().
*
* When called from perf_pending_irq it's OK because event->ctx
* When called from perf_pending_disable it's OK because event->ctx
* is the current context on this CPU and preemption is disabled,
* hence we can't get into perf_event_task_sched_out for this context.
*/
@ -2491,7 +2491,7 @@ EXPORT_SYMBOL_GPL(perf_event_disable);
void perf_event_disable_inatomic(struct perf_event *event)
{
event->pending_disable = 1;
irq_work_queue(&event->pending_irq);
irq_work_queue(&event->pending_disable_irq);
}
#define MAX_INTERRUPTS (~0ULL)
@ -5218,6 +5218,7 @@ static void perf_pending_task_sync(struct perf_event *event)
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);
@ -6749,7 +6750,7 @@ static void perf_sigtrap(struct perf_event *event)
/*
* Deliver the pending work in-event-context or follow the context.
*/
static void __perf_pending_irq(struct perf_event *event)
static void __perf_pending_disable(struct perf_event *event)
{
int cpu = READ_ONCE(event->oncpu);
@ -6787,11 +6788,26 @@ static void __perf_pending_irq(struct perf_event *event)
* irq_work_queue(); // FAILS
*
* irq_work_run()
* perf_pending_irq()
* perf_pending_disable()
*
* But the event runs on CPU-B and wants disabling there.
*/
irq_work_queue_on(&event->pending_irq, cpu);
irq_work_queue_on(&event->pending_disable_irq, cpu);
}
static void perf_pending_disable(struct irq_work *entry)
{
struct perf_event *event = container_of(entry, struct perf_event, pending_disable_irq);
int rctx;
/*
* If we 'fail' here, that's OK, it means recursion is already disabled
* and we won't recurse 'further'.
*/
rctx = perf_swevent_get_recursion_context();
__perf_pending_disable(event);
if (rctx >= 0)
perf_swevent_put_recursion_context(rctx);
}
static void perf_pending_irq(struct irq_work *entry)
@ -6814,8 +6830,6 @@ static void perf_pending_irq(struct irq_work *entry)
perf_event_wakeup(event);
}
__perf_pending_irq(event);
if (rctx >= 0)
perf_swevent_put_recursion_context(rctx);
}
@ -11956,6 +11970,7 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
init_waitqueue_head(&event->waitq);
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);