perf: Move irq_work_queue() where the event is prepared.

Only if perf_event::pending_sigtrap is zero, the irq_work accounted by
increminging perf_event::nr_pending. The member perf_event::pending_addr
might be overwritten by a subsequent event if the signal was not yet
delivered and is expected. The irq_work will not be enqeueued again
because it has a check to be only enqueued once.

Move irq_work_queue() to where the counter is incremented and
perf_event::pending_sigtrap is set to make it more obvious that the
irq_work is scheduled once.

Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Tested-by: Marco Elver <[email protected]>
Tested-by: Arnaldo Carvalho de Melo <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: Sebastian Andrzej Siewior

kernel/events/core.c

@@ -9727,6 +9727,11 @@ static int __perf_event_overflow(struct perf_event *event,
 		if (!event->pending_sigtrap) {
 			event->pending_sigtrap = pending_id;
 			local_inc(&event->ctx->nr_pending);
+
+			event->pending_addr = 0;
+			if (valid_sample && (data->sample_flags & PERF_SAMPLE_ADDR))
+				event->pending_addr = data->addr;
+			irq_work_queue(&event->pending_irq);
 		} else if (event->attr.exclude_kernel && valid_sample) {
 			/*
 			 * Should not be able to return to user space without
@@ -9742,11 +9747,6 @@ static int __perf_event_overflow(struct perf_event *event,
 			 */
 			WARN_ON_ONCE(event->pending_sigtrap != pending_id);
 		}
-
-		event->pending_addr = 0;
-		if (valid_sample && (data->sample_flags & PERF_SAMPLE_ADDR))
-			event->pending_addr = data->addr;
-		irq_work_queue(&event->pending_irq);
 	}
 
 	READ_ONCE(event->overflow_handler)(event, data, regs);