linux-kernel - [PATCH v3 1/4] perf: Move irq_work_queue() where the event is prepared.

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Date: Fri, 22 Mar 2024 07:48:21 +0100
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Adrian Hunter <adrian.hunter@...el.com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Ingo Molnar <mingo@...hat.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Marco Elver <elver@...gle.com>,
	Mark Rutland <mark.rutland@....com>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH v3 1/4] 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.

Tested-by: Marco Elver <elver@...gle.com>
Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 kernel/events/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index f0f0f71213a1d..c7a0274c662c8 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -9595,6 +9595,7 @@ static int __perf_event_overflow(struct perf_event *event,
 		if (!event->pending_sigtrap) {
 			event->pending_sigtrap = pending_id;
 			local_inc(&event->ctx->nr_pending);
+			irq_work_queue(&event->pending_irq);
 		} else if (event->attr.exclude_kernel && valid_sample) {
 			/*
 			 * Should not be able to return to user space without
@@ -9614,7 +9615,6 @@ static int __perf_event_overflow(struct perf_event *event,
 		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);
-- 
2.43.0