linux-kernel - Re: [PATCH] perf: Fix missing SIGTRAPs

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Date:   Fri, 7 Oct 2022 15:09:16 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Marco Elver <elver@...gle.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH] perf: Fix missing SIGTRAPs

On Fri, Oct 07, 2022 at 11:37:34AM +0200, Marco Elver wrote:

> That worked. In addition I had to disable the ctx->task != current check
> if we're in task_work, because presumably the event might have already
> been disabled/moved??

Uhmmm... uhhh... damn. (wall-time was significantly longer)

Does this help?

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6490,8 +6490,8 @@ static void __perf_pending_irq(struct pe
 	if (cpu == smp_processor_id()) {
 		if (event->pending_sigtrap) {
 			event->pending_sigtrap = 0;
-			local_dec(&event->ctx->nr_pending);
 			perf_sigtrap(event);
+			local_dec(&event->ctx->nr_pending);
 		}
 		if (event->pending_disable) {
 			event->pending_disable = 0;
@@ -6563,8 +6563,8 @@ static void perf_pending_task(struct cal
 
 	if (event->pending_work) {
 		event->pending_work = 0;
-		local_dec(&event->ctx->nr_pending);
 		perf_sigtrap(event);
+		local_dec(&event->ctx->nr_pending);
 	}
 
 	if (rctx >= 0)