linux-kernel - [RFC PATCH] PM: dpm: add module param to backtrace all CPUs

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Message-ID: <20250723035955.486688-1-senozhatsky@chromium.org>
Date: Wed, 23 Jul 2025 12:59:09 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>,
	Pavel Machek <pavel@...nel.org>
Cc: Tomasz Figa <tfiga@...omium.org>,
	linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: [RFC PATCH] PM: dpm: add module param to backtrace all CPUs

Add dpm_all_cpu_backtrace module parameter which controls
all CPU backtrace dump before DPM panics the system.  This
is expected to help understanding what might have caused
device timeout.

Signed-off-by: Sergey Senozhatsky <senozhatsky@...omium.org>
---
 drivers/base/power/main.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index dbf5456cd891..9fb943afe246 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -34,6 +34,7 @@
 #include <linux/cpufreq.h>
 #include <linux/devfreq.h>
 #include <linux/timer.h>
+#include <linux/nmi.h>
 
 #include "../base.h"
 #include "power.h"
@@ -517,6 +518,9 @@ struct dpm_watchdog {
 #define DECLARE_DPM_WATCHDOG_ON_STACK(wd) \
 	struct dpm_watchdog wd
 
+static bool __read_mostly dpm_all_cpu_backtrace;
+module_param(dpm_all_cpu_backtrace, bool, 0644);
+
 /**
  * dpm_watchdog_handler - Driver suspend / resume watchdog handler.
  * @t: The timer that PM watchdog depends on.
@@ -532,8 +536,12 @@ static void dpm_watchdog_handler(struct timer_list *t)
 	unsigned int time_left;
 
 	if (wd->fatal) {
+		unsigned int this_cpu = smp_processor_id();
+
 		dev_emerg(wd->dev, "**** DPM device timeout ****\n");
 		show_stack(wd->tsk, NULL, KERN_EMERG);
+		if (dpm_all_cpu_backtrace)
+			trigger_single_cpu_backtrace(this_cpu);
 		panic("%s %s: unrecoverable failure\n",
 			dev_driver_string(wd->dev), dev_name(wd->dev));
 	}
-- 
2.50.0.727.gbf7dc18ff4-goog