linux-kernel - [RFC PATCH v1 5/9] freezer: set default freeze priority for PF_SUSPEND

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Message-Id: <20250807121418.139765-6-zhangzihuan@kylinos.cn>
Date: Thu,  7 Aug 2025 20:14:14 +0800
From: Zihuan Zhang <zhangzihuan@...inos.cn>
To: "Rafael J . Wysocki" <rafael@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Oleg Nesterov <oleg@...hat.com>,
	David Hildenbrand <david@...hat.com>,
	Michal Hocko <mhocko@...e.com>,
	Jonathan Corbet <corbet@....net>
Cc: Ingo Molnar <mingo@...hat.com>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>,
	Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>,
	len brown <len.brown@...el.com>,
	pavel machek <pavel@...nel.org>,
	Kees Cook <kees@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
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	"Liam R . Howlett" <Liam.Howlett@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
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	Andrii Nakryiko <andrii@...nel.org>,
	Christian Brauner <brauner@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
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	Al Viro <viro@...iv.linux.org.uk>,
	Adrian Ratiu <adrian.ratiu@...labora.com>,
	linux-pm@...r.kernel.org,
	linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org,
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	linux-kernel@...r.kernel.org,
	Zihuan Zhang <zhangzihuan@...inos.cn>
Subject: [RFC PATCH v1 5/9] freezer: set default freeze priority for PF_SUSPEND_TASK processes

Tasks marked with PF_SUSPEND_TASK are involved in system suspend or
hibernate operations. These tasks must not be frozen, as they are
responsible for coordinating or executing parts of the suspend/resume
sequence.

This patch explicitly sets their freeze_priority to FREEZE_PRIORITY_NEVER
during initialization. This makes their exemption from the freezer logic
clear in the new freeze-priority model and avoids redundant evaluations
during process traversal.

Signed-off-by: Zihuan Zhang <zhangzihuan@...inos.cn>
---
 kernel/power/process.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/power/process.c b/kernel/power/process.c
index 06eafdb32abb..21bbca7040cf 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -147,6 +147,7 @@ int freeze_processes(void)
 
 	pm_wakeup_clear(0);
 	pm_freezing = true;
+	freeze_set_default_priority(current, FREEZE_PRIORITY_NEVER);
 	error = try_to_freeze_tasks(true);
 	if (!error)
 		__usermodehelper_set_disable_depth(UMH_DISABLED);
@@ -218,6 +219,7 @@ void thaw_processes(void)
 	WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
 	curr->flags &= ~PF_SUSPEND_TASK;
 
+	freeze_set_default_priority(current, FREEZE_PRIORITY_NORMAL);
 	usermodehelper_enable();
 
 	schedule();
-- 
2.25.1