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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <428beb0d-2484-4816-86c3-01e91bd7715a@kylinos.cn>
Date: Mon, 11 Aug 2025 17:42:34 +0800
From: Zihuan Zhang <zhangzihuan@...inos.cn>
To: Oleg Nesterov <oleg@...hat.com>
Cc: "Rafael J . Wysocki" <rafael@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>, David Hildenbrand <david@...hat.com>,
 Michal Hocko <mhocko@...e.com>, Jonathan Corbet <corbet@....net>,
 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>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 "Liam R . Howlett" <Liam.Howlett@...cle.com>,
 Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
 Suren Baghdasaryan <surenb@...gle.com>,
 Catalin Marinas <catalin.marinas@....com>, Nico Pache <npache@...hat.com>,
 xu xin <xu.xin16@....com.cn>, wangfushuai <wangfushuai@...du.com>,
 Andrii Nakryiko <andrii@...nel.org>, Christian Brauner <brauner@...nel.org>,
 Thomas Gleixner <tglx@...utronix.de>, Jeff Layton <jlayton@...nel.org>,
 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, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v1 5/9] freezer: set default freeze priority for
 PF_SUSPEND_TASK processes

在 2025/8/11 17:32, Oleg Nesterov 写道:
> On 08/11, Zihuan Zhang wrote:
>> 在 2025/8/8 22:39, Oleg Nesterov 写道:
>>> On 08/07, Zihuan Zhang wrote:
>>>> --- 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);
>>> But why?
>>>
>>> Again, freeze_task() will return false anyway, this process is
>>> PF_SUSPEND_TASK.
>> I  think there is resaon put it here. For example, systemd-sleep is a
>> user-space process that executes the suspend flow.
>>
>>   If we don’t set its freeze priority explicitly, our current code may end up
>> with this user process being the last one that cannot freeze.
> How so? sorry I don't follow.

The problem is in this part:

+            if (user_only && !(p->flags & PF_KTHREAD) && round < 
p->freeze_priority)
+                continue;

PF_SUSPEND_TASK is a user process, so it meets the “needs freezing” 
condition and todo gets incremented. But it actually doesn’t need to 
freeze, so resulting in an infinite loop

> Oleg.
>