linux-kernel - Re: [PATCH v2 1/4] PM: freezer: Add retry count statistics for freeze pass iterations

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: <146a072b-53fd-474c-923a-9f5574c55aac@kylinos.cn>
Date: Fri, 4 Jul 2025 08:32:26 +0800
From: Zihuan Zhang <zhangzihuan@...inos.cn>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: pavel@...nel.org, len.brown@...el.com, linux-pm@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/4] PM: freezer: Add retry count statistics for freeze
 pass iterations

Hi Rafael,
Thanks for the feedback.

在 2025/7/3 22:38, Rafael J. Wysocki 写道:
> On Thu, Jun 19, 2025 at 5:54 AM Zihuan Zhang <zhangzihuan@...inos.cn> wrote:
>> Freezer retry loops during suspend are often triggered by tasks entering
>> D-state (TASK_UNINTERRUPTIBLE), which cannot be frozen.  This patch adds
>> a simple retry counter to freeze_processes() to help quantify how many
>> attempts were required before all tasks entered the frozen state. This
>> is useful for performance tuning and debugging unpredictable suspend
>> delays.
>>
>> A new dmesg log is added for visibility:
>>
>> freeze round: xx, tasks to freeze: xx
>>
>> This message allows users to correlate freeze instability with system
>> state.
>>
>> Signed-off-by: Zihuan Zhang <zhangzihuan@...inos.cn>
>> ---
>>   kernel/power/process.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/kernel/power/process.c b/kernel/power/process.c
>> index dc0dfc349f22..87616ca710ac 100644
>> --- a/kernel/power/process.c
>> +++ b/kernel/power/process.c
>> @@ -32,6 +32,7 @@ static int try_to_freeze_tasks(bool user_only)
>>          struct task_struct *g, *p;
>>          unsigned long end_time;
>>          unsigned int todo;
>> +       unsigned int retry = 0;
>>          bool wq_busy = false;
>>          ktime_t start, end, elapsed;
>>          unsigned int elapsed_msecs;
>> @@ -63,6 +64,8 @@ static int try_to_freeze_tasks(bool user_only)
>>                          todo += wq_busy;
>>                  }
>>
>> +               pm_pr_dbg("freeze round: %d, task to freeze: %d\n", retry, todo);
>> +
> This is kind of fine if it is really needed, but it needs to have a
> separate on/off switch as far as I'm concerned.
>
> Maybe use pr_debug() for it in which case it would be controlled via
> dynamic debug?
I agree with your suggestion — I’ll switch to pr_debug() in the next 
version so that the message can be controlled via dynamic debug.
>>                  if (!todo || time_after(jiffies, end_time))
>>                          break;
>>
>> @@ -79,6 +82,7 @@ static int try_to_freeze_tasks(bool user_only)
>>                  usleep_range(sleep_usecs / 2, sleep_usecs);
>>                  if (sleep_usecs < 8 * USEC_PER_MSEC)
>>                          sleep_usecs *= 2;
>> +               retry++;
>>          }
>>
>>          end = ktime_get_boottime();
>> --
>> 2.25.1
>>
Best regards,
Zihuan Zhang