linux-kernel - Re: PATCH: freezer: add fake signal clearing back when thaw task

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Message-ID: <20130226142804.GC28940@redhat.com>
Date:	Tue, 26 Feb 2013 15:28:04 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Lianwei Wang <lianwei.wang@...il.com>,
	linux-kernel@...r.kernel.org, "Rafael J. Wysocki" <rjw@...k.pl>,
	Mandeep Singh Baines <msb@...omium.org>
Subject: Re: PATCH: freezer: add fake signal clearing back when thaw task

Ah, I just noticed that the changelog mentions wait_event_freezable() too,

On 02/25, Tejun Heo wrote:
>
> > Subject: [PATCH] freezer: add fake signal clearing back when thaw task
> >
> > The fake TIF_SIGPENDING is set during freeze userspace process, but it
> > is not cleared when thaw tasks after below commit:
> >   34b087e freezer: kill unused set_freezable_with_signal()
> >
> > This will cause the userspace task that wait_event_freezable

But there is no userspace users?

I guess wait_event_freezable() is only used to avoid the contribution
to load_avg. So we can simplify it, __wait_event_freezable() can simply
do freezable_schedule() or wait_event_freezable() can do
freezer_do_not_count + wait_event_interruptible. Or we are going to add
more users?

As for current users, I think they do not need this interface. Something
like below. I was going to try to convert khugepaged/ksm_scan_thread
yesterday but I was distracted, will try to do tomorrow.

Oleg.

--- x/mm/huge_memory.c
+++ x/mm/huge_memory.c
@@ -2616,7 +2616,7 @@ static int khugepaged_has_work(void)
 static int khugepaged_wait_event(void)
 {
 	return !list_empty(&khugepaged_scan.mm_head) ||
-		kthread_should_stop();
+		kthread_should_stop_or_freeze();
 }
 
 static void khugepaged_do_scan(void)
@@ -2655,20 +2655,18 @@ static void khugepaged_do_scan(void)
 
 static void khugepaged_wait_work(void)
 {
-	try_to_freeze();
-
 	if (khugepaged_has_work()) {
 		if (!khugepaged_scan_sleep_millisecs)
 			return;
 
-		wait_event_freezable_timeout(khugepaged_wait,
-					     kthread_should_stop(),
+		wait_event_interruptible_timeout(khugepaged_wait,
+					     kthread_should_stop_or_freeze(),
 			msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
 		return;
 	}
 
 	if (khugepaged_enabled())
-		wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
+		wait_event_interruptible(khugepaged_wait, khugepaged_wait_event());
 }
 
 static int khugepaged(void *none)
@@ -2678,7 +2676,7 @@ static int khugepaged(void *none)
 	set_freezable();
 	set_user_nice(current, 19);
 
-	while (!kthread_should_stop()) {
+	while (!kthread_freezable_should_stop(NULL)) {
 		khugepaged_do_scan();
 		khugepaged_wait_work();
 	}

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