linux-kernel - Re: [PATCH RFC 09/13] exit: Use for_each_thread() in do

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Date:	Wed, 27 May 2015 12:33:49 +0300
From:	Kirill Tkhai <tkhai@...dex.ru>
To:	Oleg Nesterov <oleg@...hat.com>, Kirill Tkhai <ktkhai@...n.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Michal Hocko <mhocko@...e.cz>, Rik van Riel <riel@...hat.com>,
	Ionut Alexa <ionut.m.alexa@...il.com>,
	Peter Hurley <peter@...leysoftware.com>
Subject: Re: [PATCH RFC 09/13] exit: Use for_each_thread() in do_wait()

26.05.2015, 22:47, "Oleg Nesterov" <oleg@...hat.com>:
> On 05/25, Kirill Tkhai wrote:
>>  Refactoring, no functionality change.
>
> Hmm. unless I missed something this change is wrong.
>
>>  --- a/kernel/exit.c
>>  +++ b/kernel/exit.c
>>  @@ -1538,8 +1538,7 @@ static long do_wait(struct wait_opts *wo)
>>
>>           set_current_state(TASK_INTERRUPTIBLE);
>>           read_lock(&tasklist_lock);
>>  - tsk = current;
>>  - do {
>>  + for_each_thread(current, tsk) {
>>                   retval = do_wait_thread(wo, tsk);
>>                   if (retval)
>>                           goto end;
>>  @@ -1550,7 +1549,7 @@ static long do_wait(struct wait_opts *wo)
>>
>>                   if (wo->wo_flags & __WNOTHREAD)
>>                           break;
>>  - } while_each_thread(current, tsk);
>>  + }
>
> Please note the __WNOTHREAD check. This is the rare case when we
> actually want while_each_thread() (although it should die anyway).
>
> for_each_thread() always starts from ->group_leader, but we need
> to start from "current" first.

Sure, this must be like below. Thanks!
I won't resend the whole series with only this one patch changed to
do not bomb mail boxes. Waiting for the review.

diff --git a/kernel/exit.c b/kernel/exit.c
index a268093..e4963d3 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1538,8 +1538,10 @@ static long do_wait(struct wait_opts *wo)
 
 	set_current_state(TASK_INTERRUPTIBLE);
 	read_lock(&tasklist_lock);
-	tsk = current;
-	do {
+	for_each_thread(current, tsk) {
+		if (wo->wo_flags & __WNOTHREAD)
+			tsk = current;
+
 		retval = do_wait_thread(wo, tsk);
 		if (retval)
 			goto end;
@@ -1550,7 +1552,7 @@ static long do_wait(struct wait_opts *wo)
 
 		if (wo->wo_flags & __WNOTHREAD)
 			break;
-	} while_each_thread(current, tsk);
+	}
 	read_unlock(&tasklist_lock);
 
 notask:
--
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