linux-kernel - Re: [patch 7/7] tidy up usermode helper waiting a bit

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Date:	Fri, 11 May 2007 13:01:38 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Johannes Berg <johannes@...solutions.net>
CC:	Andi Kleen <ak@...e.de>, Andrew Morton <akpm@...ux-foundation.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Chris Wright <chrisw@...s-sol.org>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Christoph Hellwig <hch@...radead.org>,
	Paul Mackerras <paulus@...ba.org>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Bjorn Helgaas <bjorn.helgaas@...com>,
	Joel Becker <joel.becker@...cle.com>,
	Tony Luck <tony.luck@...el.com>,
	Kay Sievers <kay.sievers@...y.org>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Oleg Nesterov <oleg@...sign.ru>,
	David Howells <dhowells@...hat.com>
Subject: Re: [patch 7/7] tidy up usermode helper waiting a bit

Johannes Berg wrote:
> [/me wonders why he was CC'ed]
>   

Because I knew you'd ask a good question ;)  No, I looked through the
recent changes on the files I changes and guessed at likely-looking
names.  But come to think of it, cc:ing completely random people is not
a bad way of getting some extra review cycles you mightn't otherwise get...


>>  	/* CLONE_VFORK: wait until the usermode helper has execve'd
>>  	 * successfully We need the data structures to stay around
>>  	 * until that is done.  */
>> -	if (wait)
>> +	if (wait == UMH_WAIT_PROC)
>>  		pid = kernel_thread(wait_for_helper, sub_info,
>>  				    CLONE_FS | CLONE_FILES | SIGCHLD);
>>  	else
>>  		pid = kernel_thread(____call_usermodehelper, sub_info,
>>  				    CLONE_VFORK | SIGCHLD);
>>     
>
> Isn't that a change in behaviour? Previously it said
> 	if (wait)
>  <=>	if (wait != 0)
>  <=>	if (wait != UMH_WAIT_EXEC)
> or am I missing something?
>   

Hm, you're right, it is a change in behaviour.  Yep, and a bug, since
its expecting wait_for_helper() to free the info in the UMH_NO_WAIT case.

---
 kernel/kmod.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

===================================================================
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -243,7 +243,7 @@ static void __call_usermodehelper(struct
 	/* CLONE_VFORK: wait until the usermode helper has execve'd
 	 * successfully We need the data structures to stay around
 	 * until that is done.  */
-	if (wait == UMH_WAIT_PROC)
+	if (wait == UMH_WAIT_PROC || wait == UMH_NO_WAIT)
 		pid = kernel_thread(wait_for_helper, sub_info,
 				    CLONE_FS | CLONE_FILES | SIGCHLD);
 	else

Thanks,
    J
-
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