linux-ext4 - Re: [PATCH] Check for error returned by kthread

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Message-ID: <462359B2.7070706@sw.ru>
Date:	Mon, 16 Apr 2007 15:10:42 +0400
From:	Pavel Emelianov <xemul@...ru>
To:	Christoph Hellwig <hch@...radead.org>
CC:	sct@...hat.com, akpm@...ux-foundation.org,
	linux-ext4@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	devel@...nvz.org
Subject: Re: [PATCH] Check for error returned by kthread_create on creating
 journal thread

Christoph Hellwig wrote:
> On Mon, Apr 16, 2007 at 11:41:14AM +0400, Pavel Emelianov wrote:
>> If the thread failed to create the subsequent wait_event
>> will hang forever.
>>
>> This is likely to happen if kernel hits max_threads limit.
>>
>> Will be critical for virtualization systems that limit the
>> number of tasks and kernel memory usage within the container.
> 
>> --- ./fs/jbd/journal.c.jbdthreads	2007-04-16 11:17:36.000000000 +0400
>> +++ ./fs/jbd/journal.c	2007-04-16 11:30:09.000000000 +0400
>> @@ -211,10 +211,16 @@ end_loop:
>>  	return 0;
>>  }
>>  
>> -static void journal_start_thread(journal_t *journal)
>> +static int journal_start_thread(journal_t *journal)
>>  {
>> -	kthread_run(kjournald, journal, "kjournald");
>> +	struct task_struct *t;
>> +
>> +	t = kthread_run(kjournald, journal, "kjournald");
>> +	if (IS_ERR(t))
>> +		return PTR_ERR(t);
>> +
>>  	wait_event(journal->j_wait_done_commit, journal->j_task != 0);
> 
> Note that this wait_event should exist at all, and the return

Should NOT you mean?

> value of kthread_run should be assigned to journal->j_task.  Also
> the code doesn't use the kthread primitives in other places leading
> to crufty code.

Well, this could be done with a separate patch, I think.

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