Re: 3.4-rc7: BUG: Bad rss-counter state mm:ffff88040b56f800 idx:1val:-59

[Martin Mokrejs]

Hi,
  I rebooted the laptop twice today after just brief uses and the messages did not
appear in the logs.

Now I just applied the below patch and during two reboots it did not appear either.
Do I have to use the computer for some longer while to reproduce the issue? ;-)

I will stay with the patch applied over 3.4-rc7 and would the BUG: re-appear I will
let you know. But I doubt at the moment I could confirm it really helped.
Clues how to reproduce? ;)
Martin

Andrew Morton wrote:
> On Wed, 23 May 2012 00:41:28 +0200
> Martin Mokrejs <mmokrejs@xxxxxxxxxxxxxxxxxx> wrote:
> 
>> Hi Andrew,
>>   while shutting down my laptop (Dell Vostro 3550 with 16GB RAM, core i7) with 3.4-rc7 I got:
>>
>> May 23 00:07:54 vostro kernel: [352687.968267] BUG: Bad rss-counter state mm:ffff88040b56f800 idx:1 val:-59
>> May 23 00:07:54 vostro kernel: [352687.968312] BUG: Bad rss-counter state mm:ffff88040b56f800 idx:2 val:59
>> May 23 00:07:55 vostro acpid: exiting
>> May 23 00:07:55 vostro syslog-ng[2838]: syslog-ng shutting down; version='3.3.4'
>>
>>   I found by Google the below thread and thought that maybe it is related?
>> http://comments.gmane.org/gmane.linux.kernel.mm/76459
>>
>> ...
>>
> 
> 
> Well hopefully the below will fix this?
> 
> I notice that I don't have this tagged for -stable backporting.  That
> seems wrong.  Konstantin, do we know for how long this bug has been in
> there?
> 
> 
> 
> From: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx>
> Subject: mm: correctly synchronize rss-counters at exit/exec
> 
> mm->rss_stat counters have per-task delta: task->rss_stat.  Before
> changing task->mm pointer the kernel must flush this delta with
> sync_mm_rss().
> 
> do_exit() already calls sync_mm_rss() to flush the rss-counters before
> committing the rss statistics into task->signal->maxrss, taskstats, audit
> and other stuff.  Unfortunately the kernel does this before calling
> mm_release(), which can call put_user() for processing
> task->clear_child_tid.  So at this point we can trigger page-faults and
> task->rss_stat becomes non-zero again.  As a result mm->rss_stat becomes
> inconsistent and check_mm() will print something like this:
> 
> | BUG: Bad rss-counter state mm:ffff88020813c380 idx:1 val:-1
> | BUG: Bad rss-counter state mm:ffff88020813c380 idx:2 val:1
> 
> This patch moves sync_mm_rss() into mm_release(), and moves mm_release()
> out of do_exit() and calls it earlier.  After mm_release() there should be
> no pagefaults.
> 
> [akpm@xxxxxxxxxxxxxxxxxxxx: tweak comment]
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx>
> Reported-by: Markus Trippelsdorf <markus@xxxxxxxxxxxxxxx>
> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---
> 
>  fs/exec.c     |    1 -
>  kernel/exit.c |   13 ++++++++-----
>  kernel/fork.c |    8 ++++++++
>  3 files changed, 16 insertions(+), 6 deletions(-)
> 
> diff -puN fs/exec.c~mm-correctly-synchronize-rss-counters-at-exit-exec fs/exec.c
> --- a/fs/exec.c~mm-correctly-synchronize-rss-counters-at-exit-exec
> +++ a/fs/exec.c
> @@ -823,7 +823,6 @@ static int exec_mmap(struct mm_struct *m
>  	/* Notify parent that we're no longer interested in the old VM */
>  	tsk = current;
>  	old_mm = current->mm;
> -	sync_mm_rss(old_mm);
>  	mm_release(tsk, old_mm);
>  
>  	if (old_mm) {
> diff -puN kernel/exit.c~mm-correctly-synchronize-rss-counters-at-exit-exec kernel/exit.c
> --- a/kernel/exit.c~mm-correctly-synchronize-rss-counters-at-exit-exec
> +++ a/kernel/exit.c
> @@ -423,6 +423,7 @@ void daemonize(const char *name, ...)
>  	 * user space pages.  We don't need them, and if we didn't close them
>  	 * they would be locked into memory.
>  	 */
> +	mm_release(current, current->mm);
>  	exit_mm(current);
>  	/*
>  	 * We don't want to get frozen, in case system-wide hibernation
> @@ -640,7 +641,6 @@ static void exit_mm(struct task_struct *
>  	struct mm_struct *mm = tsk->mm;
>  	struct core_state *core_state;
>  
> -	mm_release(tsk, mm);
>  	if (!mm)
>  		return;
>  	/*
> @@ -959,9 +959,13 @@ void do_exit(long code)
>  				preempt_count());
>  
>  	acct_update_integrals(tsk);
> -	/* sync mm's RSS info before statistics gathering */
> -	if (tsk->mm)
> -		sync_mm_rss(tsk->mm);
> +
> +	/* Set exit_code before complete_vfork_done() in mm_release() */
> +	tsk->exit_code = code;
> +
> +	/* Release mm and sync mm's RSS info before statistics gathering */
> +	mm_release(tsk, tsk->mm);
> +
>  	group_dead = atomic_dec_and_test(&tsk->signal->live);
>  	if (group_dead) {
>  		hrtimer_cancel(&tsk->signal->real_timer);
> @@ -974,7 +978,6 @@ void do_exit(long code)
>  		tty_audit_exit();
>  	audit_free(tsk);
>  
> -	tsk->exit_code = code;
>  	taskstats_exit(tsk, group_dead);
>  
>  	exit_mm(tsk);
> diff -puN kernel/fork.c~mm-correctly-synchronize-rss-counters-at-exit-exec kernel/fork.c
> --- a/kernel/fork.c~mm-correctly-synchronize-rss-counters-at-exit-exec
> +++ a/kernel/fork.c
> @@ -809,6 +809,14 @@ void mm_release(struct task_struct *tsk,
>  		}
>  		tsk->clear_child_tid = NULL;
>  	}
> +
> +	/*
> +	 * Final rss-counter synchronization. After this point there must be
> +	 * no pagefaults into this mm from the current context.  Otherwise
> +	 * mm->rss_stat will be inconsistent.
> +	 */
> +	if (mm)
> +		sync_mm_rss(mm);
>  }
>  
>  /*
> _
> 
> .
> 
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