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

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Date:	Wed, 23 May 2012 19:21:46 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Martin Mokrejs <mmokrejs@...d.natur.cuni.cz>,
	LKML <linux-kernel@...r.kernel.org>, khlebnikov@...nvz.org,
	markus@...ppelsdorf.de, hughd@...gle.com,
	kamezawa.hiroyu@...fujitsu.com, Michal Hocko <mhocko@...e.cz>,
	linux-mm@...ck.org
Subject: Re: 3.4-rc7: BUG: Bad rss-counter state mm:ffff88040b56f800 idx:1
	val:-59

On 05/22, Andrew Morton wrote:
>
> Also, I have a note here that Oleg was unhappy with the patch.  Oleg
> happiness is important.  Has he cheered up yet?

Well, yes, I do not really like this patch ;) Because I think there is
a more simple/straightforward fix, see below. In my opinion it also
makes the original code simpler.

But. Obviously this is subjective, I can't prove my patch is "better",
and I didn't try to test it.

So I won't argue with Konstantin who dislikes my patch, although I
would like to know the reason.

Oleg.


--- a/kernel/tsacct.c
+++ b/kernel/tsacct.c
@@ -91,6 +91,7 @@ void xacct_add_tsk(struct taskstats *sta
 	stats->virtmem = p->acct_vm_mem1 * PAGE_SIZE / MB;
 	mm = get_task_mm(p);
 	if (mm) {
+		sync_mm_rss(mm);
 		/* adjust to KB unit */
 		stats->hiwater_rss   = get_mm_hiwater_rss(mm) * PAGE_SIZE / KB;
 		stats->hiwater_vm    = get_mm_hiwater_vm(mm)  * PAGE_SIZE / KB;
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -643,6 +643,8 @@ static void exit_mm(struct task_struct *
 	mm_release(tsk, mm);
 	if (!mm)
 		return;
+
+	sync_mm_rss(mm);
 	/*
 	 * Serialize with any possible pending coredump.
 	 * We must hold mmap_sem around checking core_state
@@ -960,9 +962,6 @@ 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);
 	group_dead = atomic_dec_and_test(&tsk->signal->live);
 	if (group_dead) {
 		hrtimer_cancel(&tsk->signal->real_timer);
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -823,10 +823,10 @@ 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) {
+		sync_mm_rss(old_mm);
 		/*
 		 * Make sure that if there is a core dump in progress
 		 * for the old mm, we get out and die instead of going


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