On Tue, 30 Mar 2010 20:03:36 -0400
Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Wed, 31 Mar 2010 11:53:00 +0900 Minchan Kim <minchan.kim@xxxxxxxxx> wrote:
> really. Apart from the fact that we'll otherwise perform an empty
> NR_MM_COUNTERS loop in __sync_task_rss_stat(), sync_mm_rss() just isn't
> set up to handle kernel threads. Given that the function of
> sync_task_mm(from, to) is to move stuff from "from" and into "to", it's
> daft to call it with a NULL value of `to'!
>
Updated again.
==
task->rss_stat wasn't initialized to 0 at copy_process().
At exit, tsk->mm may be NULL. It's not valid to call sync_mm_rss()
against not exisiting mm_struct, We should check it.
And __sync_task_rss_stat() should be static.
This patch also removes BUG_ON(!mm) in __sync_task_rss_stat().
The code will panic if !mm without it.
Changelog:
- removed BUG_ON()
- added check task->mm in exit.c before calling sync_mm_rss().
Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxxx>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
kernel/exit.c | 3 ++-
kernel/fork.c | 3 +++
mm/memory.c | 3 +--
3 files changed, 6 insertions(+), 3 deletions(-)
Index: mmotm-2.6.34-Mar24/mm/memory.c
===================================================================
--- mmotm-2.6.34-Mar24.orig/mm/memory.c
+++ mmotm-2.6.34-Mar24/mm/memory.c
@@ -124,13 +124,12 @@ core_initcall(init_zero_pfn);
#if defined(SPLIT_RSS_COUNTING)
-void __sync_task_rss_stat(struct task_struct *task, struct mm_struct *mm)
+static void __sync_task_rss_stat(struct task_struct *task, struct mm_struct *mm)
{
int i;
for (i = 0; i < NR_MM_COUNTERS; i++) {
if (task->rss_stat.count[i]) {
- BUG_ON(!mm);
add_mm_counter(mm, i, task->rss_stat.count[i]);
task->rss_stat.count[i] = 0;
}
Index: mmotm-2.6.34-Mar24/kernel/fork.c
===================================================================
--- mmotm-2.6.34-Mar24.orig/kernel/fork.c
+++ mmotm-2.6.34-Mar24/kernel/fork.c
@@ -1060,6 +1060,9 @@ static struct task_struct *copy_process(
p->prev_utime = cputime_zero;
p->prev_stime = cputime_zero;
#endif
+#if defined(SPLIT_RSS_COUNTING)
+ memset(&p->rss_stat, 0, sizeof(p->rss_stat));
+#endif
p->default_timer_slack_ns = current->timer_slack_ns;
Index: mmotm-2.6.34-Mar24/kernel/exit.c
===================================================================
--- mmotm-2.6.34-Mar24.orig/kernel/exit.c
+++ mmotm-2.6.34-Mar24/kernel/exit.c
@@ -950,7 +950,8 @@ NORET_TYPE void do_exit(long code)
acct_update_integrals(tsk);
/* sync mm's RSS info before statistics gathering */
- sync_mm_rss(tsk, tsk->mm);
+ if (tsk->mm)
+ sync_mm_rss(tsk, tsk->mm);
group_dead = atomic_dec_and_test(&tsk->signal->live);
if (group_dead) {
hrtimer_cancel(&tsk->signal->real_timer);
--
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