Messages in this thread Patch in this message | | | Date | Wed, 31 Mar 2010 12:11:20 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH] exit: fix oops in sync_mm_rss |
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On Tue, 30 Mar 2010 20:03:36 -0400 Andrew Morton <akpm@linux-foundation.org> wrote:
> On Wed, 31 Mar 2010 11:53:00 +0900 Minchan Kim <minchan.kim@gmail.com> 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@gmail.com> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> --- 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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