On Wed, 31 Mar 2010 09:28:15 +0900 KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > On Tue, 30 Mar 2010 13:56:34 -0700 > Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > > That new BUG_ON() is triggering in Troels's machine when a bluetooth > > keyboard is enabled or disabled. See > > (https://bugzilla.kernel.org/show_bug.cgi?id=15648. > > > > I guess the question is: how did a kernel thread get a non-zero > > task->rss_stat.count[i]? If that's expected and OK then we will need > > to take some kernel-thread-avoidance action there. > > > It seems my fault that it's not initialized to be 0 at do_fork(), copy_process. > > About do_exit, do_exit() does this check. So, tsk->mm can be NULL. > > 949 if (group_dead) { > 950 hrtimer_cancel(&tsk->signal->real_timer); > 951 exit_itimers(tsk->signal); > 952 if (tsk->mm) > 953 setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm); > 954 } > > > Could whoever fixes this please also make __sync_task_rss_stat() > > static. > > > Ah, yes. I should do so. > > > I'll toss this over to Rafael/Maciej for tracking as a post-2.6.33 > > regression. > > > > Thanks. > > > > > == > > task->rss_stat wasn't initialized to 0 at copy_process(). > at exit, tsk->mm may be NULL. > And __sync_task_rss_stat() should be static. > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > --- > kernel/exit.c | 3 ++- > kernel/fork.c | 3 +++ > mm/memory.c | 2 +- > 3 files changed, 6 insertions(+), 2 deletions(-) > > 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); > 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 > @@ -124,7 +124,7 @@ 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; > > 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; OK, so the kenrel thread inherited a non-zero rss_stat from a userspace parent? With this fixed, the test for non-zero tsk->mm is't really needed in do_exit(), is it? I guess it makes sense though - sync_mm_rss() only really works for kernel threads by luck.. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>