On Tue, 30 Mar 2010 17:37:21 -0400 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > 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? > I think so. > 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.. At first, I considered so, too. But I changed my mind to show "we know tsk->mm can be NULL here!" by code. Because __sync_mm_rss_stat() has BUG_ON(!mm), the code reader will think tsk->mm shouldn't be NULL always. Doesn't make sense ? Thanks, -Kame -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
