On Wed, 23 May 2012 00:41:28 +0200 Martin Mokrejs <mmokrejs@xxxxxxxxxxxxxxxxxx> wrote: > Hi Andrew, > while shutting down my laptop (Dell Vostro 3550 with 16GB RAM, core i7) with 3.4-rc7 I got: > > May 23 00:07:54 vostro kernel: [352687.968267] BUG: Bad rss-counter state mm:ffff88040b56f800 idx:1 val:-59 > May 23 00:07:54 vostro kernel: [352687.968312] BUG: Bad rss-counter state mm:ffff88040b56f800 idx:2 val:59 > May 23 00:07:55 vostro acpid: exiting > May 23 00:07:55 vostro syslog-ng[2838]: syslog-ng shutting down; version='3.3.4' > > I found by Google the below thread and thought that maybe it is related? > http://comments.gmane.org/gmane.linux.kernel.mm/76459 > > ... > Well hopefully the below will fix this? I notice that I don't have this tagged for -stable backporting. That seems wrong. Konstantin, do we know for how long this bug has been in there? From: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx> Subject: mm: correctly synchronize rss-counters at exit/exec mm->rss_stat counters have per-task delta: task->rss_stat. Before changing task->mm pointer the kernel must flush this delta with sync_mm_rss(). do_exit() already calls sync_mm_rss() to flush the rss-counters before committing the rss statistics into task->signal->maxrss, taskstats, audit and other stuff. Unfortunately the kernel does this before calling mm_release(), which can call put_user() for processing task->clear_child_tid. So at this point we can trigger page-faults and task->rss_stat becomes non-zero again. As a result mm->rss_stat becomes inconsistent and check_mm() will print something like this: | BUG: Bad rss-counter state mm:ffff88020813c380 idx:1 val:-1 | BUG: Bad rss-counter state mm:ffff88020813c380 idx:2 val:1 This patch moves sync_mm_rss() into mm_release(), and moves mm_release() out of do_exit() and calls it earlier. After mm_release() there should be no pagefaults. [akpm@xxxxxxxxxxxxxxxxxxxx: tweak comment] Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx> Reported-by: Markus Trippelsdorf <markus@xxxxxxxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/exec.c | 1 - kernel/exit.c | 13 ++++++++----- kernel/fork.c | 8 ++++++++ 3 files changed, 16 insertions(+), 6 deletions(-) diff -puN fs/exec.c~mm-correctly-synchronize-rss-counters-at-exit-exec fs/exec.c --- a/fs/exec.c~mm-correctly-synchronize-rss-counters-at-exit-exec +++ a/fs/exec.c @@ -823,7 +823,6 @@ 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) { diff -puN kernel/exit.c~mm-correctly-synchronize-rss-counters-at-exit-exec kernel/exit.c --- a/kernel/exit.c~mm-correctly-synchronize-rss-counters-at-exit-exec +++ a/kernel/exit.c @@ -423,6 +423,7 @@ void daemonize(const char *name, ...) * user space pages. We don't need them, and if we didn't close them * they would be locked into memory. */ + mm_release(current, current->mm); exit_mm(current); /* * We don't want to get frozen, in case system-wide hibernation @@ -640,7 +641,6 @@ static void exit_mm(struct task_struct * struct mm_struct *mm = tsk->mm; struct core_state *core_state; - mm_release(tsk, mm); if (!mm) return; /* @@ -959,9 +959,13 @@ 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); + + /* Set exit_code before complete_vfork_done() in mm_release() */ + tsk->exit_code = code; + + /* Release mm and sync mm's RSS info before statistics gathering */ + mm_release(tsk, tsk->mm); + group_dead = atomic_dec_and_test(&tsk->signal->live); if (group_dead) { hrtimer_cancel(&tsk->signal->real_timer); @@ -974,7 +978,6 @@ void do_exit(long code) tty_audit_exit(); audit_free(tsk); - tsk->exit_code = code; taskstats_exit(tsk, group_dead); exit_mm(tsk); diff -puN kernel/fork.c~mm-correctly-synchronize-rss-counters-at-exit-exec kernel/fork.c --- a/kernel/fork.c~mm-correctly-synchronize-rss-counters-at-exit-exec +++ a/kernel/fork.c @@ -809,6 +809,14 @@ void mm_release(struct task_struct *tsk, } tsk->clear_child_tid = NULL; } + + /* + * Final rss-counter synchronization. After this point there must be + * no pagefaults into this mm from the current context. Otherwise + * mm->rss_stat will be inconsistent. + */ + if (mm) + sync_mm_rss(mm); } /* _ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>