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authorKonstantin Khlebnikov <khlebnikov@openvz.org>2012-06-07 14:21:14 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-06-07 14:43:55 -0700
commit40af1bbdca47e5c8a2044039bb78ca8fd8b20f94 (patch)
tree70b5a21579f8b0137c09e54d523246d84be93430 /kernel/exit.c
parent39caa0916ef27cf1da5026eb708a2b8413156f75 (diff)
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@linux-foundation.org: tweak comment] Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org> Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de> Cc: Hugh Dickins <hughd@google.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: <stable@vger.kernel.org> [3.4.x] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/exit.c')
-rw-r--r--kernel/exit.c13
1 files changed, 8 insertions, 5 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index 34867cc5b42..804fb6bb816 100644
--- a/kernel/exit.c
+++ b/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 * tsk)
struct mm_struct *mm = tsk->mm;
struct core_state *core_state;
- mm_release(tsk, mm);
if (!mm)
return;
/*
@@ -960,9 +960,13 @@ 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);
@@ -975,7 +979,6 @@ void do_exit(long code)
tty_audit_exit();
audit_free(tsk);
- tsk->exit_code = code;
taskstats_exit(tsk, group_dead);
exit_mm(tsk);