Revert "mm: correctly synchronize rss-counters at exit/exec"
This reverts commit 40af1bbdca47e5c8a2044039bb78ca8fd8b20f94.
It's horribly and utterly broken for at least the following reasons:
- calling sync_mm_rss() from mmput() is fundamentally wrong, because
there's absolutely no reason to believe that the task that does the
mmput() always does it on its own VM. Example: fork, ptrace, /proc -
you name it.
- calling it *after* having done mmdrop() on it is doubly insane, since
the mm struct may well be gone now.
- testing mm against NULL before you call it is insane too, since a
NULL mm there would have caused oopses long before.
.. and those are just the three bugs I found before I decided to give up
looking for me and revert it asap. I should have caught it before I
even took it, but I trusted Andrew too much.
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/exec.c b/fs/exec.c
index b926ed1..a79786a 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -819,6 +819,7 @@
/* 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 --git a/kernel/exit.c b/kernel/exit.c
index 804fb6b..34867cc 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -423,7 +423,6 @@
* 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
@@ -641,6 +640,7 @@
struct mm_struct *mm = tsk->mm;
struct core_state *core_state;
+ mm_release(tsk, mm);
if (!mm)
return;
/*
@@ -960,13 +960,9 @@
preempt_count());
acct_update_integrals(tsk);
-
- /* 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);
-
+ /* sync mm's RSS info before statistics gathering */
+ if (tsk->mm)
+ sync_mm_rss(tsk->mm);
group_dead = atomic_dec_and_test(&tsk->signal->live);
if (group_dead) {
hrtimer_cancel(&tsk->signal->real_timer);
@@ -979,6 +975,7 @@
tty_audit_exit();
audit_free(tsk);
+ tsk->exit_code = code;
taskstats_exit(tsk, group_dead);
exit_mm(tsk);
diff --git a/kernel/fork.c b/kernel/fork.c
index 0560781..ab5211b 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -619,14 +619,6 @@
module_put(mm->binfmt->module);
mmdrop(mm);
}
-
- /*
- * 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);
}
EXPORT_SYMBOL_GPL(mmput);