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authorLinus Torvalds <torvalds@linux-foundation.org>2012-06-07 17:54:07 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-06-07 17:54:07 -0700
commit48d212a2eecaca2e1875925837ad27b2f43f48a3 (patch)
treefbd83c7b15856971f6d7297e1d23dc862ba2989c
parent46edaedaf3842164281d0f86c41bc152f4b4d32e (diff)
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>
-rw-r--r--fs/exec.c1
-rw-r--r--kernel/exit.c13
-rw-r--r--kernel/fork.c8
3 files changed, 6 insertions, 16 deletions
diff --git a/fs/exec.c b/fs/exec.c
index b926ed19301..a79786a8d2c 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -819,6 +819,7 @@ static int exec_mmap(struct mm_struct *mm)
/* 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 804fb6bb816..34867cc5b42 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -423,7 +423,6 @@ 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
@@ -641,6 +640,7 @@ 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;
/*
@@ -960,13 +960,9 @@ void do_exit(long code)
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 @@ void do_exit(long code)
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 0560781c690..ab5211b9e62 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -619,14 +619,6 @@ void mmput(struct mm_struct *mm)
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);