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authorKonstantin Khlebnikov <khlebnikov@openvz.org>2012-06-08 01:21:14 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2012-06-08 01:43:55 +0400
commit40af1bbdca47e5c8a2044039bb78ca8fd8b20f94 (patch)
tree70b5a21579f8b0137c09e54d523246d84be93430 /fs/exec.c
parent39caa0916ef27cf1da5026eb708a2b8413156f75 (diff)
downloadlinux-40af1bbdca47e5c8a2044039bb78ca8fd8b20f94.tar.xz
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 'fs/exec.c')
-rw-r--r--fs/exec.c1
1 files changed, 0 insertions, 1 deletions
diff --git a/fs/exec.c b/fs/exec.c
index a79786a8d2c8..b926ed19301e 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -819,7 +819,6 @@ 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) {