The patch titled
From: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx>
has been added to the -mm tree. Its filename is
mm-correctly-synchronize-rss-counters-at-exit-exec.patch
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------------------------------------------------------
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.
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 | 9 +++++----
kernel/fork.c | 8 ++++++++
3 files changed, 13 insertions(+), 5 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 +959,10 @@ 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);
+
+ /* 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);
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
@@ -780,6 +780,14 @@ void mm_release(struct task_struct *tsk,
}
tsk->clear_child_tid = NULL;
}
+
+ /*
+ * Final rss-counter synchronization. After this point must be
+ * no page-faults into this mm from current context, otherwise
+ * mm->rss_stat will be inconsistent.
+ */
+ if (mm)
+ sync_mm_rss(mm);
}
/*
_
Subject: From: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx>
Patches currently in -mm which might be from khlebnikov@xxxxxxxxxx are
linux-next.patch
mm-correctly-synchronize-rss-counters-at-exit-exec.patch
mm-correctly-synchronize-rss-counters-at-exit-exec-fix.patch
mm-vmscan-remove-lumpy-reclaim.patch
mm-vmscan-remove-reclaim_mode_t.patch
mm-fix-page-faults-detection-in-swap-token-logic.patch
mm-memcg-scanning_global_lru-means-mem_cgroup_disabled.patch
mm-memcg-move-reclaim_stat-into-lruvec.patch
mm-push-lru-index-into-shrink_active_list.patch
mm-push-lru-index-into-shrink_active_list-fix.patch
mm-mark-mm-inline-functions-as-__always_inline.patch
mm-remove-lru-type-checks-from-__isolate_lru_page.patch
mm-memcg-kill-mem_cgroup_lru_del.patch
mm-memcg-use-vm_swappiness-from-target-memory-cgroup.patch
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