Since mpol_put_task_policy() in do_exit() sets mempolicy = NULL,
mempolicy_nodemask_intersects() considers exited threads (e.g. a process
with dying leader and live threads) as eligible. But it is possible that
all of live threads are still ineligible.
Since has_intersects_mems_allowed() returns true as soon as one of threads
is considered eligible, mempolicy_nodemask_intersects() needs to consider
exited threads as ineligible. Since exit_mm() in do_exit() sets mm = NULL
before mpol_put_task_policy() sets mempolicy = NULL, we can exclude exited
threads by checking whether mm is NULL.
While at it, since mempolicy_nodemask_intersects() is called by only
has_intersects_mems_allowed(), it is guaranteed that mask != NULL.
BTW, are there processes where some of threads use MPOL_{BIND,INTERLEAVE}
and the rest do not use MPOL_{BIND,INTERLEAVE} ? If no, we can use
find_lock_task_mm() instead of for_each_thread() for mask != NULL case
in has_intersects_mems_allowed().
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
mm/mempolicy.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 01600d8..938f0a0 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1974,11 +1974,10 @@ bool mempolicy_nodemask_intersects(struct task_struct *tsk,
const nodemask_t *mask)
{
struct mempolicy *mempolicy;
- bool ret = true;
+ bool ret;
- if (!mask)
- return ret;
task_lock(tsk);
+ ret = tsk->mm;
mempolicy = tsk->mempolicy;
if (!mempolicy)
goto out;
--
1.8.3.1
