{
bool need_loop;
-repeat:
/*
* Allow tasks that have access to memory reserves because they have
* been OOM killed to get memory anywhere.
*/
need_loop = task_has_mempolicy(tsk) ||
!nodes_intersects(*newmems, tsk->mems_allowed);
- nodes_or(tsk->mems_allowed, tsk->mems_allowed, *newmems);
- mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP1);
- /*
- * ensure checking ->mems_allowed_change_disable after setting all new
- * allowed nodes.
- *
- * the read-side task can see an nodemask with new allowed nodes and
- * old allowed nodes. and if it allocates page when cpuset clears newly
- * disallowed ones continuous, it can see the new allowed bits.
- *
- * And if setting all new allowed nodes is after the checking, setting
- * all new allowed nodes and clearing newly disallowed ones will be done
- * continuous, and the read-side task may find no node to alloc page.
- */
- smp_mb();
+ if (need_loop)
+ write_seqcount_begin(&tsk->mems_allowed_seq);
- /*
- * Allocation of memory is very fast, we needn't sleep when waiting
- * for the read-side.
- */
- while (need_loop && ACCESS_ONCE(tsk->mems_allowed_change_disable)) {
- task_unlock(tsk);
- if (!task_curr(tsk))
- yield();
- goto repeat;
- }
-
- /*
- * ensure checking ->mems_allowed_change_disable before clearing all new
- * disallowed nodes.
- *
- * if clearing newly disallowed bits before the checking, the read-side
- * task may find no node to alloc page.
- */
- smp_mb();
+ nodes_or(tsk->mems_allowed, tsk->mems_allowed, *newmems);
+ mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP1);
mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP2);
tsk->mems_allowed = *newmems;
+
+ if (need_loop)
+ write_seqcount_end(&tsk->mems_allowed_seq);
+
task_unlock(tsk);
}