---

yaml
---
r: 18511
b: refs/heads/master
c: 505970b
h: refs/heads/master
i:
  18509: 843eeec
  18507: 83c675c
  18503: 423b326
  18495: 2735ae9
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: ed68cb3676bb179768529aeb808403d57295af56
+refs/heads/master: 505970b96e3b7d22177c38e03435a68376628e7a

trunk/include/linux/cpuset.h

@@ -48,6 +48,9 @@ extern void __cpuset_memory_pressure_bump(void);
 extern struct file_operations proc_cpuset_operations;
 extern char *cpuset_task_status_allowed(struct task_struct *task, char *buffer);
 
+extern void cpuset_lock(void);
+extern void cpuset_unlock(void);
+
 #else /* !CONFIG_CPUSETS */
 
 static inline int cpuset_init_early(void) { return 0; }
@@ -93,6 +96,9 @@ static inline char *cpuset_task_status_allowed(struct task_struct *task,
 	return buffer;
 }
 
+static inline void cpuset_lock(void) {}
+static inline void cpuset_unlock(void) {}
+
 #endif /* !CONFIG_CPUSETS */
 
 #endif /* _LINUX_CPUSET_H */

trunk/kernel/cpuset.c

@@ -2149,6 +2149,33 @@ int __cpuset_zone_allowed(struct zone *z, gfp_t gfp_mask)
 	return allowed;
 }
 
+/**
+ * cpuset_lock - lock out any changes to cpuset structures
+ *
+ * The out of memory (oom) code needs to lock down cpusets
+ * from being changed while it scans the tasklist looking for a
+ * task in an overlapping cpuset.  Expose callback_sem via this
+ * cpuset_lock() routine, so the oom code can lock it, before
+ * locking the task list.  The tasklist_lock is a spinlock, so
+ * must be taken inside callback_sem.
+ */
+
+void cpuset_lock(void)
+{
+	down(&callback_sem);
+}
+
+/**
+ * cpuset_unlock - release lock on cpuset changes
+ *
+ * Undo the lock taken in a previous cpuset_lock() call.
+ */
+
+void cpuset_unlock(void)
+{
+	up(&callback_sem);
+}
+
 /**
  * cpuset_excl_nodes_overlap - Do we overlap @p's mem_exclusive ancestors?
  * @p: pointer to task_struct of some other task.
@@ -2158,16 +2185,14 @@ int __cpuset_zone_allowed(struct zone *z, gfp_t gfp_mask)
  * determine if task @p's memory usage might impact the memory
  * available to the current task.
  *
- * Acquires callback_sem - not suitable for calling from a fast path.
+ * Call while holding callback_sem.
  **/
 
 int cpuset_excl_nodes_overlap(const struct task_struct *p)
 {
 	const struct cpuset *cs1, *cs2;	/* my and p's cpuset ancestors */
 	int overlap = 0;		/* do cpusets overlap? */
 
-	down(&callback_sem);
-
 	task_lock(current);
 	if (current->flags & PF_EXITING) {
 		task_unlock(current);
@@ -2186,8 +2211,6 @@ int cpuset_excl_nodes_overlap(const struct task_struct *p)
 
 	overlap = nodes_intersects(cs1->mems_allowed, cs2->mems_allowed);
 done:
-	up(&callback_sem);
-
 	return overlap;
 }
 

trunk/mm/oom_kill.c

@@ -274,6 +274,7 @@ void out_of_memory(gfp_t gfp_mask, int order)
 		show_mem();
 	}
 
+	cpuset_lock();
 	read_lock(&tasklist_lock);
 retry:
 	p = select_bad_process();
@@ -284,6 +285,7 @@ void out_of_memory(gfp_t gfp_mask, int order)
 	/* Found nothing?!?! Either we hang forever, or we panic. */
 	if (!p) {
 		read_unlock(&tasklist_lock);
+		cpuset_unlock();
 		panic("Out of memory and no killable processes...\n");
 	}
 
@@ -293,6 +295,7 @@ void out_of_memory(gfp_t gfp_mask, int order)
 
  out:
 	read_unlock(&tasklist_lock);
+	cpuset_unlock();
 	if (mm)
 		mmput(mm);