From 058a401be3656dbefb6ac81e08a254ab56f066a0 Mon Sep 17 00:00:00 2001
From: Paul Jackson <pj@sgi.com>
Date: Sat, 14 Jan 2006 13:21:06 -0800
Subject: [PATCH] --- yaml --- r: 18511 b: refs/heads/master c:
 505970b96e3b7d22177c38e03435a68376628e7a h: refs/heads/master i:   18509:
 843eeeced0426800732e5e6ef7d857a7d25dc635   18507:
 83c675cd261a7dcac64e485264245e1a6007ea31   18503:
 423b326a10ba92050df22056b5859ccd1a1907fe   18495:
 2735ae9e8db0b41f89e732a4cc42399f08f48ce2 v: v3

---
 [refs]                       |  2 +-
 trunk/include/linux/cpuset.h |  6 ++++++
 trunk/kernel/cpuset.c        | 33 ++++++++++++++++++++++++++++-----
 trunk/mm/oom_kill.c          |  3 +++
 4 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/[refs] b/[refs]
index 872992a42b8c..77f664f25503 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: ed68cb3676bb179768529aeb808403d57295af56
+refs/heads/master: 505970b96e3b7d22177c38e03435a68376628e7a
diff --git a/trunk/include/linux/cpuset.h b/trunk/include/linux/cpuset.h
index c472f972bd6d..3bc606927116 100644
--- a/trunk/include/linux/cpuset.h
+++ b/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 */
diff --git a/trunk/kernel/cpuset.c b/trunk/kernel/cpuset.c
index d4b6bd7d74e5..fe2f71f92ae0 100644
--- a/trunk/kernel/cpuset.c
+++ b/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.
@@ -2158,7 +2185,7 @@ 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)
@@ -2166,8 +2193,6 @@ 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;
 }
 
diff --git a/trunk/mm/oom_kill.c b/trunk/mm/oom_kill.c
index 4748b906aff2..14bd4ec79597 100644
--- a/trunk/mm/oom_kill.c
+++ b/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);