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[PATCH] cpuset: avoid changing cpuset's cpus when -errno returned

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[view original message]
From: Li Zefan
Subject: [PATCH] cpuset: avoid changing cpuset's cpus when -errno returned
Date: Wednesday, September 3, 2008 - 12:33 am

After the patch:

commit 0b2f630a28d53b5a2082a5275bc3334b10373508
Author: Miao Xie <miaox@cn.fujitsu.com>
Date:   Fri Jul 25 01:47:21 2008 -0700

    cpusets: restructure the function update_cpumask() and update_nodemask()

It might happen that 'echo 0 > /cpuset/sub/cpus' returns failure but 'cpus'
has been changed, because cpus was changed before calling heap_init() which
may return -ENOMEM.

This patch restores the orginal behavior.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
 kernel/cpuset.c |   32 ++++++++++++++------------------
 1 files changed, 14 insertions(+), 18 deletions(-)

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index d5ab79c..817f8ac 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -774,36 +774,27 @@ static void cpuset_change_cpumask(struct task_struct *tsk,
 /**
  * update_tasks_cpumask - Update the cpumasks of tasks in the cpuset.
  * @cs: the cpuset in which each task's cpus_allowed mask needs to be changed
+ * @heap: if NULL, defer allocating heap memory to cgroup_scan_tasks()
  *
  * Called with cgroup_mutex held
  *
  * The cgroup_scan_tasks() function will scan all the tasks in a cgroup,
  * calling callback functions for each.
  *
- * Return 0 if successful, -errno if not.
+ * Always return 0 if @heap != NULL, may return -errno if @heap == NULL
  */
-static int update_tasks_cpumask(struct cpuset *cs)
+static int update_tasks_cpumask(struct cpuset *cs, struct ptr_heap *heap)
 {
 	struct cgroup_scanner scan;
-	struct ptr_heap heap;
 	int retval;
 
-	/*
-	 * cgroup_scan_tasks() will initialize heap->gt for us.
-	 * heap_init() is still needed here for we should not change
-	 * cs->cpus_allowed when heap_init() fails.
-	 */
-	retval = heap_init(&heap, PAGE_SIZE, GFP_KERNEL, NULL);
-	if (retval)
-		return retval;
-
 	scan.cg = cs->css.cgroup;
 	scan.test_task = cpuset_test_cpumask;
 	scan.process_task = cpuset_change_cpumask;
-	scan.heap = &heap;
+	scan.heap = heap;
 	retval = cgroup_scan_tasks(&scan);
+	BUG_ON(heap ...
[ message continues ]
[view original message]
From: Paul Menage
Subject: Re: [PATCH] cpuset: avoid changing cpuset's cpus when -errno returned
Date: Thursday, September 4, 2008 - 10:49 am

Since neither of the callers of update_tasks_cpumask() check the
return value (one knows it's going to be 0, the other doesn't care
about errors) I think it would be better to just make it a void
function.

Paul
--


[ message continues ]
[view original message]
From: Li Zefan
Subject: [PATCH -v2] cpuset: avoid changing cpuset's cpus when -errno returned
Date: Thursday, September 4, 2008 - 8:42 pm

After the patch:

commit 0b2f630a28d53b5a2082a5275bc3334b10373508
Author: Miao Xie <miaox@cn.fujitsu.com>
Date:   Fri Jul 25 01:47:21 2008 -0700

    cpusets: restructure the function update_cpumask() and update_nodemask()

It might happen that 'echo 0 > /cpuset/sub/cpus' returned failure but 'cpus'
has been changed, because cpus was changed before calling heap_init() which
may return -ENOMEM.

This patch restores the orginal behavior.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
 kernel/cpuset.c |   37 +++++++++++++++----------------------
 1 files changed, 15 insertions(+), 22 deletions(-)

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index d5ab79c..0d33827 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -774,37 +774,25 @@ static void cpuset_change_cpumask(struct task_struct *tsk,
 /**
  * update_tasks_cpumask - Update the cpumasks of tasks in the cpuset.
  * @cs: the cpuset in which each task's cpus_allowed mask needs to be changed
+ * @heap: if NULL, defer allocating heap memory to cgroup_scan_tasks()
  *
  * Called with cgroup_mutex held
  *
  * The cgroup_scan_tasks() function will scan all the tasks in a cgroup,
  * calling callback functions for each.
  *
- * Return 0 if successful, -errno if not.
+ * No return value. It's guaranteed that cgroup_scan_tasks() always returns 0
+ * if @heap != NULL.
  */
-static int update_tasks_cpumask(struct cpuset *cs)
+static void update_tasks_cpumask(struct cpuset *cs, struct ptr_heap *heap)
 {
 	struct cgroup_scanner scan;
-	struct ptr_heap heap;
-	int retval;
-
-	/*
-	 * cgroup_scan_tasks() will initialize heap->gt for us.
-	 * heap_init() is still needed here for we should not change
-	 * cs->cpus_allowed when heap_init() fails.
-	 */
-	retval = heap_init(&heap, PAGE_SIZE, GFP_KERNEL, NULL);
-	if (retval)
-		return retval;
 
 	scan.cg = cs->css.cgroup;
 	scan.test_task = cpuset_test_cpumask;
 	scan.process_task = cpuset_change_cpumask;
-	scan.heap = &heap;
-	retval = ...
[ message continues ]
[view original message]
From: Paul Menage
Subject: Re: [PATCH -v2] cpuset: avoid changing cpuset's cpus when -errno returned
Date: Friday, September 5, 2008 - 4:24 pm

Acked-by: Paul Menage <menage@google.com>

Thanks.

--


[ message continues ]
Previous thread: [patch 5/8] m68k: Remove unused atari_kbd_translate() by Geert Uytterhoeven on Wednesday, September 3, 2008 - 12:15 am. (4 messages)

Next thread: [alsa-devel][PATCH] add the nvidia HDMI codec driver for MCP77/79 by peerchen on Wednesday, September 3, 2008 - 12:58 am. (7 messages)