2009-03-12 17:46:22

by Dhaval Giani

Subject: cpuset: Check if the cpus allowed is a subset of the cpuset's cpus for PF_THREAD_BOUND threads

When a kernel thread which has been bound to a CPU is moved to
a cpuset which is a superset of the CPU it is bound to, the
movement fails.

[root@llm11 cgroups]# mkdir a
[root@llm11 cgroups]# echo 3 > a/cpuset.cpus
[root@llm11 cgroups]# echo 0 > a/cpuset.mems
[root@llm11 cgroups]# echo 12 > a/tasks
[root@llm11 cgroups]# echo 12 > tasks
-bash: echo: write error: Invalid argument
[root@llm11 cgroups]# cat cpuset.cpus
0-7
[root@llm11 cgroups]#

(pid 12 is the migration thread bound to CPU 3)

Change the check to see if the cpus allowed is a subset of the
cpus allowed for that cpuset.

Signed-off-by: Dhaval Giani <[email protected]>
---
kernel/cpuset.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1362,7 +1362,7 @@ static int cpuset_can_attach(struct cgro

if (tsk->flags & PF_THREAD_BOUND) {
mutex_lock(&callback_mutex);
- if (!cpumask_equal(&tsk->cpus_allowed, cs->cpus_allowed))
+ if (!cpumask_subset(&tsk->cpus_allowed, cs->cpus_allowed))
ret = -EINVAL;
mutex_unlock(&callback_mutex);
}
--
regards,
Dhaval

2009-03-13 00:08:50

by Dhaval Giani

Subject: [tip:sched/urgent] cpuset: Check if the cpus allowed is a subset of the cpuset's cpus for PF_THREAD_BOUND threads

Commit-ID: 5a98d36112f4301f068b638d6e0db2357f7deb75
Gitweb: http://git.kernel.org/tip/5a98d36112f4301f068b638d6e0db2357f7deb75
Author: Dhaval Giani <[email protected]>
AuthorDate: Thu, 12 Mar 2009 23:15:01 +0530
Commit: Ingo Molnar <[email protected]>
CommitDate: Fri, 13 Mar 2009 00:21:25 +0100

cpuset: Check if the cpus allowed is a subset of the cpuset's cpus for PF_THREAD_BOUND threads

When a kernel thread which has been bound to a CPU is moved to
a cpuset which is a superset of the CPU it is bound to, the
movement fails.

[root@llm11 cgroups]# mkdir a
[root@llm11 cgroups]# echo 3 > a/cpuset.cpus
[root@llm11 cgroups]# echo 0 > a/cpuset.mems
[root@llm11 cgroups]# echo 12 > a/tasks
[root@llm11 cgroups]# echo 12 > tasks
-bash: echo: write error: Invalid argument
[root@llm11 cgroups]# cat cpuset.cpus
0-7
[root@llm11 cgroups]#

(pid 12 is the migration thread bound to CPU 3)

Change the check to see if the cpus allowed is a subset of the
cpus allowed for that cpuset.

Signed-off-by: Dhaval Giani <[email protected]>
Cc: Balbir Singh <[email protected]>
Cc: Srivatsa Vaddagiri <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: [email protected]
LKML-Reference: <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>


---
kernel/cpuset.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index f76db9d..34cfd46 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1362,7 +1362,7 @@ static int cpuset_can_attach(struct cgroup_subsys *ss,

if (tsk->flags & PF_THREAD_BOUND) {
mutex_lock(&callback_mutex);
- if (!cpumask_equal(&tsk->cpus_allowed, cs->cpus_allowed))
+ if (!cpumask_subset(&tsk->cpus_allowed, cs->cpus_allowed))
ret = -EINVAL;
mutex_unlock(&callback_mutex);
}

2009-03-13 01:33:25

by Ingo Molnar

Subject: Re: [tip:sched/urgent] cpuset: Check if the cpus allowed is a subset of the cpuset's cpus for PF_THREAD_BOUND threads

* Dhaval Giani <[email protected]> wrote:

> Commit-ID: 5a98d36112f4301f068b638d6e0db2357f7deb75
> Gitweb: http://git.kernel.org/tip/5a98d36112f4301f068b638d6e0db2357f7deb75
> Author: Dhaval Giani <[email protected]>
> AuthorDate: Thu, 12 Mar 2009 23:15:01 +0530
> Commit: Ingo Molnar <[email protected]>
> CommitDate: Fri, 13 Mar 2009 00:21:25 +0100
>
> cpuset: Check if the cpus allowed is a subset of the cpuset's
> cpus for PF_THREAD_BOUND threads

Dropped this patch for now - Andrew says it got NAK-ed and he's
handling it with other fixes.

Ingo

2009-03-13 01:43:54

by Li Zefan

Subject: Re: [tip:sched/urgent] cpuset: Check if the cpus allowed is a subset of the cpuset's cpus for PF_THREAD_BOUND threads

CC: David Rientjes <[email protected]>

Ingo Molnar wrote:
> * Dhaval Giani <[email protected]> wrote:
>
>> Commit-ID: 5a98d36112f4301f068b638d6e0db2357f7deb75
>> Gitweb: http://git.kernel.org/tip/5a98d36112f4301f068b638d6e0db2357f7deb75
>> Author: Dhaval Giani <[email protected]>
>> AuthorDate: Thu, 12 Mar 2009 23:15:01 +0530
>> Commit: Ingo Molnar <[email protected]>
>> CommitDate: Fri, 13 Mar 2009 00:21:25 +0100
>>
>> cpuset: Check if the cpus allowed is a subset of the cpuset's
>> cpus for PF_THREAD_BOUND threads
>
> Dropped this patch for now - Andrew says it got NAK-ed and he's
> handling it with other fixes.
>

It's not a bug, it's David Rientjes that introduced this behavior:
9985b0bab332289f14837eff3c6e0bcc658b58f7

And here was the discussion:
http://lkml.org/lkml/2008/6/5/310