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SubjectRe: [PATCH 3/6] cpuset: convert cpuset_attach() to use cpumask_var_t
On Mon, 05 Jan 2009 16:47:21 +0800 Li Zefan <lizf@cn.fujitsu.com> wrote:

> Allocate a global cpumask_var_t at boot, and use it in cpuset_attach(), so
> we won't fail cpuset_attach().
>
> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
> Acked-by: Mike Travis <travis@sgi.com>
> ---
> kernel/cpuset.c | 14 +++++++++-----
> 1 files changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/cpuset.c b/kernel/cpuset.c
> index afa29cf..1e32e6b 100644
> --- a/kernel/cpuset.c
> +++ b/kernel/cpuset.c
> @@ -1306,6 +1306,9 @@ static int fmeter_getrate(struct fmeter *fmp)
> return val;
> }
>
> +/* Protected by cgroup_lock */
> +static cpumask_var_t cpus_attach;
> +
> /* Called by cgroups to determine if a cpuset is usable; cgroup_mutex held */
> static int cpuset_can_attach(struct cgroup_subsys *ss,
> struct cgroup *cont, struct task_struct *tsk)
> @@ -1330,7 +1333,6 @@ static void cpuset_attach(struct cgroup_subsys *ss,
> struct cgroup *cont, struct cgroup *oldcont,
> struct task_struct *tsk)
> {
> - cpumask_t cpus;
> nodemask_t from, to;
> struct mm_struct *mm;
> struct cpuset *cs = cgroup_cs(cont);
> @@ -1338,13 +1340,13 @@ static void cpuset_attach(struct cgroup_subsys *ss,
> int err;
>
> if (cs == &top_cpuset) {
> - cpus = cpu_possible_map;
> + cpumask_copy(cpus_attach, cpu_possible_mask);
> } else {
> mutex_lock(&callback_mutex);
> - guarantee_online_cpus(cs, &cpus);
> + guarantee_online_cpus(cs, cpus_attach);
> mutex_unlock(&callback_mutex);
> }
> - err = set_cpus_allowed_ptr(tsk, &cpus);
> + err = set_cpus_allowed_ptr(tsk, cpus_attach);
> if (err)
> return;
>
> @@ -1357,7 +1359,6 @@ static void cpuset_attach(struct cgroup_subsys *ss,
> cpuset_migrate_mm(mm, &from, &to);
> mmput(mm);
> }
> -
> }
>
> /* The various types of files and directories in a cpuset file system */
> @@ -1838,6 +1839,9 @@ int __init cpuset_init(void)
> if (err < 0)
> return err;
>
> + if (!alloc_cpumask_var(&cpus_attach, GFP_KERNEL))
> + BUG();
> +
> number_of_cpusets = 1;
> return 0;
> }

OK, that works.

Do we need to dynamically allocate cpus_attach? Can we just do

static cpumask_t cpus_attach;

?


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