On Mon, Apr 30, 2007 at 10:42:25PM +0530, Srivatsa Vaddagiri wrote:
> On Sun, Apr 29, 2007 at 02:37:21AM -0700, Paul Jackson wrote:
> > It builds and boots and mounts the cpuset file system ok.
> > But trying to write the 'mems' file hangs the system hard.
> 
> Basically we are attempting a read_lock(&tasklist_lock) in
> container_task_count() after taking write_lock_irq(&tasklist_lock) in
> update_nodemask()!
> 
> This patch seems to fix the prb for me:
> 
> 
> Fix write_lock() followed by read_lock() bug by introducing a 2nd
> argument to be passed into container_task_count. Other choice is to
> introduce a lock and unlocked versions of container_task_count() ..
> 
> Signed-off-by : Srivatsa Vaddagiri <[EMAIL PROTECTED]>

> -int container_task_count(const struct container *cont) {
> +int container_task_count(const struct container *cont, int take_lock) {
>       int count = 0;
>       struct task_struct *g, *p;
>       struct container_subsys_state *css;
>       int subsys_id;
>       get_first_subsys(cont, &css, &subsys_id);
>  
> -     read_lock(&tasklist_lock);
> +     if (take_lock)
> +             read_lock(&tasklist_lock);
>       do_each_thread(g, p) {
>               if (task_subsys_state(p, subsys_id) == css)
>                       count ++;
>       } while_each_thread(g, p);
> -     read_unlock(&tasklist_lock);
> +     if (take_lock)
> +             read_unlock(&tasklist_lock);
>       return count;

Umm, no - please naje two versions with and without the lock.  Also
Please fix up the codingstyle, the { belongs onto a line of it's own.


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