On Tue, Aug 21, 2012 at 03:54:54PM -0500, Nathan Zimmer wrote:
> I am currently tracking a hotlock reported by a customer on a large, 512 cores,
> system, I am currently running 3.6.0 rc1 but the issue looks like it has been
> this way for a very long time.
> The offending lock is proc_dir_entry->pde_unload_lock.
>
> In proc_reg_release we are doing a kfree under the spinlock which is ok but it
> means we are holding the lock longer then required. Scaling improved when I
> moved kfree out.
It's OK to move it out.
Acked-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
> Also shouldn't the comment on pde_unload_lock also note that pde_openers and
> pde_unload_completion are both used under the lock?
Yeah, why not.
> --- a/fs/proc/inode.c
> +++ b/fs/proc/inode.c
> @@ -403,9 +403,11 @@ static int proc_reg_release(struct inode *inode, struct file *file)
> release = pde->proc_fops->release;
> if (pdeo) {
> list_del(&pdeo->lh);
> - kfree(pdeo);
> }
> spin_unlock(&pde->pde_unload_lock);
> + if (pdeo) {
> + kfree(pdeo);
> + }
>
> if (release)
> rv = release(inode, file);
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