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SubjectRe: [RFC PATCH 6/6] workqueue: use kmalloc_align() instead of hacking
On Tue, Mar 20, 2012 at 06:21:24PM +0800, Lai Jiangshan wrote:
> kmalloc_align() makes the code simpler.
>
> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> ---
> kernel/workqueue.c | 23 +++++------------------
> 1 files changed, 5 insertions(+), 18 deletions(-)
>
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index 5abf42f..beec5fd 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -2897,20 +2897,9 @@ static int alloc_cwqs(struct workqueue_struct *wq)
>
> if (!(wq->flags & WQ_UNBOUND))
> wq->cpu_wq.pcpu = __alloc_percpu(size, align);
> - else {
> - void *ptr;
> -
> - /*
> - * Allocate enough room to align cwq and put an extra
> - * pointer at the end pointing back to the originally
> - * allocated pointer which will be used for free.
> - */
> - ptr = kzalloc(size + align + sizeof(void *), GFP_KERNEL);
> - if (ptr) {
> - wq->cpu_wq.single = PTR_ALIGN(ptr, align);
> - *(void **)(wq->cpu_wq.single + 1) = ptr;
> - }
> - }
> + else
> + wq->cpu_wq.single = kmalloc_align(size,
> + GFP_KERNEL | __GFP_ZERO, align);
>
> /* just in case, make sure it's actually aligned */
> BUG_ON(!IS_ALIGNED(wq->cpu_wq.v, align));
> @@ -2921,10 +2910,8 @@ static void free_cwqs(struct workqueue_struct *wq)
> {
> if (!(wq->flags & WQ_UNBOUND))
> free_percpu(wq->cpu_wq.pcpu);
> - else if (wq->cpu_wq.single) {
> - /* the pointer to free is stored right after the cwq */
> - kfree(*(void **)(wq->cpu_wq.single + 1));
> - }
> + else if (wq->cpu_wq.single)
> + kfree(wq->cpu_wq.single);

Yes, this is hacky but I don't think building the whole
kmalloc_align() for only this is a good idea. If the open coded hack
bothers you just write a simplistic wrapper somewhere. We can make
that better integrated / more efficient when there are multiple users
of the interface, which I kinda doubt would happen. The reason why
cwq requiring larger alignment is more historic than anything else
after all.

Thanks.

--
tejun


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