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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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