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SubjectRe: [PATCH] smp: kill unnecessary variable - csd_flags
On Mon, Jul 29, 2013 at 10:29:45AM +0800, Xie XiuQi wrote:
> We used csd_flags formerly because we allocated csd_data by
> kmalloc when "wait == 0". When fail to allocation, we will
> fall back to on-stack allocation. "csd_data" might be invalid
> after generic_exec_single return.
>
> But now we use per cpu data for single cpu ipi calls, and
> csd_data can't fall back to on-stack allocation when "wait == 0".
>
> So csd_flags is unnecessary now. Remove it.

The much simpler argument is that both callsites of
generic_exec_single() do an unconditional csd_lock().

> Signed-off-by: Xie XiuQi <xiexiuqi@huawei.com>
> ---
> kernel/smp.c | 11 +----------
> 1 files changed, 1 insertions(+), 10 deletions(-)
>
> diff --git a/kernel/smp.c b/kernel/smp.c
> index 4dba0f7..cac2b6e 100644
> --- a/kernel/smp.c
> +++ b/kernel/smp.c
> @@ -186,25 +186,16 @@ void generic_smp_call_function_single_interrupt(void)
>
> while (!list_empty(&list)) {
> struct call_single_data *csd;
> - unsigned int csd_flags;
>
> csd = list_entry(list.next, struct call_single_data, list);
> list_del(&csd->list);
>
> - /*
> - * 'csd' can be invalid after this call if flags == 0
> - * (when called through generic_exec_single()),
> - * so save them away before making the call:
> - */
> - csd_flags = csd->flags;
> -
> csd->func(csd->info);
>
> /*
> * Unlocked CSDs are valid through generic_exec_single():
> */
> - if (csd_flags & CSD_FLAG_LOCK)
> - csd_unlock(csd);
> + csd_unlock(csd);

The comment is completely useless and confusing after this; why do you
leave it in?


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