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SubjectRe: [PATCH v2 1/3] hrtimer: add hrtimer_init_cpu()
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I'm rather sure Thomas would want to know about this..


On Wed, 2012-09-12 at 16:13 +0200, Stephane Eranian wrote:
> hrtimer_init() assumes it is called for the current CPU
> as it accesses per-cpu variables (hrtimer_bases).
>
> However, there can be cases where a hrtimer is initialized
> from a different CPU, so add an entry point to make this
> more explicit.
>
> Signed-off-by: Stephane Eranian <eranian@google.com>
> ---
> include/linux/hrtimer.h | 3 +++
> kernel/hrtimer.c | 17 ++++++++++++-----
> 2 files changed, 15 insertions(+), 5 deletions(-)
>

> +static void __hrtimer_init(int cpu, struct hrtimer *timer, clockid_t clock_id,
> enum hrtimer_mode mode)
> {
> struct hrtimer_cpu_base *cpu_base;
> @@ -1154,7 +1154,7 @@ static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
>
> memset(timer, 0, sizeof(struct hrtimer));
>
> - cpu_base = &__raw_get_cpu_var(hrtimer_bases);
> + cpu_base = &per_cpu(hrtimer_bases, cpu);
>
> if (clock_id == CLOCK_REALTIME && mode != HRTIMER_MODE_ABS)
> clock_id = CLOCK_MONOTONIC;


I don't see the point, one of the first things
__hrtimer_start_range_ns() does is switch_hrtimer_base() to swizzle it
to the calling CPUs base.

And since all the perf event rotation muck is strictly per cpu that all
should work out just fine, no?


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