Re: [PATCH v4 02/17] sched_clock: Use seqcount instead of rollingour own

[Will Deacon]

On Fri, Jul 19, 2013 at 12:21:15AM +0100, Stephen Boyd wrote:
> We're going to increase the cyc value to 64 bits in the near
> future. Doing that is going to break the custom seqcount
> implementation in the sched_clock code because 64 bit numbers
> aren't guaranteed to be atomic. Replace the cyc_copy with a
> seqcount to avoid this problem.
> 
> Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
> Signed-off-by: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
> ---
>  kernel/time/sched_clock.c | 27 ++++++++-------------------
>  1 file changed, 8 insertions(+), 19 deletions(-)

Looks good to me. The current scheme would be very fiddly to extend to
64-bit values on 32-bit architectures without cheap atomic doubleword
accesses.

Acked-by: Will Deacon <will.deacon@xxxxxxx>

Will
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