On 2017/05/16 22:04:59 +0800, Junchang Wang wrote:
> Hi Paul and Akira,
>
> This is the updated patch according to the discussion with Akira and
> following is the summary. Please take a look. Comments are welcome!
>
> In function eventual( ), if the value of stopflag become larger than
> zero (the ''if'' branch is taken), then only the "eventual()" thread
> updates stopflag. So, the READ_ONCE() within the WRITE_ONCE() is not
> necessary. Remove it.
> In function count_cleanup( ), there is no need to run smp_mb( ) in
> between statement writing to and statement reading from the same
> variable, stopflag. Remove smp_mb().
>
>
> Thanks,
> --Jason
>
> On Tue, May 16, 2017 at 9:40 PM, Junchang Wang <junchangwang@xxxxxxxxx> wrote:
>> Signed-off-by: Junchang Wang <junchangwang@xxxxxxxxx>
>> Signed-off-by: Akira Yokosawa <akiyks@xxxxxxxxx>
Hi Jason,
Glad to know you agree with me here!
Can you resubmit a v2 of the patch to include the message above in the commit
log? It would be easier for Paul to apply.
Also, since I didn't created the patch itself, I'd like you to use the following
tag instead:
Suggested-by: Akira Yokosawa <akiyks@xxxxxxxxx>
in front of your Signed-off-by.
Thanks, Akira
>> ---
>> CodeSamples/count/count_stat_eventual.c | 8 ++++----
>> 1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/CodeSamples/count/count_stat_eventual.c b/CodeSamples/count/count_stat_eventual.c
>> index 464de30..1365168 100644
>> --- a/CodeSamples/count/count_stat_eventual.c
>> +++ b/CodeSamples/count/count_stat_eventual.c
>> @@ -40,16 +40,17 @@ void *eventual(void *arg)
>> {
>> int t;
>> unsigned long sum;
>> + int stopflag_l = 0;
>>
>> - while (READ_ONCE(stopflag) < 3) {
>> + while (stopflag_l < 3) {
>> sum = 0;
>> for_each_thread(t)
>> sum += READ_ONCE(per_thread(counter, t));
>> WRITE_ONCE(global_count, sum);
>> poll(NULL, 0, 1);
>> - if (READ_ONCE(stopflag)) {
>> + if ((stopflag_l = READ_ONCE(stopflag)) != 0) {
>> smp_mb();
>> - WRITE_ONCE(stopflag, READ_ONCE(stopflag) + 1);
>> + WRITE_ONCE(stopflag, ++stopflag_l);
>> }
>> }
>> return NULL;
>> @@ -68,7 +69,6 @@ void count_init(void)
>> void count_cleanup(void)
>> {
>> WRITE_ONCE(stopflag, 1);
>> - smp_mb();
>> while (READ_ONCE(stopflag) < 3)
>> poll(NULL, 0, 1);
>> smp_mb();
>> --
>> 2.7.4
>>
>
--
To unsubscribe from this list: send the line "unsubscribe perfbook" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
