Re: Condition variable live lock

On Mon, Jan 8, 2018 at 5:25 PM, Thomas Munro
<thomas(dot)munro(at)enterprisedb(dot)com> wrote:
> On Sun, Jan 7, 2018 at 10:43 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Actually ... perhaps a better design would be to have
>> ConditionVariable[PrepareTo]Sleep auto-cancel any prepared sleep for
>> a different condition variable, analogously to what we just did in
>> ConditionVariableBroadcast, on the same theory that whenever control
>> returns to the other CV wait loop it can re-establish the relevant
>> state easily enough. I have to think that if the use of CVs grows
>> much, the existing restriction is going to become untenable anyway,
>> so why not just get rid of it?
>
> +1
>
> It's a more robust API this way.

One very small thing after another look:

- Assert(cv_sleep_target == NULL);
+ if (cv_sleep_target != NULL)
+ ConditionVariableCancelSleep();

The test for cv_sleep_target != NULL is redundant since
ConditionVariableCancelSleep() would return early.
ConditionVariableBroadcast() doesn't do that.

--
Thomas Munro
http://www.enterprisedb.com