Re: Condition variable live lock

Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> writes:
> On Mon, Jan 8, 2018 at 12:38 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Concretely, as per attached.

> +1 for the idea. Haven't looked at the code yet but I'll review this
> and the proclist patch shortly.

Thanks. BTW, I realized that there is a second (and perhaps more
important) reason why we can only prepare one CV sleep at a time:
we only have one cvWaitLink in our PGPROC. So I'm now inclined
to word the revised comment in ConditionVariablePrepareToSleep as

/*
* If some other sleep is already prepared, cancel it; this is necessary
* because we have just one static variable tracking the prepared sleep,
* and also only one cvWaitLink in our PGPROC. It's okay to do this
* because whenever control does return to the other test-and-sleep loop,
* its ConditionVariableSleep call will just re-establish that sleep as
* the prepared one.
*/

regards, tom lane