Re: shared-memory based stats collector

On 2020-Mar-27, Kyotaro Horiguchi wrote:

> +/*
> + * XLogArchiveWakeupEnd - Set up archiver wakeup stuff
> + */
> +void
> +XLogArchiveWakeupStart(void)
> +{
> +    Latch *old_latch PG_USED_FOR_ASSERTS_ONLY;
> +
> +    SpinLockAcquire(&XLogCtl->info_lck);
> +    old_latch = XLogCtl->archiverWakeupLatch;
> +    XLogCtl->archiverWakeupLatch = MyLatch;
> +    SpinLockRelease(&XLogCtl->info_lck);
> +    Assert (old_latch == NULL);
> +}

Comment is wrong about the function name; OTOH I don't think the
old_latch assigment in the fourth line won't work well in non-assert
builds.  But why do you need those shenanigans?  Surely
"Assert(XLogCtl->archiverWakeupLatch == NULL)" in the locked region
before assigning MyLatch should be sufficient and acceptable?

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
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