Re: USE_BARRIER_SMGRRELEASE on Linux?

On Tue, Feb 15, 2022 at 10:57:32PM -0800, Nathan Bossart wrote:
> On Tue, Feb 15, 2022 at 10:14:04PM -0800, Nathan Bossart wrote:
>> It looks like register_unlink_segment() is called prior to the checkpoint,
>> but the checkpointer is not calling RememberSyncRequest() until after
>> SyncPreCheckpoint(). This means that the requests are registered with the
>> next checkpoint cycle count, so they aren't processed until the next
>> checkpoint.
>
> Calling AbsorbSyncRequests() before advancing the checkpoint cycle counter
> seems to fix the issue. However, this requires moving SyncPreCheckpoint()
> out of the critical section in CreateCheckPoint(). Patch attached.

An alternative fix might be to call AbsorbSyncRequests() after increasing
the ckpt_started counter in CheckpointerMain(). AFAICT there is a window
just before checkpointing where new requests are registered for the
checkpoint following the one about to begin.

--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com