Re: Move PinBuffer and UnpinBuffer to atomics

On Tue, Mar 22, 2016 at 12:31 PM, Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:

> ! pg_atomic_write_u32(&bufHdr->state, state);
> } while (!StartBufferIO(bufHdr, true));
>
> Better Write some comment, about we clearing the BM_LOCKED from stage
> directly and need not to call UnlockBufHdr explicitly.
> otherwise its confusing.
>

Few more comments..

*** 828,837 ****
*/
do
{
! LockBufHdr(bufHdr);
*! Assert(bufHdr->flags & BM_VALID);*
! bufHdr->flags &= ~BM_VALID;
! UnlockBufHdr(bufHdr);
} while (!StartBufferIO(bufHdr, true));
}
}
--- 826,834 ----
*/
do
{
! uint32 state = LockBufHdr(bufHdr);
! state &= ~(BM_VALID | BM_LOCKED);
! pg_atomic_write_u32(&bufHdr->state, state);
} while (!StartBufferIO(bufHdr, true));

1. Previously there was a Assert, any reason why we removed it ?
Assert(bufHdr->flags & BM_VALID);

2. And also if we don't need assert then can't we directly clear BM_VALID
flag from state variable (if not locked) like pin/unpin buffer does,
without taking buffer header lock?

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com