Re: Fix spinlock usage in UnpinBuffer()

Qingqing Zhou <zhouqq(at)cs(dot)toronto(dot)edu> writes:
> Remove SpinLockAcquire_NoHoldoff() and related. Now SpinLockAcquire() will
> not holdoff cancle/die interrupts. This will give cleaner and clearer
> useage of spinlock and also save a few cycles.

Applied with some minor comment updates.

I noticed that shmem.c holds ShmemIndexLock considerably longer than any
other spinlock is held, and across operations that could theoretically
fail (hashtable manipulations). This doesn't matter a lot in the Unix
code because only the postmaster ever executes ShmemInitStruct, but
in the Windows port we run that code every time a backend is launched.
I think that we could convert that spinlock to an LWLock. Will look into it.

regards, tom lane