| From: | Neil Conway <neilc(at)samurai(dot)com> |
|---|---|
| To: | "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgreSQL(dot)org> |
| Subject: | Re: [COMMITTERS] pgsql: Do all accesses to shared buffer |
| Date: | 2005-10-21 21:43:49 |
| Message-ID: | 1129931029.19971.11.camel@localhost.localdomain |
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| Lists: | pgsql-committers pgsql-hackers |
On Mon, 2005-17-10 at 16:48 -0500, Jim C. Nasby wrote:
> Sorry if I'm just confused here, but don't LWLocks protect data
> structures susceptible to corruption? And if that's the case don't we
> need to be sure that the compiler can't optimize around them?
LWLocks certainly do protect shared data, and if the compiler rearranged
loads and stores around LWLocks acquire/release, it would result in
corruption. Tom was arguing it is unlikely the compiler will actually do
this (because LWLockAcquire is an out-of-line function call that might
invoke a system call, unlike SpinLockAcquire).
-Neil
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