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Re: [HACKERS] Re: [PATCHES] patches for 6.2.1p6

From: dg(at)illustra(dot)com (David Gould)
To: tih(at)Hamartun(dot)Priv(dot)NO (Tom Ivar Helbekkmo)
Cc: maillist(at)candle(dot)pha(dot)pa(dot)us, scrappy(at)hub(dot)org, dz(at)cs(dot)unitn(dot)it, hackers(at)postgreSQL(dot)org
Subject: Re: [HACKERS] Re: [PATCHES] patches for 6.2.1p6
Date: 1998-03-18 23:51:51
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
> * Bruce Momjian
> | Just a warning that this is not going to be easy.  We have OS-specific
> | code for spinlocks in include/storage/s_lock.h and
> | backend/storage/buffer/s_lock.c.  So each S_LOCK macro call has to have
> | its test-and-set logic de-coupled with its while-lock-fail-try-again
> | logic.  Most of them are easy, but some like VAX:
> | 
> | #define S_LOCK(addr)        __asm__("1: bbssi $0,(%0),1b": :"r"(addr))
> | 
> | are hard to de-couple.  Now, I did not know we supported NetBSD on VAX. 
> | Does it work, anyone?  Can I remove it?
> Yes, it works.  No, please don't break it.  Heck, I only just got it
> in in time for 6.3!  :-) The not-so-busy-waiting-spinlock stuff can be
> put in on a platform at a time -- I'll expand the VAX version to do
> the right thing once someone has done another platform, so I can see
> what's the preferred way of doing it.
> -tih

I won't. I hope.

Seriously, if you want to, please create a function to emulate the following:

 * tas(lock)
 * Access to platform specific test_and_set functionality. Given pointer to
 * lock attempts to acquire the lock atomically.
 * Returns 0 for success, nonzero for failure.
typedef slock_t unsigned char;		/* or whatever works on the platform */

int tas(slock_t *lock)
    slock_t	tmp;

    /* atomic, interlocked */
    tmp = *lock;
    *lock = -1; 			/* any nonzero will do here */

    return (tmp != 0);

Given this, I can fold the VAX right into the grand scheme, just like a
normal computer (;-)).


David Gould            dg(at)illustra(dot)com           510.628.3783 or 510.305.9468 
Informix Software  (No, really)         300 Lakeside Drive  Oakland, CA 94612
 - I realize now that irony has no place in business communications.

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