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

> * 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 (;-)).

-dg

David Gould            dg@illustra.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.