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From: Roland McGrath <roland@redhat.com>
To: Jakub Jelinek <jakub@redhat.com>
Cc: Ulrich Drepper <drepper@redhat.com>,
	Glibc hackers <libc-hacker@sources.redhat.com>
Subject: Re: [PATCH] sparc* bits/atomic.h
In-Reply-To: Jakub Jelinek's message of  Monday, 31 March 2003 00:44:05 +0200 <20030330224405.GA16629@sunsite.ms.mff.cuni.cz>
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> 2003-03-31  Jakub Jelinek  <jakub@redhat.com>
> 
> 	* sysdeps/sparc/sparc32/bits/atomic.h: New file.
> 	* sysdeps/sparc/sparc32/sparcv9/bits/atomic.h: New file.
> 	* sysdeps/sparc/sparc64/bits/atomic.h: New file.
> 
> 	* sysdeps/sparc/sparc32/atomicity.h: Removed.
> 	* sysdeps/sparc/sparc32/sparcv9/atomicity.h: Removed.
> 	* sysdeps/sparc/sparc64/atomicity.h: Removed.

Thanks, applied.

> sparc32 (not v9) lacks compare and swap, so it is implemented using
> test-and-set and a global lock. IMHO better than no locking at all,
> performance will suck as usually on those aging boxes.

Are there any actual MP boxes using those chips that Linux runs on?  If not
then you could use a software atomic sequence with kernel support like SH does.
e.g., the low bit of the thread register says to reload the PC from some
other register (and clear the flag bit).


Thanks,
Roland