From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jiri Gaisler Date: Wed, 22 Dec 2010 09:51:05 +0000 Subject: Re: SPARC32 SMP IRQ15 question Message-Id: <4D11CA09.60106@gaisler.com> List-Id: References: <4D0A2102.8030100@gaisler.com> In-Reply-To: <4D0A2102.8030100@gaisler.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: sparclinux@vger.kernel.org Alex Buell wrote: > On Tue, 2010-12-21 at 19:54 -0800, David Miller wrote: >>> We are thinking of switching the LEON port to use CASA (compare and >> swap), just like in the sparc64 port. Most newer leon3/4 processors >> implement CASA, even if the instruction belongs to sparc V9 and not >> V8. Would a patch like that be accepted (for the LEON port only)? This >> will not fix the SMP for general sparc32 (which really is broken), but >> it would fix it for LEON. >> >> It should be fine as long as the patches are clean enough. > > Rather than specialising it for LEON, why not just test for CASA > availability and use it if it available? The CASA is only necessary for SMP systems, as the current irq15 solution will NOT work on sparc32-SMP. So falling back on irq15 when CASA is not present is not really an option, as it will lead to a deadlock sooner or later ...