[PATCH] linux-2.6.0-test2_mtrr-race-fix_A0

[Mark Haverkamp <markh@osdl.org>]

On Wed, 2003-08-06 at 11:02, john stultz wrote:
> On Wed, 2003-08-06 at 11:05, Mark Haverkamp wrote:
> > On Wed, 2003-08-06 at 10:15, john stultz wrote:
> > > 
> > > Well, let me look at it again and see if I can come up with a proper
> > > fix. 
> > I added an extra sync up from the caller after the last gate change so
> > it is the last one to touch the automatic data.
> 
> Ah, you beat me to it! 
> 
> I'm actually testing the very same change (comments differ a touch, but
> that's ok).
> 
> Looks good. If everyone is happy I'd say resubmit it to Andrew.
> 
> thanks
> -john

I'd like to submit this patch for inclusion.  It adds an extra sync up
in set_mtrr and ipi_handler to make sure that set_mtrr is the last to
touch the automatic set_mtrr_data.


===== arch/i386/kernel/cpu/mtrr/main.c 1.29 vs edited =====
--- 1.29/arch/i386/kernel/cpu/mtrr/main.c	Tue Jul 15 10:08:48 2003
+++ edited/arch/i386/kernel/cpu/mtrr/main.c	Wed Aug  6 10:46:00 2003
@@ -169,6 +169,7 @@
 		cpu_relax();
 		barrier();
 	}
+	atomic_dec(&data->count);
 	local_irq_restore(flags);
 }
 
@@ -256,8 +257,18 @@
 		cpu_relax();
 		barrier();
 	}
-	local_irq_restore(flags);
+	atomic_set(&data.count, num_booting_cpus() - 1);
 	atomic_set(&data.gate,0);
+
+	/* 
+	 * Wait here for everyone to have seen the gate change
+	 * So we're the last ones to touch 'data'
+	 */
+	while(atomic_read(&data.count)) {
+		cpu_relax();
+		barrier();
+	}
+	local_irq_restore(flags);
 }
 
 /**


-- 
Mark Haverkamp <markh@osdl.org>