[PATCH] synchronize_irq needs a barrier
[Posted October 23, 2007 by corbet]
| From: |
| Benjamin Herrenschmidt <benh-AT-kernel.crashing.org> |
| To: |
| Linus Torvalds <torvalds-AT-linux-foundation.org> |
| Subject: |
| [PATCH] synchronize_irq needs a barrier |
| Date: |
| Thu, 18 Oct 2007 11:25:42 +1000 |
| Message-ID: |
| <1192670742.12879.5.camel@pasglop> |
| Cc: |
| akpm <akpm-AT-linux-foundation.org>,
Linux Kernel list <linux-kernel-AT-vger.kernel.org>,
linuxppc-dev list <linuxppc-dev-AT-ozlabs.org> |
| Archive‑link: | |
Article |
synchronize_irq needs at the very least a compiler barrier and a
read barrier on SMP, but there are enough cases around where a
write barrier is also needed and it's not a hot path so I prefer
using a full smp_mb() here.
It will degrade to a compiler barrier on !SMP.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
Index: linux-work/kernel/irq/manage.c
===================================================================
--- linux-work.orig/kernel/irq/manage.c 2007-10-18 11:22:16.000000000 +1000
+++ linux-work/kernel/irq/manage.c 2007-10-18 11:22:20.000000000 +1000
@@ -33,6 +33,7 @@ void synchronize_irq(unsigned int irq)
if (irq >= NR_IRQS)
return;
+ smp_mb();
while (desc->status & IRQ_INPROGRESS)
cpu_relax();
}
