From: Chris Snook <csnook@redhat.com>
To: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
torvalds@linux-foundation.org
Cc: netdev@vger.kernel.org, akpm@linux-foundation.org, ak@suse.de,
heiko.carstens@de.ibm.com, davem@davemloft.net,
schwidefsky@de.ibm.com, wensong@linux-vs.org, horms@verge.net.au,
wjiang@resilience.com, cfriesen@nortel.com, zlynx@acm.org,
rpjday@mindspring.com, jesper.juhl@gmail.com
Subject: [PATCH 4/24] make atomic_read() behave consistently on blackfin
Date: Thu, 9 Aug 2007 09:37:03 -0400 [thread overview]
Message-ID: <20070809133703.GA14317@shell.boston.redhat.com> (raw)
From: Chris Snook <csnook@redhat.com>
Make atomic_read() volatile on blackfin. This ensures that busy-waiting
for an interrupt handler to change an atomic_t won't get compiled to an
infinite loop, consistent with SMP architectures.
Signed-off-by: Chris Snook <csnook@redhat.com>
--- linux-2.6.23-rc2-orig/include/asm-blackfin/atomic.h 2007-07-08 19:32:17.000000000 -0400
+++ linux-2.6.23-rc2/include/asm-blackfin/atomic.h 2007-08-09 06:36:15.000000000 -0400
@@ -18,7 +18,11 @@ typedef struct {
} atomic_t;
#define ATOMIC_INIT(i) { (i) }
-#define atomic_read(v) ((v)->counter)
+/*
+ * Casting to volatile here minimizes the need for barriers,
+ * without having to declare the type itself as volatile.
+ */
+#define atomic_read(v) (*(volatile int *)&(v)->counter)
#define atomic_set(v, i) (((v)->counter) = i)
static __inline__ void atomic_add(int i, atomic_t * v)
reply other threads:[~2007-08-09 13:38 UTC|newest]
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