From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Snook Subject: [PATCH 21/24] make atomic_read() behave consistently on v850 Date: Thu, 9 Aug 2007 10:16:36 -0400 Message-ID: <20070809141636.GA18860@shell.boston.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii 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 To: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, torvalds@linux-foundation.org Return-path: Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org From: Chris Snook Make atomic_read() volatile on v850. 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 --- linux-2.6.23-rc2-orig/include/asm-v850/atomic.h 2007-07-08 19:32:17.000000000 -0400 +++ linux-2.6.23-rc2/include/asm-v850/atomic.h 2007-08-09 07:50:15.000000000 -0400 @@ -27,7 +27,11 @@ typedef struct { int counter; } atomic_t #ifdef __KERNEL__ -#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 int atomic_add_return (int i, volatile atomic_t *v)