From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1Cxnth-0003D9-Uy for qemu-devel@nongnu.org; Sun, 06 Feb 2005 10:00:26 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1Cxntf-0003CI-TB for qemu-devel@nongnu.org; Sun, 06 Feb 2005 10:00:24 -0500 Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Cxntf-0003Bi-QO for qemu-devel@nongnu.org; Sun, 06 Feb 2005 10:00:23 -0500 Received: from [65.74.133.9] (helo=mail.codesourcery.com) by monty-python.gnu.org with esmtp (TLSv1:DES-CBC3-SHA:168) (Exim 4.34) id 1CxndV-0002PH-Vp for qemu-devel@nongnu.org; Sun, 06 Feb 2005 09:43:42 -0500 From: Paul Brook Date: Sun, 6 Feb 2005 14:43:38 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200502061443.38384.paul@codesourcery.com> Subject: [Qemu-devel] testandset asm fix Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org The inline assembly used for the x86/x86-64 host testandset routine is bogus. The operand constraints are wrong (Fails to compile at -O0). Also the return value is incorrect. It should return 0 if the lock was successfully acquired. Patch below fixes it. The additional sete test is unnecessary, we can just use the comparison/writeback value. Paul Index: exec-all.h =================================================================== RCS file: /cvsroot/qemu/qemu/exec-all.h,v retrieving revision 1.26 diff -u -p -r1.26 exec-all.h --- exec-all.h 10 Jan 2005 23:23:48 -0000 1.26 +++ exec-all.h 6 Feb 2005 14:35:43 -0000 @@ -392,28 +392,24 @@ static inline int testandset (int *p) #ifdef __i386__ static inline int testandset (int *p) { - char ret; - long int readval; - - __asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0" - : "=q" (ret), "=m" (*p), "=a" (readval) - : "r" (1), "m" (*p), "a" (0) - : "memory"); - return ret; + long int readval = 0; + + __asm__ __volatile__ ("lock; cmpxchgl %2, %0" + : "+m" (*p), "+a" (readval) + : "r" (1)); + return readval; } #endif #ifdef __x86_64__ static inline int testandset (int *p) { - char ret; - int readval; - - __asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0" - : "=q" (ret), "=m" (*p), "=a" (readval) - : "r" (1), "m" (*p), "a" (0) - : "memory"); - return ret; + long int readval = 0; + + __asm__ __volatile__ ("lock; cmpxchgl %2, %0" + : "+m" (*p), "+a" (readval) + : "r" (1)); + return readval; } #endif