From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1CyA7V-0000ws-Er for qemu-devel@nongnu.org; Mon, 07 Feb 2005 09:44:09 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1CyA7O-0000ty-AD for qemu-devel@nongnu.org; Mon, 07 Feb 2005 09:44:07 -0500 Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1CyA7N-0000py-Ab for qemu-devel@nongnu.org; Mon, 07 Feb 2005 09:44:01 -0500 Received: from [64.233.184.197] (helo=wproxy.gmail.com) by monty-python.gnu.org with esmtp (Exim 4.34) id 1Cy9qW-0002py-TY for qemu-devel@nongnu.org; Mon, 07 Feb 2005 09:26:37 -0500 Received: by wproxy.gmail.com with SMTP id 70so1748235wra for ; Mon, 07 Feb 2005 06:26:36 -0800 (PST) Message-ID: Date: Mon, 7 Feb 2005 14:26:36 +0000 From: Piotras Subject: Re: [Qemu-devel] testandset asm fix In-Reply-To: <42077171.6030308@bellard.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit References: <200502061443.38384.paul@codesourcery.com> <42077171.6030308@bellard.org> Reply-To: Piotras , 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 What about IRQ latency? Piotrek On Mon, 07 Feb 2005 14:47:29 +0100, Fabrice Bellard wrote: > OK. Anyway, the locking in QEMU is mostly boggus. If SMP is implemented > someday with host threads, then it will be the right time to correct it ! > > Fabrice. > > Paul Brook wrote: > > 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 > > > > > > > > _______________________________________________ > > Qemu-devel mailing list > > Qemu-devel@nongnu.org > > http://lists.nongnu.org/mailman/listinfo/qemu-devel > > > > > > _______________________________________________ > Qemu-devel mailing list > Qemu-devel@nongnu.org > http://lists.nongnu.org/mailman/listinfo/qemu-devel >