From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Tue, 02 Oct 2007 15:22:28 +0100 (BST) Received: from mail.bawue.net ([193.7.176.63]:60909 "EHLO mail.bawue.net") by ftp.linux-mips.org with ESMTP id S20023830AbXJBOWS (ORCPT ); Tue, 2 Oct 2007 15:22:18 +0100 Received: from lagash (intrt.mips-uk.com [194.74.144.130]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.bawue.net (Postfix) with ESMTP id 86D80E0051; Tue, 2 Oct 2007 16:22:21 +0200 (CEST) Received: from ths by lagash with local (Exim 4.67) (envelope-from ) id 1IcidW-0003NT-Dg; Tue, 02 Oct 2007 15:22:10 +0100 Date: Tue, 2 Oct 2007 15:22:10 +0100 From: Thiemo Seufer To: Ralf Baechle Cc: Fuxin Zhang , linux-mips@linux-mips.org Subject: Re: cmpxchg broken in some situation Message-ID: <20071002142210.GD16772@networkno.de> References: <46FF7BC2.5050905@ict.ac.cn> <20071001025340.GA7091@linux-mips.org> <47010E15.7060109@ict.ac.cn> <20071001152620.GB15820@linux-mips.org> <470210B4.8020902@ict.ac.cn> <20071002103551.GB5152@linux-mips.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20071002103551.GB5152@linux-mips.org> User-Agent: Mutt/1.5.16 (2007-06-11) Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 16789 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: ths@networkno.de Precedence: bulk X-list: linux-mips Ralf Baechle wrote: > On Tue, Oct 02, 2007 at 05:34:44PM +0800, Fuxin Zhang wrote: > > > The problem is here: > > > > switch (sizeof(__ptr)) { // --> should be sizeof(*(__ptr)) > > case 4: > > ... > > Recompiling.. > > There was another small kink, cmpxchg_local() does not imply a memory > barrier so I optimized that case. > > And I don't complain about it being 151 lines shorter ;-) > > Ralf > > From: Ralf Baechle > > [MIPS] Typeproof reimplementation of cmpxchg. > > Signed-off-by: Ralf Baechle > > diff --git a/include/asm-mips/cmpxchg.h b/include/asm-mips/cmpxchg.h > new file mode 100644 > index 0000000..46bac47 > --- /dev/null > +++ b/include/asm-mips/cmpxchg.h > @@ -0,0 +1,107 @@ > +/* > + * This file is subject to the terms and conditions of the GNU General Public > + * License. See the file "COPYING" in the main directory of this archive > + * for more details. > + * > + * Copyright (C) 2003, 06, 07 by Ralf Baechle (ralf@linux-mips.org) > + */ > +#ifndef __ASM_CMPXCHG_H > +#define __ASM_CMPXCHG_H > + > +#include > + > +#define __HAVE_ARCH_CMPXCHG 1 > + > +#define __cmpxchg_asm(ld, st, m, old, new) \ > +({ \ > + __typeof(*(m)) __ret; \ > + \ > + if (cpu_has_llsc && R10000_LLSC_WAR) { \ > + __asm__ __volatile__( \ > + " .set push \n" \ > + " .set noat \n" \ > + " .set mips3 \n" \ > + "1: " ld " %0, %2 # __cmpxchg_u32 \n" \ > + " bne %0, %z3, 2f \n" \ > + " .set mips0 \n" \ > + " move $1, %z4 \n" \ > + " .set mips3 \n" \ > + " " st " $1, %1 \n" \ > + " beqzl $1, 1b \n" \ > + "2: \n" \ > + " .set pop \n" \ > + : "=&r" (__ret), "=R" (*m) \ > + : "R" (*m), "Jr" (old), "Jr" (new) \ > + : "memory"); \ > + } else if (cpu_has_llsc) { \ > + __asm__ __volatile__( \ > + " .set push \n" \ > + " .set noat \n" \ > + " .set mips3 \n" \ > + "1: " ld " %0, %2 # __cmpxchg_u32 \n" \ > + " bne %0, %z3, 2f \n" \ > + " .set mips0 \n" \ > + " move $1, %z4 \n" \ > + " .set mips3 \n" \ > + " " st " $1, %1 \n" \ > + " beqz $1, 3f \n" \ > + "2: \n" \ > + " .subsection 2 \n" \ > + "3: b 1b \n" \ > + " .previous \n" \ > + " .set pop \n" \ > + : "=&r" (__ret), "=R" (*m) \ > + : "R" (*m), "Jr" (old), "Jr" (new) \ > + : "memory"); \ > + } else { \ > + unsigned long __flags; \ > + \ > + raw_local_irq_save(__flags); \ > + __ret = *m; \ > + if (__ret == old) \ > + *m = new; \ > + raw_local_irq_restore(__flags); \ > + } \ > + \ > + smp_llsc_mb(); \ I think this line is surplus. > + \ > + __ret; \ > +}) > + > +/* > + * This function doesn't exist, so you'll get a linker error > + * if something tries to do an invalid cmpxchg(). > + */ > +extern void __cmpxchg_called_with_bad_pointer(void); > + > +#define __cmpxchg(ptr,old,new,barrier) \ > +({ \ > + __typeof__(ptr) __ptr = (ptr); \ > + __typeof__(*(ptr)) __old = (old); \ > + __typeof__(*(ptr)) __new = (new); \ > + __typeof__(*(ptr)) __res = 0; \ Maybe we need an acquire barrier here for some systems. > + switch (sizeof(*(__ptr))) { \ > + case 4: \ > + __res = __cmpxchg_asm("ll", "sc", __ptr, __old, __new); \ > + break; \ > + case 8: \ > + if (sizeof(long) == 8) { \ > + __res = __cmpxchg_asm("lld", "scd", __ptr, \ > + __old, __new); \ > + break; \ > + } \ > + default: \ > + __cmpxchg_called_with_bad_pointer(); \ > + break; \ > + } \ > + \ > + barrier; \ > + \ > + __res; \ > +}) > + > +#define cmpxchg(ptr, old, new) __cmpxchg(ptr, old, new, smp_llsc_mb()) > +#define cmpxchg_local(ptr, old, new) __cmpxchg(ptr, old, new,) > + > +#endif /* __ASM_CMPXCHG_H */ Thiemo