Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752194Ab1C1GMk (ORCPT ); Mon, 28 Mar 2011 02:12:40 -0400 Received: from courier.cs.helsinki.fi ([128.214.9.1]:56303 "EHLO mail.cs.helsinki.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751857Ab1C1GM0 (ORCPT ); Mon, 28 Mar 2011 02:12:26 -0400 Message-ID: <4D9026C8.6060905@cs.helsinki.fi> Date: Mon, 28 Mar 2011 09:12:24 +0300 From: Pekka Enberg User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.2.15) Gecko/20110303 Thunderbird/3.1.9 MIME-Version: 1.0 To: Christoph Lameter CC: Linus Torvalds , Eric Dumazet , Ingo Molnar , Thomas Gleixner , akpm@linux-foundation.org, tj@kernel.org, npiggin@kernel.dk, rientjes@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, tj@kernel.org Subject: Re: [PATCH] slub: Disable the lockless allocator References: <20110324142146.GA11682@elte.hu> <20110324172653.GA28507@elte.hu> <20110324185258.GA28370@elte.hu> <20110324192247.GA5477@elte.hu> <20110326112725.GA28612@elte.hu> <20110326114736.GA8251@elte.hu> <1301161507.2979.105.camel@edumazet-laptop> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3438 Lines: 108 On 3/27/11 4:57 AM, Christoph Lameter wrote: > But then the same fix must also be used in the asm code or the fallback > (turns out that the fallback is always used in kmem_cache_init since > the instruction patching comes later). > > Patch boots fine both in UP and SMP mode > > > > > Subject: percpu: Omit segment prefix in the UP case for cmpxchg_double > > Omit the segment prefix in the UP case. GS is not used then > and we will generate segfaults if cmpxchg16b is used otherwise. > > Signed-off-by: Linus Torvalds > Signed-off-by: Christoph Lameter > > arch/x86/include/asm/percpu.h | 10 ++++++---- > 1 files changed, 6 insertions(+), 4 deletions(-) > > Index: linux-2.6/arch/x86/include/asm/percpu.h > =================================================================== > --- linux-2.6.orig/arch/x86/include/asm/percpu.h 2011-03-26 20:43:03.994089001 -0500 > +++ linux-2.6/arch/x86/include/asm/percpu.h 2011-03-26 20:43:22.414089004 -0500 > @@ -45,7 +45,7 @@ > #include > > #ifdef CONFIG_SMP > -#define __percpu_arg(x) "%%"__stringify(__percpu_seg)":%P" #x > +#define __percpu_prefix "%%"__stringify(__percpu_seg)":" > #define __my_cpu_offset percpu_read(this_cpu_off) > > /* > @@ -62,9 +62,11 @@ > (typeof(*(ptr)) __kernel __force *)tcp_ptr__; \ > }) > #else > -#define __percpu_arg(x) "%P" #x > +#define __percpu_prefix "" > #endif > > +#define __percpu_arg(x) __percpu_prefix "%P" #x > + > /* > * Initialized pointers to per-cpu variables needed for the boot > * processor need to use these macros to get the proper address > @@ -516,11 +518,11 @@ > typeof(o2) __n2 = n2; \ > typeof(o2) __dummy; \ > alternative_io("call this_cpu_cmpxchg16b_emu\n\t" P6_NOP4, \ > - "cmpxchg16b %%gs:(%%rsi)\n\tsetz %0\n\t", \ > + "cmpxchg16b " __percpu_prefix "(%%rsi)\n\tsetz %0\n\t", \ > X86_FEATURE_CX16, \ > ASM_OUTPUT2("=a"(__ret), "=d"(__dummy)), \ > "S" (&pcp1), "b"(__n1), "c"(__n2), \ > - "a"(__o1), "d"(__o2)); \ > + "a"(__o1), "d"(__o2) : "memory"); \ > __ret; \ > }) > > Index: linux-2.6/arch/x86/lib/cmpxchg16b_emu.S > =================================================================== > --- linux-2.6.orig/arch/x86/lib/cmpxchg16b_emu.S 2011-03-26 20:43:57.384089004 -0500 > +++ linux-2.6/arch/x86/lib/cmpxchg16b_emu.S 2011-03-26 20:48:42.684088999 -0500 > @@ -10,6 +10,12 @@ > #include > #include > > +#ifdef CONFIG_SMP > +#define SEG_PREFIX %gs: > +#else > +#define SEG_PREFIX > +#endif > + > .text > > /* > @@ -37,13 +43,13 @@ > pushf > cli > > - cmpq %gs:(%rsi), %rax > + cmpq SEG_PREFIX(%rsi), %rax > jne not_same > - cmpq %gs:8(%rsi), %rdx > + cmpq SEG_PREFIX 8(%rsi), %rdx > jne not_same > > - movq %rbx, %gs:(%rsi) > - movq %rcx, %gs:8(%rsi) > + movq %rbx, SEG_PREFIX(%rsi) > + movq %rcx, SEG_PREFIX 8(%rsi) > > popf > mov $1, %al Tejun, does this look good to you as well? I think it should go through the percpu tree. It's needed to fix a boot crash with lockless SLUB fastpaths enabled. Pekka -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/