Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758607AbZAHNY7 (ORCPT ); Thu, 8 Jan 2009 08:24:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755604AbZAHNYu (ORCPT ); Thu, 8 Jan 2009 08:24:50 -0500 Received: from fg-out-1718.google.com ([72.14.220.158]:12262 "EHLO fg-out-1718.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755576AbZAHNYt (ORCPT ); Thu, 8 Jan 2009 08:24:49 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=bd6MR2GyCUcnI5fxKOCUsNF9xS4047I9Nl4dW5bLvOXZ6XiGPjnqJNI3e81VbSVCp0 gMVklCDlOjAtF9L8QWN8K+AcZXrrFr9LPsrpZTzMhF3QCjAe4XBL4Lj2AUvKKE62AS8r YnFX0JoRRzE1lBFmnC0zL/PKYS9Uvq5w5sjNY= Date: Thu, 8 Jan 2009 16:24:42 +0300 From: Cyrill Gorcunov To: Jiri Kosina Cc: Adam Osuchowski , linux-kernel@vger.kernel.org, Ingo Molnar , Nick Piggin Subject: Re: Is 386 processor still supported? Message-ID: <20090108132442.GB8015@localhost> References: <20090108120338.6b8b4567@zonk.pl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4010 Lines: 116 [Jiri Kosina - Thu, Jan 08, 2009 at 02:05:48PM +0100] | | [ CCs added ] | | On Thu, 8 Jan 2009, Adam Osuchowski wrote: | | > Recently, I found such piece of code in kernel 2.6.28 compiled for 386 | > processor: | > | > # grep M386 .config | > CONFIG_M386=y | > # objdump -d vmlinux | grep -A11 '<_spin_lock>:' | > c0321827 <_spin_lock>: | > c0321827: 89 e2 mov %esp,%edx | > c0321829: 81 e2 00 f0 ff ff and $0xfffff000,%edx | > c032182f: ff 42 14 incl 0x14(%edx) | > c0321832: ba 00 01 00 00 mov $0x100,%edx | > c0321837: f0 66 0f c1 10 lock xadd %dx,(%eax) | > c032183c: 38 f2 cmp %dh,%dl | > c032183e: 74 06 je c0321846 <_spin_lock+0x1f> | > c0321840: f3 90 pause | > c0321842: 8a 10 mov (%eax),%dl | > c0321844: eb f6 jmp c032183c <_spin_lock+0x15> | > c0321846: c3 ret | > | > But there is no xadd instruction on 386 processors. It is available on | > 486+ only. I have no chance to run this kernel on real 386 box, so I can't | > check it in practice, but I think it will not run. | > | > It is not compiler problem because it is explicitly written in assembly | > in __raw_spin_lock() function (include/asm-x86/spinlock.h) and there is | > no alternative code depending on CONFIG_M386. | | Hmm, this really looks like a bug to me. How about something like this | (untested). | | | From: Jiri Kosina | Subject: x86: make spinlocks available on machines without xadd insn | | Current kernel wouldn't compile on ancient x86 machines that don't support | xadd instruction, as ticket spinlocks implementation unconditionally uses | it. | | On machines without CONFIG_X86_XADD, use old-style byte spinlock | implementation instead. | | Reported-by: Adam Osuchowski | Signed-off-by: Jiri Kosina | | diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h | index d17c919..b3bc71b 100644 | --- a/arch/x86/include/asm/spinlock.h | +++ b/arch/x86/include/asm/spinlock.h | @@ -236,6 +236,40 @@ static inline void __byte_spin_unlock(raw_spinlock_t *lock) | bl->lock = 0; | } | #else /* !CONFIG_PARAVIRT */ | + | +/* old x86 machines do not have xadd insns, use old-style locks for them */ | +#ifndef CONFIG_X86_XADD | +static inline int __raw_spin_is_locked(raw_spinlock_t *lock) | +{ | + return __byte_spin_is_locked(lock); | +} | + | +static inline int __raw_spin_is_contended(raw_spinlock_t *lock) | +{ | + return __byte_spin_is_contended(lock); | +} | + | +static __always_inline void __raw_spin_lock(raw_spinlock_t *lock) | +{ | + __byte_spin_lock(lock); | +} | + | +static __always_inline int __raw_spin_trylock(raw_spinlock_t *lock) | +{ | + return __byte_spin_trylock(lock); | +} | + | +static __always_inline void __raw_spin_unlock(raw_spinlock_t *lock) | +{ | + __byte_spin_unlock(lock); | +} | + | +static __always_inline void __raw_spin_lock_flags(raw_spinlock_t *lock, | + unsigned long flags) | +{ | + __raw_spin_lock(lock); | +} | +#else /* CONFIG_X86_XADD */ | static inline int __raw_spin_is_locked(raw_spinlock_t *lock) | { | return __ticket_spin_is_locked(lock); | @@ -267,6 +301,7 @@ static __always_inline void __raw_spin_lock_flags(raw_spinlock_t *lock, | __raw_spin_lock(lock); | } | | +#endif /* CONFIG_X86_XADD */ | #endif /* CONFIG_PARAVIRT */ | | static inline void __raw_spin_unlock_wait(raw_spinlock_t *lock) | Jiri I could be wrong but it seems __byte_spin_lock is implemented under CONFIG_PARAVIRT and now referred under #else /* !CONFIG_PARAVIRT */ At least I didn'y found additional implementaion in tree. Did I miss anything? - Cyrill - -- 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/