From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755529AbYHMUoR (ORCPT ); Wed, 13 Aug 2008 16:44:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753414AbYHMUno (ORCPT ); Wed, 13 Aug 2008 16:43:44 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:53818 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753115AbYHMUnn (ORCPT ); Wed, 13 Aug 2008 16:43:43 -0400 Date: Wed, 13 Aug 2008 13:41:18 -0700 From: Andrew Morton To: Linus Torvalds Cc: ebiederm@xmission.com, ying.huang@intel.com, pavel@ucw.cz, nigel@nigel.suspend2.net, rjw@sisk.pl, vgoyal@redhat.com, mingo@elte.hu, linux-kernel@vger.kernel.org, kexec@lists.infradead.org Subject: Re: [PATCH] kexec jump: fix compiling warning on xchg(&kexec_lock, 0) in kernel_kexec() Message-Id: <20080813134118.e1ab1292.akpm@linux-foundation.org> In-Reply-To: References: <1218618760.24951.137.camel@caritas-dev.intel.com> <20080813124406.21091eae.akpm@linux-foundation.org> <20080813130749.c406ab6c.akpm@linux-foundation.org> <20080813132535.6cd4bab6.akpm@linux-foundation.org> X-Mailer: Sylpheed version 2.2.4 (GTK+ 2.8.20; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 13 Aug 2008 13:31:24 -0700 (PDT) Linus Torvalds wrote: > On Wed, 13 Aug 2008, Andrew Morton wrote: > > > > #2: > > I thought you said there were things that want to sleep in the region? be reasonable - that was over five minutes ago. --- a/kernel/kexec.c~kexec-use-a-bitop-for-locking-rather-than-xchg +++ a/kernel/kexec.c @@ -12,7 +12,7 @@ #include #include #include -#include +#include #include #include #include @@ -924,19 +924,14 @@ static int kimage_load_segment(struct ki */ struct kimage *kexec_image; struct kimage *kexec_crash_image; -/* - * A home grown binary mutex. - * Nothing can wait so this mutex is safe to use - * in interrupt context :) - */ -static int kexec_lock; + +static DEFINE_MUTEX(kexec_mutex); asmlinkage long sys_kexec_load(unsigned long entry, unsigned long nr_segments, struct kexec_segment __user *segments, unsigned long flags) { struct kimage **dest_image, *image; - int locked; int result; /* We only trust the superuser with rebooting the system. */ @@ -972,8 +967,7 @@ asmlinkage long sys_kexec_load(unsigned * * KISS: always take the mutex. */ - locked = xchg(&kexec_lock, 1); - if (locked) + if (!mutex_trylock(&kexec_mutex)) return -EBUSY; dest_image = &kexec_image; @@ -1015,8 +1009,7 @@ asmlinkage long sys_kexec_load(unsigned image = xchg(dest_image, image); out: - locked = xchg(&kexec_lock, 0); /* Release the mutex */ - BUG_ON(!locked); + mutex_unlock(&kexec_mutex); kimage_free(image); return result; @@ -1063,10 +1056,7 @@ asmlinkage long compat_sys_kexec_load(un void crash_kexec(struct pt_regs *regs) { - int locked; - - - /* Take the kexec_lock here to prevent sys_kexec_load + /* Take the kexec_mutex here to prevent sys_kexec_load * running on one cpu from replacing the crash kernel * we are using after a panic on a different cpu. * @@ -1074,8 +1064,7 @@ void crash_kexec(struct pt_regs *regs) * of memory the xchg(&kexec_crash_image) would be * sufficient. But since I reuse the memory... */ - locked = xchg(&kexec_lock, 1); - if (!locked) { + if (mutex_trylock(&kexec_mutex)) { if (kexec_crash_image) { struct pt_regs fixed_regs; crash_setup_regs(&fixed_regs, regs); @@ -1083,8 +1072,7 @@ void crash_kexec(struct pt_regs *regs) machine_crash_shutdown(&fixed_regs); machine_kexec(kexec_crash_image); } - locked = xchg(&kexec_lock, 0); - BUG_ON(!locked); + mutex_unlock(&kexec_mutex); } } @@ -1434,7 +1422,7 @@ int kernel_kexec(void) { int error = 0; - if (xchg(&kexec_lock, 1)) + if (!mutex_trylock(&kexec_mutex)) return -EBUSY; if (!kexec_image) { error = -EINVAL; @@ -1498,8 +1486,6 @@ int kernel_kexec(void) #endif Unlock: - if (!xchg(&kexec_lock, 0)) - BUG(); - + mutex_unlock(&kexec_mutex); return error; } _