From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161231AbWJLGuk (ORCPT ); Thu, 12 Oct 2006 02:50:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161247AbWJLGuj (ORCPT ); Thu, 12 Oct 2006 02:50:39 -0400 Received: from amsfep17-int.chello.nl ([213.46.243.15]:10789 "EHLO amsfep18-int.chello.nl") by vger.kernel.org with ESMTP id S1161231AbWJLGuj (ORCPT ); Thu, 12 Oct 2006 02:50:39 -0400 Subject: Re: [PATCH] lockdep: annotate i386 apm From: Peter Zijlstra To: Andrew Morton Cc: linux-kernel , sfr@canb.auug.org.au, Ingo Molnar In-Reply-To: <20061011233925.c9ba117a.akpm@osdl.org> References: <1160574022.2006.82.camel@taijtu> <20061011141813.79fb278f.akpm@osdl.org> <1160633180.2006.94.camel@taijtu> <20061011233925.c9ba117a.akpm@osdl.org> Content-Type: text/plain Date: Thu, 12 Oct 2006 08:50:50 +0200 Message-Id: <1160635850.2006.98.camel@taijtu> Mime-Version: 1.0 X-Mailer: Evolution 2.6.3 (2.6.3-1.fc5.5) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2006-10-11 at 23:39 -0700, Andrew Morton wrote: > On Thu, 12 Oct 2006 08:06:20 +0200 > Peter Zijlstra wrote: > > > #define local_irq_restore(flags) \ > > do { \ > > if (raw_irqs_disabled_flags(flags)) { \ > > raw_local_irq_restore(flags); \ > > trace_hardirqs_off(); \ > > } else { \ > > trace_hardirqs_on(); \ > > raw_local_irq_restore(flags); \ > > } \ > > } while (0) > > > > So, say interrupts were enabled when entering apm_bios_call*(); you now > > save that in flags, disable interrupts, and enable them again. > > Upon reaching local_irq_restore(), we'll hit the else branch with irq's > > enabled and call trace_hardirqs_on(), which goes EEEK! > > I'd assumed lockdep was less stupid than that ;) This? Seems a bit > overdone.. Seems simple enough, bit on the verbose side, _however_ it depends on the BIOS call not changing the irq state. I don't know about BIOSs but I thought the general consensus was to distrust them. Was my original _that_ hard to read? > --- a/arch/i386/kernel/apm.c~lockdep-annotate-i386-apm > +++ a/arch/i386/kernel/apm.c > @@ -540,12 +540,6 @@ static inline void apm_restore_cpus(cpum > * Also, we KNOW that for the non error case of apm_bios_call, there > * is no useful data returned in the low order 8 bits of eax. > */ > -#define APM_DO_CLI \ > - if (apm_info.allow_ints) \ > - local_irq_enable(); \ > - else \ > - local_irq_disable(); > - > #ifdef APM_ZERO_SEGS > # define APM_DECL_SEGS \ > unsigned int saved_fs; unsigned int saved_gs; > @@ -583,11 +577,12 @@ static u8 apm_bios_call(u32 func, u32 eb > u32 *eax, u32 *ebx, u32 *ecx, u32 *edx, u32 *esi) > { > APM_DECL_SEGS > - unsigned long flags; > cpumask_t cpus; > int cpu; > struct desc_struct save_desc_40; > struct desc_struct *gdt; > + int enable_irqs = 0; > + int disable_irqs = 0; > > cpus = apm_save_cpus(); > > @@ -596,12 +591,26 @@ static u8 apm_bios_call(u32 func, u32 eb > save_desc_40 = gdt[0x40 / 8]; > gdt[0x40 / 8] = bad_bios_desc; > > - local_save_flags(flags); > - APM_DO_CLI; > + if (apm_info.allow_ints) { > + if (irqs_disabled()) { > + local_irq_enable(); > + disable_irqs = 1; > + } > + } else { > + if (!irqs_disabled()) { > + local_irq_disable(); > + enable_irqs = 1; > + } > + } > + > + > APM_DO_SAVE_SEGS; > apm_bios_call_asm(func, ebx_in, ecx_in, eax, ebx, ecx, edx, esi); > APM_DO_RESTORE_SEGS; > - local_irq_restore(flags); > + if (disable_irqs) > + local_irq_disable(); > + if (enable_irqs) > + local_irq_enable(); > gdt[0x40 / 8] = save_desc_40; > put_cpu(); > apm_restore_cpus(cpus); > @@ -627,11 +636,12 @@ static u8 apm_bios_call_simple(u32 func, > { > u8 error; > APM_DECL_SEGS > - unsigned long flags; > cpumask_t cpus; > int cpu; > struct desc_struct save_desc_40; > struct desc_struct *gdt; > + int enable_irqs = 0; > + int disable_irqs = 0; > > cpus = apm_save_cpus(); > > @@ -640,12 +650,25 @@ static u8 apm_bios_call_simple(u32 func, > save_desc_40 = gdt[0x40 / 8]; > gdt[0x40 / 8] = bad_bios_desc; > > - local_save_flags(flags); > - APM_DO_CLI; > + if (apm_info.allow_ints) { > + if (irqs_disabled()) { > + local_irq_enable(); > + disable_irqs = 1; > + } > + } else { > + if (!irqs_disabled()) { > + local_irq_disable(); > + enable_irqs = 1; > + } > + } > + > APM_DO_SAVE_SEGS; > error = apm_bios_call_simple_asm(func, ebx_in, ecx_in, eax); > APM_DO_RESTORE_SEGS; > - local_irq_restore(flags); > + if (disable_irqs) > + local_irq_disable(); > + if (enable_irqs) > + local_irq_enable(); > gdt[0x40 / 8] = save_desc_40; > put_cpu(); > apm_restore_cpus(cpus); > _ >