Re: [PATCH] lockdep: annotate i386 apm

[Andrew Morton <akpm@osdl.org>]

On Thu, 12 Oct 2006 08:06:20 +0200
Peter Zijlstra <a.p.zijlstra@chello.nl> 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..

--- 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);
_

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