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Date: Wed, 11 Oct 2006 23:39:25 -0700
From: Andrew Morton <akpm@...l.org>
To: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: linux-kernel <linux-kernel@...r.kernel.org>, sfr@...b.auug.org.au,
Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] lockdep: annotate i386 apm
On Thu, 12 Oct 2006 08:06:20 +0200
Peter Zijlstra <a.p.zijlstra@...llo.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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