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SubjectRe: [PATCH] lockdep: annotate i386 apm
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On Wed, 2006-10-11 at 14:18 -0700, Andrew Morton wrote:
> On Wed, 11 Oct 2006 15:40:22 +0200
> Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
>
> >
> > Lockdep doesn't like to enable interrupts when they are enabled already.
> >
> > ...
> >
> > --- linux-2.6.18.noarch.orig/arch/i386/kernel/apm.c
> > +++ linux-2.6.18.noarch/arch/i386/kernel/apm.c
> > @@ -539,11 +539,22 @@ 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();
> > +#define APM_DO_CLI \
> > + do { \
> > + if (apm_info.allow_ints) { \
> > + if (irqs_disabled_flags(flags)) \
> > + local_irq_enable(); \
> > + } else \
> > + local_irq_disable(); \
> > + } while (0)
> > +
> > +#define APM_DO_STI \
> > + do { \
> > + if (irqs_disabled_flags(flags)) \
> > + local_irq_disable(); \
> > + else if (irqs_disabled()) \
> > + local_irq_enable(); \
> > + } while (0)
> >
> > #ifdef APM_ZERO_SEGS
> > # define APM_DECL_SEGS \
> > @@ -600,7 +611,7 @@ static u8 apm_bios_call(u32 func, u32 eb
> > 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);
> > + APM_DO_STI;
> > gdt[0x40 / 8] = save_desc_40;
> > put_cpu();
> > apm_restore_cpus(cpus);
> > @@ -644,7 +655,7 @@ static u8 apm_bios_call_simple(u32 func,
> > APM_DO_SAVE_SEGS;
> > error = apm_bios_call_simple_asm(func, ebx_in, ecx_in, eax);
> > APM_DO_RESTORE_SEGS;
> > - local_irq_restore(flags);
> > + APM_DO_STI;
> > gdt[0x40 / 8] = save_desc_40;
> > put_cpu();
> > apm_restore_cpus(cpus);
>
> ick.
>
> Does this work?
>
> --- 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;
> @@ -596,8 +590,9 @@ 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;
> + local_irq_save(flags);
> + if (apm_info.allow_ints)
> + local_irq_enable();
> APM_DO_SAVE_SEGS;
> apm_bios_call_asm(func, ebx_in, ecx_in, eax, ebx, ecx, edx, esi);
> APM_DO_RESTORE_SEGS;
> @@ -640,8 +635,9 @@ 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;
> + local_irq_save(flags);
> + if (apm_info.allow_ints)
> + local_irq_enable();
> APM_DO_SAVE_SEGS;
> error = apm_bios_call_simple_asm(func, ebx_in, ecx_in, eax);
> APM_DO_RESTORE_SEGS;
> _

#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!




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