[PATCH] lockdep: annotate i386 apm

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

Ok, so how about this:

---
Lockdep doesn't like to enable interrupts when they are enabled already.

BUG: warning at kernel/lockdep.c:1814/trace_hardirqs_on() (Not tainted)
 [<c04051ed>] show_trace_log_lvl+0x58/0x16a
 [<c04057fa>] show_trace+0xd/0x10
 [<c0405913>] dump_stack+0x19/0x1b
 [<c043abfb>] trace_hardirqs_on+0xa2/0x11e
 [<c041463c>] apm_bios_call_simple+0xcd/0xfd
 [<c0415242>] apm+0x92/0x5b1
 [<c0402005>] kernel_thread_helper+0x5/0xb
DWARF2 unwinder stuck at kernel_thread_helper+0x5/0xb
Leftover inexact backtrace:
 [<c04057fa>] show_trace+0xd/0x10
 [<c0405913>] dump_stack+0x19/0x1b
 [<c043abfb>] trace_hardirqs_on+0xa2/0x11e
 [<c041463c>] apm_bios_call_simple+0xcd/0xfd
 [<c0415242>] apm+0x92/0x5b1
 [<c0402005>] kernel_thread_helper+0x5/0xb

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 arch/i386/kernel/apm.c |   37 +++++++++++++++++++++++++++----------
 1 file changed, 27 insertions(+), 10 deletions(-)

Index: linux-2.6.18.noarch/arch/i386/kernel/apm.c
===================================================================
--- linux-2.6.18.noarch.orig/arch/i386/kernel/apm.c
+++ linux-2.6.18.noarch/arch/i386/kernel/apm.c
@@ -539,11 +539,30 @@ 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 \
+
+static inline unsigned long __apm_irq_save(void)
+{
+	unsigned long flags;
+	local_save_flags(flags);
+	if (apm_info.allow_ints) {
+		if (irqs_disabled_flags(flags))
+			local_irq_enable();
+	} else
+		local_irq_disable();
+
+	return flags;
+}
+
+#define apm_irq_save(flags) \
+	do { flags = __apm_irq_save(); } while (0)
+
+static inline void apm_irq_restore(unsigned long flags)
+{
+	if (irqs_disabled_flags(flags))
 		local_irq_disable();
+	else if (irqs_disabled())
+		local_irq_enable();
+}
 
 #ifdef APM_ZERO_SEGS
 #	define APM_DECL_SEGS \
@@ -595,12 +614,11 @@ 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;
+	apm_irq_save(flags);
 	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_irq_restore(flags);
 	gdt[0x40 / 8] = save_desc_40;
 	put_cpu();
 	apm_restore_cpus(cpus);
@@ -639,12 +657,11 @@ 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;
+	apm_irq_save(flags);
 	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_irq_restore(flags);
 	gdt[0x40 / 8] = save_desc_40;
 	put_cpu();
 	apm_restore_cpus(cpus);