 e08fbb78f0
			
		
	
	
	e08fbb78f0
	
	
	
		
			
			I triggered a triple fault with gcc 4.5.1 because it did not honor the inline annotation to arch_local_save_flags() function and that function was added to the pool of functions traced by the function tracer. When preempt_schedule() called arch_local_save_flags() (called by irqs_disabled()), it was traced, but the first thing the function tracer does is disable preemption. When it enables preemption, the NEED_RESCHED flag will not have been cleared and the preemption check will trigger the call to preempt_schedule() again. Although the dynamic function tracer crashed immediately, the static version of the function tracer (CONFIG_DYNAMIC_FTRACE is not set) actually was able to show where the problem was. swapper-1 3.N.. 103885us : arch_local_save_flags <-preempt_schedule swapper-1 3.N.. 103886us : arch_local_save_flags <-preempt_schedule swapper-1 3.N.. 103886us : arch_local_save_flags <-preempt_schedule swapper-1 3.N.. 103887us : arch_local_save_flags <-preempt_schedule swapper-1 3.N.. 103887us : arch_local_save_flags <-preempt_schedule swapper-1 3.N.. 103888us : arch_local_save_flags <-preempt_schedule swapper-1 3.N.. 103888us : arch_local_save_flags <-preempt_schedule It went on for a while before it triple faulted with a corrupted stack. The arch_local_save_flags and arch_local_irq_* functions should not be traced. Even though they are marked as inline, gcc may still make them a function and enable tracing of them. The simple solution is to just mark them as notrace. I had to add the <linux/types.h> for this file to include the notrace tag. Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/20110702033852.733414762@goodmis.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
		
			
				
	
	
		
			209 lines
		
	
	
	
		
			4 KiB
			
		
	
	
	
		
			C
		
	
	
	
	
	
			
		
		
	
	
			209 lines
		
	
	
	
		
			4 KiB
			
		
	
	
	
		
			C
		
	
	
	
	
	
| #ifndef _X86_IRQFLAGS_H_
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| #define _X86_IRQFLAGS_H_
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| 
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| #include <asm/processor-flags.h>
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| 
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| #ifndef __ASSEMBLY__
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| /*
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|  * Interrupt control:
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|  */
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| 
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| static inline unsigned long native_save_fl(void)
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| {
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| 	unsigned long flags;
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| 
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| 	/*
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| 	 * "=rm" is safe here, because "pop" adjusts the stack before
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| 	 * it evaluates its effective address -- this is part of the
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| 	 * documented behavior of the "pop" instruction.
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| 	 */
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| 	asm volatile("# __raw_save_flags\n\t"
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| 		     "pushf ; pop %0"
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| 		     : "=rm" (flags)
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| 		     : /* no input */
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| 		     : "memory");
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| 
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| 	return flags;
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| }
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| 
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| static inline void native_restore_fl(unsigned long flags)
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| {
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| 	asm volatile("push %0 ; popf"
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| 		     : /* no output */
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| 		     :"g" (flags)
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| 		     :"memory", "cc");
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| }
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| 
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| static inline void native_irq_disable(void)
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| {
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| 	asm volatile("cli": : :"memory");
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| }
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| 
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| static inline void native_irq_enable(void)
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| {
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| 	asm volatile("sti": : :"memory");
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| }
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| 
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| static inline void native_safe_halt(void)
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| {
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| 	asm volatile("sti; hlt": : :"memory");
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| }
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| 
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| static inline void native_halt(void)
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| {
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| 	asm volatile("hlt": : :"memory");
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| }
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| 
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| #endif
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| 
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| #ifdef CONFIG_PARAVIRT
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| #include <asm/paravirt.h>
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| #else
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| #ifndef __ASSEMBLY__
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| #include <linux/types.h>
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| 
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| static inline notrace unsigned long arch_local_save_flags(void)
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| {
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| 	return native_save_fl();
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| }
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| 
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| static inline notrace void arch_local_irq_restore(unsigned long flags)
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| {
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| 	native_restore_fl(flags);
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| }
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| 
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| static inline notrace void arch_local_irq_disable(void)
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| {
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| 	native_irq_disable();
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| }
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| 
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| static inline notrace void arch_local_irq_enable(void)
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| {
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| 	native_irq_enable();
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| }
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| 
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| /*
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|  * Used in the idle loop; sti takes one instruction cycle
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|  * to complete:
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|  */
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| static inline void arch_safe_halt(void)
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| {
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| 	native_safe_halt();
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| }
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| 
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| /*
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|  * Used when interrupts are already enabled or to
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|  * shutdown the processor:
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|  */
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| static inline void halt(void)
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| {
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| 	native_halt();
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| }
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| 
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| /*
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|  * For spinlocks, etc:
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|  */
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| static inline notrace unsigned long arch_local_irq_save(void)
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| {
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| 	unsigned long flags = arch_local_save_flags();
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| 	arch_local_irq_disable();
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| 	return flags;
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| }
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| #else
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| 
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| #define ENABLE_INTERRUPTS(x)	sti
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| #define DISABLE_INTERRUPTS(x)	cli
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| 
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| #ifdef CONFIG_X86_64
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| #define SWAPGS	swapgs
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| /*
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|  * Currently paravirt can't handle swapgs nicely when we
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|  * don't have a stack we can rely on (such as a user space
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|  * stack).  So we either find a way around these or just fault
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|  * and emulate if a guest tries to call swapgs directly.
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|  *
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|  * Either way, this is a good way to document that we don't
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|  * have a reliable stack. x86_64 only.
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|  */
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| #define SWAPGS_UNSAFE_STACK	swapgs
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| 
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| #define PARAVIRT_ADJUST_EXCEPTION_FRAME	/*  */
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| 
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| #define INTERRUPT_RETURN	iretq
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| #define USERGS_SYSRET64				\
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| 	swapgs;					\
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| 	sysretq;
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| #define USERGS_SYSRET32				\
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| 	swapgs;					\
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| 	sysretl
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| #define ENABLE_INTERRUPTS_SYSEXIT32		\
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| 	swapgs;					\
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| 	sti;					\
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| 	sysexit
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| 
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| #else
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| #define INTERRUPT_RETURN		iret
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| #define ENABLE_INTERRUPTS_SYSEXIT	sti; sysexit
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| #define GET_CR0_INTO_EAX		movl %cr0, %eax
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| #endif
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| 
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| 
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| #endif /* __ASSEMBLY__ */
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| #endif /* CONFIG_PARAVIRT */
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| 
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| #ifndef __ASSEMBLY__
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| static inline int arch_irqs_disabled_flags(unsigned long flags)
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| {
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| 	return !(flags & X86_EFLAGS_IF);
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| }
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| 
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| static inline int arch_irqs_disabled(void)
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| {
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| 	unsigned long flags = arch_local_save_flags();
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| 
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| 	return arch_irqs_disabled_flags(flags);
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| }
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| 
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| #else
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| 
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| #ifdef CONFIG_X86_64
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| #define ARCH_LOCKDEP_SYS_EXIT		call lockdep_sys_exit_thunk
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| #define ARCH_LOCKDEP_SYS_EXIT_IRQ	\
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| 	TRACE_IRQS_ON; \
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| 	sti; \
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| 	SAVE_REST; \
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| 	LOCKDEP_SYS_EXIT; \
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| 	RESTORE_REST; \
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| 	cli; \
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| 	TRACE_IRQS_OFF;
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| 
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| #else
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| #define ARCH_LOCKDEP_SYS_EXIT			\
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| 	pushl %eax;				\
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| 	pushl %ecx;				\
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| 	pushl %edx;				\
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| 	call lockdep_sys_exit;			\
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| 	popl %edx;				\
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| 	popl %ecx;				\
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| 	popl %eax;
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| 
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| #define ARCH_LOCKDEP_SYS_EXIT_IRQ
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| #endif
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| 
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| #ifdef CONFIG_TRACE_IRQFLAGS
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| #  define TRACE_IRQS_ON		call trace_hardirqs_on_thunk;
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| #  define TRACE_IRQS_OFF	call trace_hardirqs_off_thunk;
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| #else
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| #  define TRACE_IRQS_ON
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| #  define TRACE_IRQS_OFF
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| #endif
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| #ifdef CONFIG_DEBUG_LOCK_ALLOC
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| #  define LOCKDEP_SYS_EXIT	ARCH_LOCKDEP_SYS_EXIT
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| #  define LOCKDEP_SYS_EXIT_IRQ	ARCH_LOCKDEP_SYS_EXIT_IRQ
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| # else
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| #  define LOCKDEP_SYS_EXIT
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| #  define LOCKDEP_SYS_EXIT_IRQ
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| # endif
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| 
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| #endif /* __ASSEMBLY__ */
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| #endif
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