Commit 5e1246ff authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

x86/entry/32: Clean up return from interrupt preemption path 



The code flow around the return from interrupt preemption point seems
needlessly complicated.

There is only one site jumping to resume_kernel, and none (outside of
resume_kernel) jumping to restore_all_kernel. Inline resume_kernel
in restore_all_kernel and avoid the CONFIG_PREEMPT dependent label.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent c21ac932

arch/x86/entry/entry_32.S

+10 −14
Original line number Diff line number Diff line
@@ -67,7 +67,6 @@ 
# define preempt_stop(clobbers)	DISABLE_INTERRUPTS(clobbers); TRACE_IRQS_OFF

#else

# define preempt_stop(clobbers)

# define resume_kernel		restore_all_kernel

#endif



.macro TRACE_IRQS_IRET
@@ -755,7 +754,7 @@ ret_from_intr: 
	andl	$SEGMENT_RPL_MASK, %eax

#endif

	cmpl	$USER_RPL, %eax

	jb	resume_kernel			# not returning to v8086 or userspace

	jb	restore_all_kernel		# not returning to v8086 or userspace



ENTRY(resume_userspace)

	DISABLE_INTERRUPTS(CLBR_ANY)
@@ -765,18 +764,6 @@ ENTRY(resume_userspace) 
	jmp	restore_all

END(ret_from_exception)



#ifdef CONFIG_PREEMPT

ENTRY(resume_kernel)

	DISABLE_INTERRUPTS(CLBR_ANY)

	cmpl	$0, PER_CPU_VAR(__preempt_count)

	jnz	restore_all_kernel

	testl	$X86_EFLAGS_IF, PT_EFLAGS(%esp)	# interrupts off (exception path) ?

	jz	restore_all_kernel

	call	preempt_schedule_irq

	jmp	restore_all_kernel

END(resume_kernel)

#endif



GLOBAL(__begin_SYSENTER_singlestep_region)

/*

 * All code from here through __end_SYSENTER_singlestep_region is subject
@@ -1027,6 +1014,15 @@ restore_all: 
	INTERRUPT_RETURN



restore_all_kernel:

#ifdef CONFIG_PREEMPT

	DISABLE_INTERRUPTS(CLBR_ANY)

	cmpl	$0, PER_CPU_VAR(__preempt_count)

	jnz	.Lno_preempt

	testl	$X86_EFLAGS_IF, PT_EFLAGS(%esp)	# interrupts off (exception path) ?

	jz	.Lno_preempt

	call	preempt_schedule_irq

.Lno_preempt:

#endif

	TRACE_IRQS_IRET

	PARANOID_EXIT_TO_KERNEL_MODE

	BUG_IF_WRONG_CR3

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