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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: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Josh 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2019-05-07 23:25:54 +02:00 committed by Ingo Molnar
parent c21ac93288
commit 5e1246ff2d
1 changed files with 10 additions and 14 deletions
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24
arch/x86/entry/entry_32.S
View File

@ -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