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>

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 7b23431..7040d7e 100644 (file)
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -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