The code flow around the return from interrupt preemption point seems needlesly 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 --- arch/x86/entry/entry_32.S | 24 ++++++++++-------------- 1 file changed, 10 insertions(+), 14 deletions(-)
--- 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 @@ END(ret_from_fork) 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 @@ ENTRY(entry_INT80_32) 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