At this label, we test whether interrupt/exception was in kernel. If it did, we jump to preemption check. If preemption does happen (IOW if we call preempt_schedule_irq), we go back to exit_intr.
But it's pointless, we already know that test succeeded last time, preemption doesn't change the fact that interrupt/exception was in kernel. We can go back directly to checking PER_CPU_VAR(__preempt_count) instead. This makes exit_intr label unused. Dropping it. While at it, tidy up TEST insn width to use shorter insn form, use logically correct JZ mnemonic instead of JE (this doesn't change code), use X86_EFLAGS_IF_BIT instead of literal 9. Signed-off-by: Denys Vlasenko <[email protected]> CC: Linus Torvalds <[email protected]> CC: Steven Rostedt <[email protected]> CC: Ingo Molnar <[email protected]> CC: Borislav Petkov <[email protected]> CC: "H. Peter Anvin" <[email protected]> CC: Andy Lutomirski <[email protected]> CC: Oleg Nesterov <[email protected]> CC: Frederic Weisbecker <[email protected]> CC: Alexei Starovoitov <[email protected]> CC: Will Drewry <[email protected]> CC: Kees Cook <[email protected]> CC: [email protected] CC: [email protected] --- arch/x86/kernel/entry_64.S | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 16bf357..bc90f63 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -653,9 +653,8 @@ ret_from_intr: CFI_DEF_CFA_REGISTER rsp CFI_ADJUST_CFA_OFFSET RBP -exit_intr: - testl $3,CS(%rsp) - je retint_kernel + testb $3,CS(%rsp) + jz retint_kernel /* Interrupt came from user space */ GET_THREAD_INFO(%rcx) @@ -740,12 +739,12 @@ retint_kernel: #ifdef CONFIG_PREEMPT /* Interrupts are off */ /* Check if we need preemption */ - cmpl $0,PER_CPU_VAR(__preempt_count) - jnz 1f - bt $9,EFLAGS(%rsp) /* interrupts were off? */ + bt $X86_EFLAGS_IF_BIT,EFLAGS(%rsp) /* interrupts were off? */ jnc 1f +0: cmpl $0,PER_CPU_VAR(__preempt_count) + jnz 1f call preempt_schedule_irq - jmp exit_intr + jmp 0b 1: #endif /* -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
