At exit_intr 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. 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 | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 9f8d01f..bad285d 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -654,7 +654,6 @@ ret_from_intr: CFI_DEF_CFA_REGISTER rsp CFI_ADJUST_CFA_OFFSET RBP -exit_intr: testl $3,CS(%rsp) je retint_kernel /* Interrupt came from user space */ @@ -741,12 +740,12 @@ 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? */ 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/
