Messages in this thread Patch in this message | | | From | Denys Vlasenko <> | Subject | [PATCH 5/9] x86/asm/entry/64: simplify looping around preempt_schedule_irq | Date | Tue, 31 Mar 2015 19:00:07 +0200 |
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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 <dvlasenk@redhat.com> CC: Linus Torvalds <torvalds@linux-foundation.org> CC: Steven Rostedt <rostedt@goodmis.org> CC: Ingo Molnar <mingo@kernel.org> CC: Borislav Petkov <bp@alien8.de> CC: "H. Peter Anvin" <hpa@zytor.com> CC: Andy Lutomirski <luto@amacapital.net> CC: Oleg Nesterov <oleg@redhat.com> CC: Frederic Weisbecker <fweisbec@gmail.com> CC: Alexei Starovoitov <ast@plumgrid.com> CC: Will Drewry <wad@chromium.org> CC: Kees Cook <keescook@chromium.org> CC: x86@kernel.org CC: linux-kernel@vger.kernel.org --- 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
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