Messages in this thread Patch in this message | | | Date | Thu, 2 Apr 2015 05:26:12 -0700 | From | tip-bot for Denys Vlasenko <> | Subject | [tip:x86/asm] x86/asm/entry/64: Simplify looping around preempt_schedule_irq() |
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Commit-ID: 36acef2510853e2831047ca9e22d333ba7a1047b Gitweb: http://git.kernel.org/tip/36acef2510853e2831047ca9e22d333ba7a1047b Author: Denys Vlasenko <dvlasenk@redhat.com> AuthorDate: Tue, 31 Mar 2015 19:00:07 +0200 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Wed, 1 Apr 2015 13:17:39 +0200
x86/asm/entry/64: Simplify looping around preempt_schedule_irq()
At the 'exit_intr' label we test whether interrupt/exception was in kernel. If it did, we jump to the 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 the test succeeded last time, preemption doesn't change the fact that interrupt/exception was in the kernel.
We can go back directly to checking PER_CPU_VAR(__preempt_count) instead.
This makes the 'exit_intr' label unused, drop it.
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Cc: Alexei Starovoitov <ast@plumgrid.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Will Drewry <wad@chromium.org> Link: http://lkml.kernel.org/r/1427821211-25099-5-git-send-email-dvlasenk@redhat.com Signed-off-by: Ingo Molnar <mingo@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 /*
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