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Subject[PATCH] x86: add unlikely() to fatal signal check
Ingo suggested SIGKILL check should be moved into slowpath function.
It may reduce page fault fastpath impact. This patch do that.

Suggested-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
---
arch/x86/mm/fault.c | 35 ++++++++++++++++++++---------------
1 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index f7a2a05..2dbf6bf 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -823,16 +823,30 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
force_sig_info_fault(SIGBUS, code, address, tsk, fault);
}

-static noinline void
+static noinline int
mm_fault_error(struct pt_regs *regs, unsigned long error_code,
unsigned long address, unsigned int fault)
{
+ /*
+ * Pagefault was interrupted by SIGKILL. We have no reason to
+ * continue pagefault.
+ */
+ if (fatal_signal_pending(current)) {
+ if (!(fault & VM_FAULT_RETRY))
+ up_read(&current->mm->mmap_sem);
+ if (!(error_code & PF_USER))
+ no_context(regs, error_code, address);
+ return 1;
+ }
+ if (!(fault & VM_FAULT_ERROR))
+ return 0;
+
if (fault & VM_FAULT_OOM) {
/* Kernel mode? Handle exceptions or die: */
if (!(error_code & PF_USER)) {
up_read(&current->mm->mmap_sem);
no_context(regs, error_code, address);
- return;
+ return 1;
}

out_of_memory(regs, error_code, address);
@@ -843,6 +857,7 @@ mm_fault_error(struct pt_regs *regs, unsigned long error_code,
else
BUG();
}
+ return 1;
}

static int spurious_fault_check(unsigned long error_code, pte_t *pte)
@@ -1133,19 +1148,9 @@ good_area:
*/
fault = handle_mm_fault(mm, vma, address, flags);

- if (unlikely(fault & VM_FAULT_ERROR)) {
- mm_fault_error(regs, error_code, address, fault);
- return;
- }
-
- /*
- * Pagefault was interrupted by SIGKILL. We have no reason to
- * continue pagefault.
- */
- if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) {
- if (!(error_code & PF_USER))
- no_context(regs, error_code, address);
- return;
+ if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
+ if (mm_fault_error(regs, error_code, address, fault))
+ return;
}

/*
--
1.7.3.1



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