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x86/asm/entry/64: Simplify looping around preempt_schedule_irq()

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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>
This commit is contained in:
Denys Vlasenko 2015-03-31 19:00:07 +02:00 committed by Ingo Molnar
parent 32a04077fe
commit 36acef2510
1 changed files with 3 additions and 4 deletions
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7
arch/x86/kernel/entry_64.S
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@ -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
/*