From 42c059e04d507802006911e316d86aa8ef75eb73 Mon Sep 17 00:00:00 2001 From: Chuck Ebbert <76306.1226@compuserve.com> Date: Thu, 23 Mar 2006 02:59:55 -0800 Subject: [PATCH] i386 spinlocks: disable interrupts only if we enabled them _raw_spin_lock_flags() is entered with interrupts disabled. If it cannot obtain a spinlock, it checks the flags that were passed and re-enables interrupts before spinning if that's how the flags are set. When the spinlock might be available, it disables interrupts (even if they are already disabled) before trying to get the lock. Change that so interrupts are only disabled if they have been enabled. This costs nine bytes of duplicated spinloop code. Fastpath before patch: jle not-taken conditional jump cli disable interrupts jmp unconditional jump Fastpath after patch, if interrupts were not enabled: jg taken conditional branch Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com> Acked-by: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-i386/spinlock.h | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) (limited to 'include/asm-i386') diff --git a/include/asm-i386/spinlock.h b/include/asm-i386/spinlock.h index a1b8a8a30e2..d76b7693cf1 100644 --- a/include/asm-i386/spinlock.h +++ b/include/asm-i386/spinlock.h @@ -35,18 +35,23 @@ #define __raw_spin_lock_string_flags \ "\n1:\t" \ "lock ; decb %0\n\t" \ - "jns 4f\n\t" \ + "jns 5f\n" \ "2:\t" \ "testl $0x200, %1\n\t" \ - "jz 3f\n\t" \ - "sti\n\t" \ + "jz 4f\n\t" \ + "sti\n" \ "3:\t" \ "rep;nop\n\t" \ "cmpb $0, %0\n\t" \ "jle 3b\n\t" \ "cli\n\t" \ "jmp 1b\n" \ - "4:\n\t" + "4:\t" \ + "rep;nop\n\t" \ + "cmpb $0, %0\n\t" \ + "jg 1b\n\t" \ + "jmp 4b\n" \ + "5:\n\t" #define __raw_spin_lock_string_up \ "\n\tdecb %0" -- cgit v1.2.3