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authorThomas Gleixner <tglx@linutronix.de>2011-05-14 14:06:36 +0400
committerThomas Gleixner <tglx@linutronix.de>2011-05-14 14:06:36 +0400
commita18f22a968de17b29f2310cdb7ba69163e65ec15 (patch)
treea7d56d88fad5e444d7661484109758a2f436129e /arch/x86/lib/cmpxchg16b_emu.S
parenta1c57e0fec53defe745e64417eacdbd3618c3e66 (diff)
parent798778b8653f64b7b2162ac70eca10367cff6ce8 (diff)
downloadlinux-a18f22a968de17b29f2310cdb7ba69163e65ec15.tar.xz
Merge branch 'consolidate-clksrc-i8253' of master.kernel.org:~rmk/linux-2.6-arm into timers/clocksource
Conflicts: arch/ia64/kernel/cyclone.c arch/mips/kernel/i8253.c arch/x86/kernel/i8253.c Reason: Resolve conflicts so further cleanups do not conflict further Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/lib/cmpxchg16b_emu.S')
-rw-r--r--arch/x86/lib/cmpxchg16b_emu.S65
1 files changed, 65 insertions, 0 deletions
diff --git a/arch/x86/lib/cmpxchg16b_emu.S b/arch/x86/lib/cmpxchg16b_emu.S
new file mode 100644
index 000000000000..1e572c507d06
--- /dev/null
+++ b/arch/x86/lib/cmpxchg16b_emu.S
@@ -0,0 +1,65 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; version 2
+ * of the License.
+ *
+ */
+#include <linux/linkage.h>
+#include <asm/alternative-asm.h>
+#include <asm/frame.h>
+#include <asm/dwarf2.h>
+
+#ifdef CONFIG_SMP
+#define SEG_PREFIX %gs:
+#else
+#define SEG_PREFIX
+#endif
+
+.text
+
+/*
+ * Inputs:
+ * %rsi : memory location to compare
+ * %rax : low 64 bits of old value
+ * %rdx : high 64 bits of old value
+ * %rbx : low 64 bits of new value
+ * %rcx : high 64 bits of new value
+ * %al : Operation successful
+ */
+ENTRY(this_cpu_cmpxchg16b_emu)
+CFI_STARTPROC
+
+#
+# Emulate 'cmpxchg16b %gs:(%rsi)' except we return the result in %al not
+# via the ZF. Caller will access %al to get result.
+#
+# Note that this is only useful for a cpuops operation. Meaning that we
+# do *not* have a fully atomic operation but just an operation that is
+# *atomic* on a single cpu (as provided by the this_cpu_xx class of
+# macros).
+#
+this_cpu_cmpxchg16b_emu:
+ pushf
+ cli
+
+ cmpq SEG_PREFIX(%rsi), %rax
+ jne not_same
+ cmpq SEG_PREFIX 8(%rsi), %rdx
+ jne not_same
+
+ movq %rbx, SEG_PREFIX(%rsi)
+ movq %rcx, SEG_PREFIX 8(%rsi)
+
+ popf
+ mov $1, %al
+ ret
+
+ not_same:
+ popf
+ xor %al,%al
+ ret
+
+CFI_ENDPROC
+
+ENDPROC(this_cpu_cmpxchg16b_emu)