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-rw-r--r--arch/x86/include/asm/qspinlock_paravirt.h59
1 files changed, 59 insertions, 0 deletions
diff --git a/arch/x86/include/asm/qspinlock_paravirt.h b/arch/x86/include/asm/qspinlock_paravirt.h
index b002e711ba88..9f92c180ed2f 100644
--- a/arch/x86/include/asm/qspinlock_paravirt.h
+++ b/arch/x86/include/asm/qspinlock_paravirt.h
@@ -1,6 +1,65 @@
#ifndef __ASM_QSPINLOCK_PARAVIRT_H
#define __ASM_QSPINLOCK_PARAVIRT_H
+/*
+ * For x86-64, PV_CALLEE_SAVE_REGS_THUNK() saves and restores 8 64-bit
+ * registers. For i386, however, only 1 32-bit register needs to be saved
+ * and restored. So an optimized version of __pv_queued_spin_unlock() is
+ * hand-coded for 64-bit, but it isn't worthwhile to do it for 32-bit.
+ */
+#ifdef CONFIG_64BIT
+
+PV_CALLEE_SAVE_REGS_THUNK(__pv_queued_spin_unlock_slowpath);
+#define __pv_queued_spin_unlock __pv_queued_spin_unlock
+#define PV_UNLOCK "__raw_callee_save___pv_queued_spin_unlock"
+#define PV_UNLOCK_SLOWPATH "__raw_callee_save___pv_queued_spin_unlock_slowpath"
+
+/*
+ * Optimized assembly version of __raw_callee_save___pv_queued_spin_unlock
+ * which combines the registers saving trunk and the body of the following
+ * C code:
+ *
+ * void __pv_queued_spin_unlock(struct qspinlock *lock)
+ * {
+ * struct __qspinlock *l = (void *)lock;
+ * u8 lockval = cmpxchg(&l->locked, _Q_LOCKED_VAL, 0);
+ *
+ * if (likely(lockval == _Q_LOCKED_VAL))
+ * return;
+ * pv_queued_spin_unlock_slowpath(lock, lockval);
+ * }
+ *
+ * For x86-64,
+ * rdi = lock (first argument)
+ * rsi = lockval (second argument)
+ * rdx = internal variable (set to 0)
+ */
+asm (".pushsection .text;"
+ ".globl " PV_UNLOCK ";"
+ ".align 4,0x90;"
+ PV_UNLOCK ": "
+ "push %rdx;"
+ "mov $0x1,%eax;"
+ "xor %edx,%edx;"
+ "lock cmpxchg %dl,(%rdi);"
+ "cmp $0x1,%al;"
+ "jne .slowpath;"
+ "pop %rdx;"
+ "ret;"
+ ".slowpath: "
+ "push %rsi;"
+ "movzbl %al,%esi;"
+ "call " PV_UNLOCK_SLOWPATH ";"
+ "pop %rsi;"
+ "pop %rdx;"
+ "ret;"
+ ".size " PV_UNLOCK ", .-" PV_UNLOCK ";"
+ ".popsection");
+
+#else /* CONFIG_64BIT */
+
+extern void __pv_queued_spin_unlock(struct qspinlock *lock);
PV_CALLEE_SAVE_REGS_THUNK(__pv_queued_spin_unlock);
+#endif /* CONFIG_64BIT */
#endif