This patch adds the necessary Xen specific code to allow Xen to
support the CPU halting and kicking operations needed by the queue
spinlock PV code.
Signed-off-by: Waiman Long waiman.l...@hp.com
---
arch/x86/xen/spinlock.c | 63 ---
kernel/Kconfig.locks|2 +-
2 files changed, 60 insertions(+), 5 deletions(-)
diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
index 956374c..728b45b 100644
--- a/arch/x86/xen/spinlock.c
+++ b/arch/x86/xen/spinlock.c
@@ -17,6 +17,55 @@
#include xen-ops.h
#include debugfs.h
+static DEFINE_PER_CPU(int, lock_kicker_irq) = -1;
+static DEFINE_PER_CPU(char *, irq_name);
+static bool xen_pvspin = true;
+
+#ifdef CONFIG_QUEUE_SPINLOCK
+
+#include asm/qspinlock.h
+
+static void xen_qlock_kick(int cpu)
+{
+ xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR);
+}
+
+/*
+ * Halt the current CPU release it back to the host
+ */
+static void xen_qlock_wait(u8 *byte, u8 val)
+{
+ int irq = __this_cpu_read(lock_kicker_irq);
+
+ /* If kicker interrupts not initialized yet, just spin */
+ if (irq == -1)
+ return;
+
+ /* clear pending */
+ xen_clear_irq_pending(irq);
+
+ /*
+* We check the byte value after clearing pending IRQ to make sure
+* that we won't miss a wakeup event because of the clearing.
+*
+* The sync_clear_bit() call in xen_clear_irq_pending() is atomic.
+* So it is effectively a memory barrier for x86.
+*/
+ if (READ_ONCE(*byte) != val)
+ return;
+
+ /*
+* If an interrupt happens here, it will leave the wakeup irq
+* pending, which will cause xen_poll_irq() to return
+* immediately.
+*/
+
+ /* Block until irq becomes pending (or perhaps a spurious wakeup) */
+ xen_poll_irq(irq);
+}
+
+#else /* CONFIG_QUEUE_SPINLOCK */
+
enum xen_contention_stat {
TAKEN_SLOW,
TAKEN_SLOW_PICKUP,
@@ -100,12 +149,9 @@ struct xen_lock_waiting {
__ticket_t want;
};
-static DEFINE_PER_CPU(int, lock_kicker_irq) = -1;
-static DEFINE_PER_CPU(char *, irq_name);
static DEFINE_PER_CPU(struct xen_lock_waiting, lock_waiting);
static cpumask_t waiting_cpus;
-static bool xen_pvspin = true;
__visible void xen_lock_spinning(struct arch_spinlock *lock, __ticket_t want)
{
int irq = __this_cpu_read(lock_kicker_irq);
@@ -217,6 +263,7 @@ static void xen_unlock_kick(struct arch_spinlock *lock,
__ticket_t next)
}
}
}
+#endif /* CONFIG_QUEUE_SPINLOCK */
static irqreturn_t dummy_handler(int irq, void *dev_id)
{
@@ -280,8 +327,16 @@ void __init xen_init_spinlocks(void)
return;
}
printk(KERN_DEBUG xen: PV spinlocks enabled\n);
+#ifdef CONFIG_QUEUE_SPINLOCK
+ __pv_init_lock_hash();
+ pv_lock_ops.queue_spin_lock_slowpath = __pv_queue_spin_lock_slowpath;
+ pv_lock_ops.queue_spin_unlock = PV_CALLEE_SAVE(__pv_queue_spin_unlock);
+ pv_lock_ops.wait = xen_qlock_wait;
+ pv_lock_ops.kick = xen_qlock_kick;
+#else
pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(xen_lock_spinning);
pv_lock_ops.unlock_kick = xen_unlock_kick;
+#endif
}
/*
@@ -310,7 +365,7 @@ static __init int xen_parse_nopvspin(char *arg)
}
early_param(xen_nopvspin, xen_parse_nopvspin);
-#ifdef CONFIG_XEN_DEBUG_FS
+#if defined(CONFIG_XEN_DEBUG_FS) !defined(CONFIG_QUEUE_SPINLOCK)
static struct dentry *d_spin_debug;
diff --git a/kernel/Kconfig.locks b/kernel/Kconfig.locks
index 537b13e..0b42933 100644
--- a/kernel/Kconfig.locks
+++ b/kernel/Kconfig.locks
@@ -240,7 +240,7 @@ config ARCH_USE_QUEUE_SPINLOCK
config QUEUE_SPINLOCK
def_bool y if ARCH_USE_QUEUE_SPINLOCK
- depends on SMP (!PARAVIRT_SPINLOCKS || !XEN)
+ depends on SMP
config ARCH_USE_QUEUE_RWLOCK
bool
--
1.7.1
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