* Split spinlock implementation out into its own file, so it can be
* compiled in a FTRACE-compatible way.
*/
-#include <linux/kernel_stat.h>
+#include <linux/kernel.h>
#include <linux/spinlock.h>
-#include <linux/debugfs.h>
-#include <linux/log2.h>
-#include <linux/gfp.h>
#include <linux/slab.h>
+#include <linux/atomic.h>
#include <asm/paravirt.h>
#include <asm/qspinlock.h>
-#include <xen/interface/xen.h>
#include <xen/events.h>
#include "xen-ops.h"
-#include "debugfs.h"
static DEFINE_PER_CPU(int, lock_kicker_irq) = -1;
static DEFINE_PER_CPU(char *, irq_name);
+static DEFINE_PER_CPU(atomic_t, xen_qlock_wait_nest);
static bool xen_pvspin = true;
static void xen_qlock_kick(int cpu)
static void xen_qlock_wait(u8 *byte, u8 val)
{
int irq = __this_cpu_read(lock_kicker_irq);
+ atomic_t *nest_cnt = this_cpu_ptr(&xen_qlock_wait_nest);
/* If kicker interrupts not initialized yet, just spin */
- if (irq == -1)
+ if (irq == -1 || in_nmi())
return;
- /* clear pending */
- xen_clear_irq_pending(irq);
- barrier();
-
- /*
- * 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;
+ /* Detect reentry. */
+ atomic_inc(nest_cnt);
- /*
- * If an interrupt happens here, it will leave the wakeup irq
- * pending, which will cause xen_poll_irq() to return
- * immediately.
- */
+ /* If irq pending already and no nested call clear it. */
+ if (atomic_read(nest_cnt) == 1 && xen_test_irq_pending(irq)) {
+ xen_clear_irq_pending(irq);
+ } else if (READ_ONCE(*byte) == val) {
+ /* Block until irq becomes pending (or a spurious wakeup) */
+ xen_poll_irq(irq);
+ }
- /* Block until irq becomes pending (or perhaps a spurious wakeup) */
- xen_poll_irq(irq);
+ atomic_dec(nest_cnt);
}
static irqreturn_t dummy_handler(int irq, void *dev_id)
printk(KERN_DEBUG "xen: PV spinlocks enabled\n");
__pv_init_lock_hash();
- pv_lock_ops.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
- pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock);
- pv_lock_ops.wait = xen_qlock_wait;
- pv_lock_ops.kick = xen_qlock_kick;
- pv_lock_ops.vcpu_is_preempted = PV_CALLEE_SAVE(xen_vcpu_stolen);
+ pv_ops.lock.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
+ pv_ops.lock.queued_spin_unlock =
+ PV_CALLEE_SAVE(__pv_queued_spin_unlock);
+ pv_ops.lock.wait = xen_qlock_wait;
+ pv_ops.lock.kick = xen_qlock_kick;
+ pv_ops.lock.vcpu_is_preempted = PV_CALLEE_SAVE(xen_vcpu_stolen);
}
static __init int xen_parse_nopvspin(char *arg)