2 * Split spinlock implementation out into its own file, so it can be
3 * compiled in a FTRACE-compatible way.
5 #include <linux/kernel_stat.h>
6 #include <linux/spinlock.h>
7 #include <linux/debugfs.h>
8 #include <linux/log2.h>
10 #include <linux/slab.h>
12 #include <asm/paravirt.h>
14 #include <xen/interface/xen.h>
15 #include <xen/events.h>
20 static DEFINE_PER_CPU(int, lock_kicker_irq
) = -1;
21 static DEFINE_PER_CPU(char *, irq_name
);
22 static bool xen_pvspin
= true;
24 #include <asm/qspinlock.h>
26 static void xen_qlock_kick(int cpu
)
28 int irq
= per_cpu(lock_kicker_irq
, cpu
);
30 /* Don't kick if the target's kicker interrupt is not initialized. */
34 xen_send_IPI_one(cpu
, XEN_SPIN_UNLOCK_VECTOR
);
38 * Halt the current CPU & release it back to the host
40 static void xen_qlock_wait(u8
*byte
, u8 val
)
42 int irq
= __this_cpu_read(lock_kicker_irq
);
44 /* If kicker interrupts not initialized yet, just spin */
49 xen_clear_irq_pending(irq
);
53 * We check the byte value after clearing pending IRQ to make sure
54 * that we won't miss a wakeup event because of the clearing.
56 * The sync_clear_bit() call in xen_clear_irq_pending() is atomic.
57 * So it is effectively a memory barrier for x86.
59 if (READ_ONCE(*byte
) != val
)
63 * If an interrupt happens here, it will leave the wakeup irq
64 * pending, which will cause xen_poll_irq() to return
68 /* Block until irq becomes pending (or perhaps a spurious wakeup) */
72 static irqreturn_t
dummy_handler(int irq
, void *dev_id
)
78 void xen_init_lock_cpu(int cpu
)
86 WARN(per_cpu(lock_kicker_irq
, cpu
) >= 0, "spinlock on CPU%d exists on IRQ%d!\n",
87 cpu
, per_cpu(lock_kicker_irq
, cpu
));
89 name
= kasprintf(GFP_KERNEL
, "spinlock%d", cpu
);
90 irq
= bind_ipi_to_irqhandler(XEN_SPIN_UNLOCK_VECTOR
,
93 IRQF_PERCPU
|IRQF_NOBALANCING
,
98 disable_irq(irq
); /* make sure it's never delivered */
99 per_cpu(lock_kicker_irq
, cpu
) = irq
;
100 per_cpu(irq_name
, cpu
) = name
;
103 printk("cpu %d spinlock event irq %d\n", cpu
, irq
);
106 void xen_uninit_lock_cpu(int cpu
)
111 unbind_from_irqhandler(per_cpu(lock_kicker_irq
, cpu
), NULL
);
112 per_cpu(lock_kicker_irq
, cpu
) = -1;
113 kfree(per_cpu(irq_name
, cpu
));
114 per_cpu(irq_name
, cpu
) = NULL
;
119 * Our init of PV spinlocks is split in two init functions due to us
120 * using paravirt patching and jump labels patching and having to do
121 * all of this before SMP code is invoked.
123 * The paravirt patching needs to be done _before_ the alternative asm code
124 * is started, otherwise we would not patch the core kernel code.
126 void __init
xen_init_spinlocks(void)
130 printk(KERN_DEBUG
"xen: PV spinlocks disabled\n");
133 printk(KERN_DEBUG
"xen: PV spinlocks enabled\n");
135 __pv_init_lock_hash();
136 pv_lock_ops
.queued_spin_lock_slowpath
= __pv_queued_spin_lock_slowpath
;
137 pv_lock_ops
.queued_spin_unlock
= PV_CALLEE_SAVE(__pv_queued_spin_unlock
);
138 pv_lock_ops
.wait
= xen_qlock_wait
;
139 pv_lock_ops
.kick
= xen_qlock_kick
;
143 * While the jump_label init code needs to happend _after_ the jump labels are
144 * enabled and before SMP is started. Hence we use pre-SMP initcall level
145 * init. We cannot do it in xen_init_spinlocks as that is done before
146 * jump labels are activated.
148 static __init
int xen_init_spinlocks_jump(void)
156 static_key_slow_inc(¶virt_ticketlocks_enabled
);
159 early_initcall(xen_init_spinlocks_jump
);
161 static __init
int xen_parse_nopvspin(char *arg
)
166 early_param("xen_nopvspin", xen_parse_nopvspin
);