diff options
Diffstat (limited to 'arch/x86/xen/spinlock.c')
| -rw-r--r-- | arch/x86/xen/spinlock.c | 35 |
1 files changed, 14 insertions, 21 deletions
diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c index f42e78de1e10..85872a08994a 100644 --- a/arch/x86/xen/spinlock.c +++ b/arch/x86/xen/spinlock.c @@ -8,6 +8,7 @@ #include <linux/log2.h> #include <linux/gfp.h> #include <linux/slab.h> +#include <linux/atomic.h> #include <asm/paravirt.h> @@ -19,6 +20,7 @@ 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; #ifdef CONFIG_QUEUED_SPINLOCKS @@ -42,33 +44,24 @@ 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); } #else /* CONFIG_QUEUED_SPINLOCKS */ |