From 1e696f638b523958ee3d95e655becdb4c4b6fcde Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Wed, 20 Aug 2008 17:02:20 -0700 Subject: [PATCH] xen: allow interrupts to be enabled while doing a blocking spin If spin_lock is called in an interrupts-enabled context, we can safely enable interrupts while spinning. We don't bother for the actual spin loop, but if we timeout and fall back to blocking, it's definitely worthwhile enabling interrupts if possible. Signed-off-by: Jeremy Fitzhardinge Acked-by: Jan Beulich Signed-off-by: Ingo Molnar --- arch/x86/xen/spinlock.c | 30 +++++++++++++++++++++++++++--- 1 file changed, 27 insertions(+), 3 deletions(-) diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c index 0d8f3b2d9be..e6061f2e64f 100644 --- a/arch/x86/xen/spinlock.c +++ b/arch/x86/xen/spinlock.c @@ -23,6 +23,7 @@ static struct xen_spinlock_stats u32 taken_slow_nested; u32 taken_slow_pickup; u32 taken_slow_spurious; + u32 taken_slow_irqenable; u64 released; u32 released_slow; @@ -167,12 +168,13 @@ static inline void unspinning_lock(struct xen_spinlock *xl, struct xen_spinlock __get_cpu_var(lock_spinners) = prev; } -static noinline int xen_spin_lock_slow(struct raw_spinlock *lock) +static noinline int xen_spin_lock_slow(struct raw_spinlock *lock, bool irq_enable) { struct xen_spinlock *xl = (struct xen_spinlock *)lock; struct xen_spinlock *prev; int irq = __get_cpu_var(lock_kicker_irq); int ret; + unsigned long flags; /* If kicker interrupts not initialized yet, just spin */ if (irq == -1) @@ -181,6 +183,12 @@ static noinline int xen_spin_lock_slow(struct raw_spinlock *lock) /* announce we're spinning */ prev = spinning_lock(xl); + flags = __raw_local_save_flags(); + if (irq_enable) { + ADD_STATS(taken_slow_irqenable, 1); + raw_local_irq_enable(); + } + ADD_STATS(taken_slow, 1); ADD_STATS(taken_slow_nested, prev != NULL); @@ -220,11 +228,12 @@ static noinline int xen_spin_lock_slow(struct raw_spinlock *lock) kstat_this_cpu.irqs[irq]++; out: + raw_local_irq_restore(flags); unspinning_lock(xl, prev); return ret; } -static void xen_spin_lock(struct raw_spinlock *lock) +static inline void __xen_spin_lock(struct raw_spinlock *lock, bool irq_enable) { struct xen_spinlock *xl = (struct xen_spinlock *)lock; unsigned timeout; @@ -254,11 +263,23 @@ static void xen_spin_lock(struct raw_spinlock *lock) : "memory"); spin_time_accum_fast(start_spin_fast); - } while (unlikely(oldval != 0 && (TIMEOUT == ~0 || !xen_spin_lock_slow(lock)))); + + } while (unlikely(oldval != 0 && + (TIMEOUT == ~0 || !xen_spin_lock_slow(lock, irq_enable)))); spin_time_accum(start_spin); } +static void xen_spin_lock(struct raw_spinlock *lock) +{ + __xen_spin_lock(lock, false); +} + +static void xen_spin_lock_flags(struct raw_spinlock *lock, unsigned long flags) +{ + __xen_spin_lock(lock, !raw_irqs_disabled_flags(flags)); +} + static noinline void xen_spin_unlock_slow(struct xen_spinlock *xl) { int cpu; @@ -323,6 +344,7 @@ void __init xen_init_spinlocks(void) pv_lock_ops.spin_is_locked = xen_spin_is_locked; pv_lock_ops.spin_is_contended = xen_spin_is_contended; pv_lock_ops.spin_lock = xen_spin_lock; + pv_lock_ops.spin_lock_flags = xen_spin_lock_flags; pv_lock_ops.spin_trylock = xen_spin_trylock; pv_lock_ops.spin_unlock = xen_spin_unlock; } @@ -353,6 +375,8 @@ static int __init xen_spinlock_debugfs(void) &spinlock_stats.taken_slow_pickup); debugfs_create_u32("taken_slow_spurious", 0444, d_spin_debug, &spinlock_stats.taken_slow_spurious); + debugfs_create_u32("taken_slow_irqenable", 0444, d_spin_debug, + &spinlock_stats.taken_slow_irqenable); debugfs_create_u64("released", 0444, d_spin_debug, &spinlock_stats.released); debugfs_create_u32("released_slow", 0444, d_spin_debug, -- 2.41.0