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locking/pvqspinlock, x86: Enable PV qspinlock for Xen

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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: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Daniel J Blueman <daniel@numascale.com>
Cc: Douglas Hatch <doug.hatch@hp.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paolo Bonzini <paolo.bonzini@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1429901803-29771-12-git-send-email-Waiman.Long@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
David Vrabel 2015-04-24 14:56:40 -04:00 committed by Ingo Molnar
parent bf0c7c34ad
commit e95e6f176c
2 changed files with 61 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

64
arch/x86/xen/spinlock.c
View File

@ -17,6 +17,56 @@
#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_QUEUED_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);
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;
/*
* 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_QUEUED_SPINLOCK */
enum xen_contention_stat {
TAKEN_SLOW,
TAKEN_SLOW_PICKUP,
@ -100,12 +150,9 @@ 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 +264,7 @@ static void xen_unlock_kick(struct arch_spinlock *lock, __ticket_t next)
}
}
}
#endif /* CONFIG_QUEUED_SPINLOCK */
static irqreturn_t dummy_handler(int irq, void *dev_id)
{
@ -280,8 +328,16 @@ void __init xen_init_spinlocks(void)
return;
}
printk(KERN_DEBUG "xen: PV spinlocks enabled\n");
#ifdef CONFIG_QUEUED_SPINLOCK
__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;
#else
pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(xen_lock_spinning);
pv_lock_ops.unlock_kick = xen_unlock_kick;
#endif
}
/*
@ -310,7 +366,7 @@ 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_QUEUED_SPINLOCK)
static struct dentry *d_spin_debug;

2
kernel/Kconfig.locks
View File

@ -240,7 +240,7 @@ config ARCH_USE_QUEUED_SPINLOCK
config QUEUED_SPINLOCK
def_bool y if ARCH_USE_QUEUED_SPINLOCK
depends on SMP && (!PARAVIRT_SPINLOCKS || !XEN)
depends on SMP
config ARCH_USE_QUEUE_RWLOCK
bool