From: David Vrabel Date: Fri, 19 Jul 2013 14:52:00 +0000 (+0100) Subject: xen/evtchn: improve scalability by using per-user locks X-Git-Tag: upstream/snapshot3+hdmi~4249^2~34 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=73cc4bb0c79eebe1f0e92b700d9fe8d1c9b061bb;p=platform%2Fadaptation%2Frenesas_rcar%2Frenesas_kernel.git xen/evtchn: improve scalability by using per-user locks The global array of port users and the port_user_lock limits scalability of the evtchn device. Instead of the global array lookup, use a per-use (per-fd) tree of event channels bound by that user and protect the tree with a per-user lock. This is also a prerequiste for extended the number of supported event channels, by removing the fixed size, per-event channel array. Signed-off-by: David Vrabel Signed-off-by: Konrad Rzeszutek Wilk --- diff --git a/drivers/xen/evtchn.c b/drivers/xen/evtchn.c index b6165e0..f328f12 100644 --- a/drivers/xen/evtchn.c +++ b/drivers/xen/evtchn.c @@ -57,6 +57,7 @@ struct per_user_data { struct mutex bind_mutex; /* serialize bind/unbind operations */ + struct rb_root evtchns; /* Notification ring, accessed via /dev/xen/evtchn. */ #define EVTCHN_RING_SIZE (PAGE_SIZE / sizeof(evtchn_port_t)) @@ -64,6 +65,7 @@ struct per_user_data { evtchn_port_t *ring; unsigned int ring_cons, ring_prod, ring_overflow; struct mutex ring_cons_mutex; /* protect against concurrent readers */ + spinlock_t ring_prod_lock; /* product against concurrent interrupts */ /* Processes wait on this queue when ring is empty. */ wait_queue_head_t evtchn_wait; @@ -71,54 +73,79 @@ struct per_user_data { const char *name; }; -/* - * Who's bound to each port? This is logically an array of struct - * per_user_data *, but we encode the current enabled-state in bit 0. - */ -static unsigned long *port_user; -static DEFINE_SPINLOCK(port_user_lock); /* protects port_user[] and ring_prod */ +struct user_evtchn { + struct rb_node node; + struct per_user_data *user; + unsigned port; + bool enabled; +}; -static inline struct per_user_data *get_port_user(unsigned port) +static int add_evtchn(struct per_user_data *u, struct user_evtchn *evtchn) { - return (struct per_user_data *)(port_user[port] & ~1); -} + struct rb_node **new = &(u->evtchns.rb_node), *parent = NULL; -static inline void set_port_user(unsigned port, struct per_user_data *u) -{ - port_user[port] = (unsigned long)u; + while (*new) { + struct user_evtchn *this; + + this = container_of(*new, struct user_evtchn, node); + + parent = *new; + if (this->port < evtchn->port) + new = &((*new)->rb_left); + else if (this->port > evtchn->port) + new = &((*new)->rb_right); + else + return -EEXIST; + } + + /* Add new node and rebalance tree. */ + rb_link_node(&evtchn->node, parent, new); + rb_insert_color(&evtchn->node, &u->evtchns); + + return 0; } -static inline bool get_port_enabled(unsigned port) +static void del_evtchn(struct per_user_data *u, struct user_evtchn *evtchn) { - return port_user[port] & 1; + rb_erase(&evtchn->node, &u->evtchns); + kfree(evtchn); } -static inline void set_port_enabled(unsigned port, bool enabled) +static struct user_evtchn *find_evtchn(struct per_user_data *u, unsigned port) { - if (enabled) - port_user[port] |= 1; - else - port_user[port] &= ~1; + struct rb_node *node = u->evtchns.rb_node; + + while (node) { + struct user_evtchn *evtchn; + + evtchn = container_of(node, struct user_evtchn, node); + + if (evtchn->port < port) + node = node->rb_left; + else if (evtchn->port > port) + node = node->rb_right; + else + return evtchn; + } + return NULL; } static irqreturn_t evtchn_interrupt(int irq, void *data) { - unsigned int port = (unsigned long)data; - struct per_user_data *u; - - spin_lock(&port_user_lock); - - u = get_port_user(port); + struct user_evtchn *evtchn = data; + struct per_user_data *u = evtchn->user; - WARN(!get_port_enabled(port), + WARN(!evtchn->enabled, "Interrupt for port %d, but apparently not enabled; per-user %p\n", - port, u); + evtchn->port, u); disable_irq_nosync(irq); - set_port_enabled(port, false); + evtchn->enabled = false; + + spin_lock(&u->ring_prod_lock); if ((u->ring_prod - u->ring_cons) < EVTCHN_RING_SIZE) { - u->ring[EVTCHN_RING_MASK(u->ring_prod)] = port; + u->ring[EVTCHN_RING_MASK(u->ring_prod)] = evtchn->port; wmb(); /* Ensure ring contents visible */ if (u->ring_cons == u->ring_prod++) { wake_up_interruptible(&u->evtchn_wait); @@ -128,7 +155,7 @@ static irqreturn_t evtchn_interrupt(int irq, void *data) } else u->ring_overflow = 1; - spin_unlock(&port_user_lock); + spin_unlock(&u->ring_prod_lock); return IRQ_HANDLED; } @@ -229,20 +256,20 @@ static ssize_t evtchn_write(struct file *file, const char __user *buf, if (copy_from_user(kbuf, buf, count) != 0) goto out; - spin_lock_irq(&port_user_lock); + mutex_lock(&u->bind_mutex); for (i = 0; i < (count/sizeof(evtchn_port_t)); i++) { unsigned port = kbuf[i]; + struct user_evtchn *evtchn; - if (port < NR_EVENT_CHANNELS && - get_port_user(port) == u && - !get_port_enabled(port)) { - set_port_enabled(port, true); + evtchn = find_evtchn(u, port); + if (evtchn && !evtchn->enabled) { + evtchn->enabled = true; enable_irq(irq_from_evtchn(port)); } } - spin_unlock_irq(&port_user_lock); + mutex_unlock(&u->bind_mutex); rc = count; @@ -253,6 +280,8 @@ static ssize_t evtchn_write(struct file *file, const char __user *buf, static int evtchn_bind_to_user(struct per_user_data *u, int port) { + struct user_evtchn *evtchn; + struct evtchn_close close; int rc = 0; /* @@ -263,35 +292,47 @@ static int evtchn_bind_to_user(struct per_user_data *u, int port) * interrupt handler yet, and our caller has already * serialized bind operations.) */ - BUG_ON(get_port_user(port) != NULL); - set_port_user(port, u); - set_port_enabled(port, true); /* start enabled */ + + evtchn = kzalloc(sizeof(*evtchn), GFP_KERNEL); + if (!evtchn) + return -ENOMEM; + + evtchn->user = u; + evtchn->port = port; + evtchn->enabled = true; /* start enabled */ + + rc = add_evtchn(u, evtchn); + if (rc < 0) + goto err; rc = bind_evtchn_to_irqhandler(port, evtchn_interrupt, IRQF_DISABLED, - u->name, (void *)(unsigned long)port); - if (rc >= 0) - rc = evtchn_make_refcounted(port); - else { - /* bind failed, should close the port now */ - struct evtchn_close close; - close.port = port; - if (HYPERVISOR_event_channel_op(EVTCHNOP_close, &close) != 0) - BUG(); - set_port_user(port, NULL); - } + u->name, evtchn); + if (rc < 0) + goto err; + rc = evtchn_make_refcounted(port); + return rc; + +err: + /* bind failed, should close the port now */ + close.port = port; + if (HYPERVISOR_event_channel_op(EVTCHNOP_close, &close) != 0) + BUG(); + del_evtchn(u, evtchn); + kfree(evtchn); return rc; } -static void evtchn_unbind_from_user(struct per_user_data *u, int port) +static void evtchn_unbind_from_user(struct per_user_data *u, + struct user_evtchn *evtchn) { - int irq = irq_from_evtchn(port); + int irq = irq_from_evtchn(evtchn->port); BUG_ON(irq < 0); - unbind_from_irqhandler(irq, (void *)(unsigned long)port); + unbind_from_irqhandler(irq, evtchn); - set_port_user(port, NULL); + del_evtchn(u, evtchn); } static long evtchn_ioctl(struct file *file, @@ -370,6 +411,7 @@ static long evtchn_ioctl(struct file *file, case IOCTL_EVTCHN_UNBIND: { struct ioctl_evtchn_unbind unbind; + struct user_evtchn *evtchn; rc = -EFAULT; if (copy_from_user(&unbind, uarg, sizeof(unbind))) @@ -380,29 +422,27 @@ static long evtchn_ioctl(struct file *file, break; rc = -ENOTCONN; - if (get_port_user(unbind.port) != u) + evtchn = find_evtchn(u, unbind.port); + if (!evtchn) break; disable_irq(irq_from_evtchn(unbind.port)); - - evtchn_unbind_from_user(u, unbind.port); - + evtchn_unbind_from_user(u, evtchn); rc = 0; break; } case IOCTL_EVTCHN_NOTIFY: { struct ioctl_evtchn_notify notify; + struct user_evtchn *evtchn; rc = -EFAULT; if (copy_from_user(¬ify, uarg, sizeof(notify))) break; - if (notify.port >= NR_EVENT_CHANNELS) { - rc = -EINVAL; - } else if (get_port_user(notify.port) != u) { - rc = -ENOTCONN; - } else { + rc = -ENOTCONN; + evtchn = find_evtchn(u, notify.port); + if (evtchn) { notify_remote_via_evtchn(notify.port); rc = 0; } @@ -412,9 +452,9 @@ static long evtchn_ioctl(struct file *file, case IOCTL_EVTCHN_RESET: { /* Initialise the ring to empty. Clear errors. */ mutex_lock(&u->ring_cons_mutex); - spin_lock_irq(&port_user_lock); + spin_lock_irq(&u->ring_prod_lock); u->ring_cons = u->ring_prod = u->ring_overflow = 0; - spin_unlock_irq(&port_user_lock); + spin_unlock_irq(&u->ring_prod_lock); mutex_unlock(&u->ring_cons_mutex); rc = 0; break; @@ -473,6 +513,7 @@ static int evtchn_open(struct inode *inode, struct file *filp) mutex_init(&u->bind_mutex); mutex_init(&u->ring_cons_mutex); + spin_lock_init(&u->ring_prod_lock); filp->private_data = u; @@ -481,15 +522,15 @@ static int evtchn_open(struct inode *inode, struct file *filp) static int evtchn_release(struct inode *inode, struct file *filp) { - int i; struct per_user_data *u = filp->private_data; + struct rb_node *node; - for (i = 0; i < NR_EVENT_CHANNELS; i++) { - if (get_port_user(i) != u) - continue; + while ((node = u->evtchns.rb_node)) { + struct user_evtchn *evtchn; - disable_irq(irq_from_evtchn(i)); - evtchn_unbind_from_user(get_port_user(i), i); + evtchn = rb_entry(node, struct user_evtchn, node); + disable_irq(irq_from_evtchn(evtchn->port)); + evtchn_unbind_from_user(u, evtchn); } free_page((unsigned long)u->ring); @@ -523,12 +564,6 @@ static int __init evtchn_init(void) if (!xen_domain()) return -ENODEV; - port_user = kcalloc(NR_EVENT_CHANNELS, sizeof(*port_user), GFP_KERNEL); - if (port_user == NULL) - return -ENOMEM; - - spin_lock_init(&port_user_lock); - /* Create '/dev/xen/evtchn'. */ err = misc_register(&evtchn_miscdev); if (err != 0) { @@ -543,9 +578,6 @@ static int __init evtchn_init(void) static void __exit evtchn_cleanup(void) { - kfree(port_user); - port_user = NULL; - misc_deregister(&evtchn_miscdev); }