SGI Altix mmtimer: allow larger number of timers per node

The purpose of this patch to the SGI Altix specific mmtimer (posix timer)
driver is to allow a virtually infinite number of timers to be set per
node.

Timers will now be kept on a sorted per-node list and a single node-based
hardware comparator is used to trigger the next timer.

[akpm@linux-foundation.org: mark things static]
[akpm@linux-foundation.org: fix warning]
Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 244 insertions, 156 deletions

diff --git a/drivers/char/mmtimer.c b/drivers/char/mmtimer.c
index e60a74c66e3d..d83db5d880e0 100644
--- a/drivers/char/mmtimer.c
+++ b/drivers/char/mmtimer.c
@@ -74,9 +74,8 @@ static const struct file_operations mmtimer_fops = {
  * We only have comparison registers RTC1-4 currently available per
  * node.  RTC0 is used by SAL.
  */
-#define NUM_COMPARATORS 3
 /* Check for an RTC interrupt pending */
-static int inline mmtimer_int_pending(int comparator)
+static int mmtimer_int_pending(int comparator)
 {
         if (HUB_L((unsigned long *)LOCAL_MMR_ADDR(SH_EVENT_OCCURRED)) &
                         SH_EVENT_OCCURRED_RTC1_INT_MASK << comparator)
@@ -84,15 +83,16 @@ static int inline mmtimer_int_pending(int comparator)
         else
                 return 0;
 }
+
 /* Clear the RTC interrupt pending bit */
-static void inline mmtimer_clr_int_pending(int comparator)
+static void mmtimer_clr_int_pending(int comparator)
 {
         HUB_S((u64 *)LOCAL_MMR_ADDR(SH_EVENT_OCCURRED_ALIAS),
                 SH_EVENT_OCCURRED_RTC1_INT_MASK << comparator);
 }
 
 /* Setup timer on comparator RTC1 */
-static void inline mmtimer_setup_int_0(u64 expires)
+static void mmtimer_setup_int_0(int cpu, u64 expires)
 {
         u64 val;
 
@@ -106,7 +106,7 @@ static void inline mmtimer_setup_int_0(u64 expires)
         mmtimer_clr_int_pending(0);
 
         val = ((u64)SGI_MMTIMER_VECTOR << SH_RTC1_INT_CONFIG_IDX_SHFT) |
-                ((u64)cpu_physical_id(smp_processor_id()) <<
+                ((u64)cpu_physical_id(cpu) <<
                         SH_RTC1_INT_CONFIG_PID_SHFT);
 
         /* Set configuration */
@@ -122,7 +122,7 @@ static void inline mmtimer_setup_int_0(u64 expires)
 }
 
 /* Setup timer on comparator RTC2 */
-static void inline mmtimer_setup_int_1(u64 expires)
+static void mmtimer_setup_int_1(int cpu, u64 expires)
 {
         u64 val;
 
@@ -133,7 +133,7 @@ static void inline mmtimer_setup_int_1(u64 expires)
         mmtimer_clr_int_pending(1);
 
         val = ((u64)SGI_MMTIMER_VECTOR << SH_RTC2_INT_CONFIG_IDX_SHFT) |
-                ((u64)cpu_physical_id(smp_processor_id()) <<
+                ((u64)cpu_physical_id(cpu) <<
                         SH_RTC2_INT_CONFIG_PID_SHFT);
 
         HUB_S((u64 *)LOCAL_MMR_ADDR(SH_RTC2_INT_CONFIG), val);
@@ -144,7 +144,7 @@ static void inline mmtimer_setup_int_1(u64 expires)
 }
 
 /* Setup timer on comparator RTC3 */
-static void inline mmtimer_setup_int_2(u64 expires)
+static void mmtimer_setup_int_2(int cpu, u64 expires)
 {
         u64 val;
 
@@ -155,7 +155,7 @@ static void inline mmtimer_setup_int_2(u64 expires)
         mmtimer_clr_int_pending(2);
 
         val = ((u64)SGI_MMTIMER_VECTOR << SH_RTC3_INT_CONFIG_IDX_SHFT) |
-                ((u64)cpu_physical_id(smp_processor_id()) <<
+                ((u64)cpu_physical_id(cpu) <<
                         SH_RTC3_INT_CONFIG_PID_SHFT);
 
         HUB_S((u64 *)LOCAL_MMR_ADDR(SH_RTC3_INT_CONFIG), val);
@@ -170,22 +170,22 @@ static void inline mmtimer_setup_int_2(u64 expires)
  * in order to insure that the setup succeeds in a deterministic time frame.
  * It will check if the interrupt setup succeeded.
  */
-static int inline mmtimer_setup(int comparator, unsigned long expires)
+static int mmtimer_setup(int cpu, int comparator, unsigned long expires)
 {
 
         switch (comparator) {
         case 0:
-                mmtimer_setup_int_0(expires);
+                mmtimer_setup_int_0(cpu, expires);
                 break;
         case 1:
-                mmtimer_setup_int_1(expires);
+                mmtimer_setup_int_1(cpu, expires);
                 break;
         case 2:
-                mmtimer_setup_int_2(expires);
+                mmtimer_setup_int_2(cpu, expires);
                 break;
         }
         /* We might've missed our expiration time */
-        if (rtc_time() < expires)
+        if (rtc_time() <= expires)
                 return 1;
 
         /*
@@ -195,7 +195,7 @@ static int inline mmtimer_setup(int comparator, unsigned long expires)
         return mmtimer_int_pending(comparator);
 }
 
-static int inline mmtimer_disable_int(long nasid, int comparator)
+static int mmtimer_disable_int(long nasid, int comparator)
 {
         switch (comparator) {
         case 0:
@@ -216,18 +216,124 @@ static int inline mmtimer_disable_int(long nasid, int comparator)
         return 0;
 }
 
-#define TIMER_OFF 0xbadcabLL
+#define COMPARATOR      1               /* The comparator to use */
 
-/* There is one of these for each comparator */
-typedef struct mmtimer {
-        spinlock_t lock ____cacheline_aligned;
+#define TIMER_OFF       0xbadcabLL      /* Timer is not setup */
+#define TIMER_SET       0               /* Comparator is set for this timer */
+
+/* There is one of these for each timer */
+struct mmtimer {
+        struct rb_node list;
         struct k_itimer *timer;
-        int i;
         int cpu;
+};
+
+struct mmtimer_node {
+        spinlock_t lock ____cacheline_aligned;
+        struct rb_root timer_head;
+        struct rb_node *next;
         struct tasklet_struct tasklet;
-} mmtimer_t;
+};
+static struct mmtimer_node *timers;
+
+
+/*
+ * Add a new mmtimer struct to the node's mmtimer list.
+ * This function assumes the struct mmtimer_node is locked.
+ */
+static void mmtimer_add_list(struct mmtimer *n)
+{
+        int nodeid = n->timer->it.mmtimer.node;
+        unsigned long expires = n->timer->it.mmtimer.expires;
+        struct rb_node **link = &timers[nodeid].timer_head.rb_node;
+        struct rb_node *parent = NULL;
+        struct mmtimer *x;
+
+        /*
+         * Find the right place in the rbtree:
+         */
+        while (*link) {
+                parent = *link;
+                x = rb_entry(parent, struct mmtimer, list);
+
+                if (expires < x->timer->it.mmtimer.expires)
+                        link = &(*link)->rb_left;
+                else
+                        link = &(*link)->rb_right;
+        }
+
+        /*
+         * Insert the timer to the rbtree and check whether it
+         * replaces the first pending timer
+         */
+        rb_link_node(&n->list, parent, link);
+        rb_insert_color(&n->list, &timers[nodeid].timer_head);
+
+        if (!timers[nodeid].next || expires < rb_entry(timers[nodeid].next,
+                        struct mmtimer, list)->timer->it.mmtimer.expires)
+                timers[nodeid].next = &n->list;
+}
+
+/*
+ * Set the comparator for the next timer.
+ * This function assumes the struct mmtimer_node is locked.
+ */
+static void mmtimer_set_next_timer(int nodeid)
+{
+        struct mmtimer_node *n = &timers[nodeid];
+        struct mmtimer *x;
+        struct k_itimer *t;
+        int o;
+
+restart:
+        if (n->next == NULL)
+                return;
 
-static mmtimer_t ** timers;
+        x = rb_entry(n->next, struct mmtimer, list);
+        t = x->timer;
+        if (!t->it.mmtimer.incr) {
+                /* Not an interval timer */
+                if (!mmtimer_setup(x->cpu, COMPARATOR,
+                                        t->it.mmtimer.expires)) {
+                        /* Late setup, fire now */
+                        tasklet_schedule(&n->tasklet);
+                }
+                return;
+        }
+
+        /* Interval timer */
+        o = 0;
+        while (!mmtimer_setup(x->cpu, COMPARATOR, t->it.mmtimer.expires)) {
+                unsigned long e, e1;
+                struct rb_node *next;
+                t->it.mmtimer.expires += t->it.mmtimer.incr << o;
+                t->it_overrun += 1 << o;
+                o++;
+                if (o > 20) {
+                        printk(KERN_ALERT "mmtimer: cannot reschedule timer\n");
+                        t->it.mmtimer.clock = TIMER_OFF;
+                        n->next = rb_next(&x->list);
+                        rb_erase(&x->list, &n->timer_head);
+                        kfree(x);
+                        goto restart;
+                }
+
+                e = t->it.mmtimer.expires;
+                next = rb_next(&x->list);
+
+                if (next == NULL)
+                        continue;
+
+                e1 = rb_entry(next, struct mmtimer, list)->
+                        timer->it.mmtimer.expires;
+                if (e > e1) {
+                        n->next = next;
+                        rb_erase(&x->list, &n->timer_head);
+                        mmtimer_add_list(x);
+                        goto restart;
+                }
+        }
+}
 
 /**
  * mmtimer_ioctl - ioctl interface for /dev/mmtimer
@@ -390,35 +496,6 @@ static int sgi_clock_set(clockid_t clockid, struct timespec *tp)
         return 0;
 }
 
-/*
- * Schedule the next periodic interrupt. This function will attempt
- * to schedule a periodic interrupt later if necessary. If the scheduling
- * of an interrupt fails then the time to skip is lengthened
- * exponentially in order to ensure that the next interrupt
- * can be properly scheduled..
- */
-static int inline reschedule_periodic_timer(mmtimer_t *x)
-{
-        int n;
-        struct k_itimer *t = x->timer;
-
-        t->it.mmtimer.clock = x->i;
-        t->it_overrun--;
-
-        n = 0;
-        do {
-
-                t->it.mmtimer.expires += t->it.mmtimer.incr << n;
-                t->it_overrun += 1 << n;
-                n++;
-                if (n > 20)
-                        return 1;
-
-        } while (!mmtimer_setup(x->i, t->it.mmtimer.expires));
-
-        return 0;
-}
-
 /**
  * mmtimer_interrupt - timer interrupt handler
  * @irq: irq received
@@ -435,71 +512,75 @@ static int inline reschedule_periodic_timer(mmtimer_t *x)
 static irqreturn_t
 mmtimer_interrupt(int irq, void *dev_id)
 {
-        int i;
         unsigned long expires = 0;
         int result = IRQ_NONE;
         unsigned indx = cpu_to_node(smp_processor_id());
+        struct mmtimer *base;
 
-        /*
-         * Do this once for each comparison register
-         */
-        for (i = 0; i < NUM_COMPARATORS; i++) {
-                mmtimer_t *base = timers[indx] + i;
-                /* Make sure this doesn't get reused before tasklet_sched */
-                spin_lock(&base->lock);
-                if (base->cpu == smp_processor_id()) {
-                        if (base->timer)
-                                expires = base->timer->it.mmtimer.expires;
-                        /* expires test won't work with shared irqs */
-                        if ((mmtimer_int_pending(i) > 0) ||
-                                (expires && (expires < rtc_time()))) {
-                                mmtimer_clr_int_pending(i);
-                                tasklet_schedule(&base->tasklet);
-                                result = IRQ_HANDLED;
-                        }
+        spin_lock(&timers[indx].lock);
+        base = rb_entry(timers[indx].next, struct mmtimer, list);
+        if (base == NULL) {
+                spin_unlock(&timers[indx].lock);
+                return result;
+        }
+
+        if (base->cpu == smp_processor_id()) {
+                if (base->timer)
+                        expires = base->timer->it.mmtimer.expires;
+                /* expires test won't work with shared irqs */
+                if ((mmtimer_int_pending(COMPARATOR) > 0) ||
+                        (expires && (expires <= rtc_time()))) {
+                        mmtimer_clr_int_pending(COMPARATOR);
+                        tasklet_schedule(&timers[indx].tasklet);
+                        result = IRQ_HANDLED;
                 }
-                spin_unlock(&base->lock);
-                expires = 0;
         }
+        spin_unlock(&timers[indx].lock);
         return result;
 }
 
-void mmtimer_tasklet(unsigned long data) {
-        mmtimer_t *x = (mmtimer_t *)data;
-        struct k_itimer *t = x->timer;
+static void mmtimer_tasklet(unsigned long data)
+{
+        int nodeid = data;
+        struct mmtimer_node *mn = &timers[nodeid];
+        struct mmtimer *x = rb_entry(mn->next, struct mmtimer, list);
+        struct k_itimer *t;
         unsigned long flags;
 
-        if (t == NULL)
-                return;
-
         /* Send signal and deal with periodic signals */
-        spin_lock_irqsave(&t->it_lock, flags);
-        spin_lock(&x->lock);
-        /* If timer was deleted between interrupt and here, leave */
-        if (t != x->timer)
+        spin_lock_irqsave(&mn->lock, flags);
+        if (!mn->next)
                 goto out;
-        t->it_overrun = 0;
 
-        if (posix_timer_event(t, 0) != 0) {
+        x = rb_entry(mn->next, struct mmtimer, list);
+        t = x->timer;
+
+        if (t->it.mmtimer.clock == TIMER_OFF)
+                goto out;
+
+        t->it_overrun = 0;
 
-                // printk(KERN_WARNING "mmtimer: cannot deliver signal.\n");
+        mn->next = rb_next(&x->list);
+        rb_erase(&x->list, &mn->timer_head);
 
+        if (posix_timer_event(t, 0) != 0)
                 t->it_overrun++;
-        }
+
         if(t->it.mmtimer.incr) {
-                /* Periodic timer */
-                if (reschedule_periodic_timer(x)) {
-                        printk(KERN_WARNING "mmtimer: unable to reschedule\n");
-                        x->timer = NULL;
-                }
+                t->it.mmtimer.expires += t->it.mmtimer.incr;
+                mmtimer_add_list(x);
         } else {
                 /* Ensure we don't false trigger in mmtimer_interrupt */
+                t->it.mmtimer.clock = TIMER_OFF;
                 t->it.mmtimer.expires = 0;
+                kfree(x);
         }
+        /* Set comparator for next timer, if there is one */
+        mmtimer_set_next_timer(nodeid);
+
         t->it_overrun_last = t->it_overrun;
 out:
-        spin_unlock(&x->lock);
-        spin_unlock_irqrestore(&t->it_lock, flags);
+        spin_unlock_irqrestore(&mn->lock, flags);
 }
 
 static int sgi_timer_create(struct k_itimer *timer)
@@ -516,19 +597,50 @@ static int sgi_timer_create(struct k_itimer *timer)
  */
 static int sgi_timer_del(struct k_itimer *timr)
 {
-        int i = timr->it.mmtimer.clock;
         cnodeid_t nodeid = timr->it.mmtimer.node;
-        mmtimer_t *t = timers[nodeid] + i;
         unsigned long irqflags;
 
-        if (i != TIMER_OFF) {
-                spin_lock_irqsave(&t->lock, irqflags);
-                mmtimer_disable_int(cnodeid_to_nasid(nodeid),i);
-                t->timer = NULL;
+        spin_lock_irqsave(&timers[nodeid].lock, irqflags);
+        if (timr->it.mmtimer.clock != TIMER_OFF) {
+                unsigned long expires = timr->it.mmtimer.expires;
+                struct rb_node *n = timers[nodeid].timer_head.rb_node;
+                struct mmtimer *uninitialized_var(t);
+                int r = 0;
+
                 timr->it.mmtimer.clock = TIMER_OFF;
                 timr->it.mmtimer.expires = 0;
-                spin_unlock_irqrestore(&t->lock, irqflags);
+
+                while (n) {
+                        t = rb_entry(n, struct mmtimer, list);
+                        if (t->timer == timr)
+                                break;
+
+                        if (expires < t->timer->it.mmtimer.expires)
+                                n = n->rb_left;
+                        else
+                                n = n->rb_right;
+                }
+
+                if (!n) {
+                        spin_unlock_irqrestore(&timers[nodeid].lock, irqflags);
+                        return 0;
+                }
+
+                if (timers[nodeid].next == n) {
+                        timers[nodeid].next = rb_next(n);
+                        r = 1;
+                }
+
+                rb_erase(n, &timers[nodeid].timer_head);
+                kfree(t);
+
+                if (r) {
+                        mmtimer_disable_int(cnodeid_to_nasid(nodeid),
+                                COMPARATOR);
+                        mmtimer_set_next_timer(nodeid);
+                }
         }
+        spin_unlock_irqrestore(&timers[nodeid].lock, irqflags);
         return 0;
 }
 
@@ -557,12 +669,11 @@ static int sgi_timer_set(struct k_itimer *timr, int flags,
         struct itimerspec * new_setting,
         struct itimerspec * old_setting)
 {
-
-        int i;
         unsigned long when, period, irqflags;
         int err = 0;
         cnodeid_t nodeid;
-        mmtimer_t *base;
+        struct mmtimer *base;
+        struct rb_node *n;
 
         if (old_setting)
                 sgi_timer_get(timr, old_setting);
@@ -575,6 +686,10 @@ static int sgi_timer_set(struct k_itimer *timr, int flags,
                 /* Clear timer */
                 return 0;
 
+        base = kmalloc(sizeof(struct mmtimer), GFP_KERNEL);
+        if (base == NULL)
+                return -ENOMEM;
+
         if (flags & TIMER_ABSTIME) {
                 struct timespec n;
                 unsigned long now;
@@ -604,47 +719,38 @@ static int sgi_timer_set(struct k_itimer *timr, int flags,
         preempt_disable();
 
         nodeid =  cpu_to_node(smp_processor_id());
-retry:
-        /* Don't use an allocated timer, or a deleted one that's pending */
-        for(i = 0; i< NUM_COMPARATORS; i++) {
-                base = timers[nodeid] + i;
-                if (!base->timer && !base->tasklet.state) {
-                        break;
-                }
-        }
-
-        if (i == NUM_COMPARATORS) {
-                preempt_enable();
-                return -EBUSY;
-        }
 
-        spin_lock_irqsave(&base->lock, irqflags);
+        /* Lock the node timer structure */
+        spin_lock_irqsave(&timers[nodeid].lock, irqflags);
 
-        if (base->timer || base->tasklet.state != 0) {
-                spin_unlock_irqrestore(&base->lock, irqflags);
-                goto retry;
-        }
         base->timer = timr;
         base->cpu = smp_processor_id();
 
-        timr->it.mmtimer.clock = i;
+        timr->it.mmtimer.clock = TIMER_SET;
         timr->it.mmtimer.node = nodeid;
         timr->it.mmtimer.incr = period;
         timr->it.mmtimer.expires = when;
 
-        if (period == 0) {
-                if (!mmtimer_setup(i, when)) {
-                        mmtimer_disable_int(-1, i);
-                        posix_timer_event(timr, 0);
-                        timr->it.mmtimer.expires = 0;
-                }
-        } else {
-                timr->it.mmtimer.expires -= period;
-                if (reschedule_periodic_timer(base))
-                        err = -EINVAL;
+        n = timers[nodeid].next;
+
+        /* Add the new struct mmtimer to node's timer list */
+        mmtimer_add_list(base);
+
+        if (timers[nodeid].next == n) {
+                /* No need to reprogram comparator for now */
+                spin_unlock_irqrestore(&timers[nodeid].lock, irqflags);
+                preempt_enable();
+                return err;
         }
 
-        spin_unlock_irqrestore(&base->lock, irqflags);
+        /* We need to reprogram the comparator */
+        if (n)
+                mmtimer_disable_int(cnodeid_to_nasid(nodeid), COMPARATOR);
+
+        mmtimer_set_next_timer(nodeid);
+
+        /* Unlock the node timer structure */
+        spin_unlock_irqrestore(&timers[nodeid].lock, irqflags);
 
         preempt_enable();
 
@@ -669,7 +775,6 @@ static struct k_clock sgi_clock = {
  */
 static int __init mmtimer_init(void)
 {
-        unsigned i;
         cnodeid_t node, maxn = -1;
 
         if (!ia64_platform_is("sn2"))
@@ -706,31 +811,18 @@ static int __init mmtimer_init(void)
         maxn++;
 
         /* Allocate list of node ptrs to mmtimer_t's */
-        timers = kzalloc(sizeof(mmtimer_t *)*maxn, GFP_KERNEL);
+        timers = kzalloc(sizeof(struct mmtimer_node)*maxn, GFP_KERNEL);
         if (timers == NULL) {
                 printk(KERN_ERR "%s: failed to allocate memory for device\n",
                                 MMTIMER_NAME);
                 goto out3;
         }
 
-        /* Allocate mmtimer_t's for each online node */
+        /* Initialize struct mmtimer's for each online node */
         for_each_online_node(node) {
-                timers[node] = kmalloc_node(sizeof(mmtimer_t)*NUM_COMPARATORS, GFP_KERNEL, node);
-                if (timers[node] == NULL) {
-                        printk(KERN_ERR "%s: failed to allocate memory for device\n",
-                                MMTIMER_NAME);
-                        goto out4;
-                }
-                for (i=0; i< NUM_COMPARATORS; i++) {
-                        mmtimer_t * base = timers[node] + i;
-
-                        spin_lock_init(&base->lock);
-                        base->timer = NULL;
-                        base->cpu = 0;
-                        base->i = i;
-                        tasklet_init(&base->tasklet, mmtimer_tasklet,
-                                (unsigned long) (base));
-                }
+                spin_lock_init(&timers[node].lock);
+                tasklet_init(&timers[node].tasklet, mmtimer_tasklet,
+                        (unsigned long) node);
         }
 
         sgi_clock_period = sgi_clock.res = NSEC_PER_SEC / sn_rtc_cycles_per_second;
@@ -741,11 +833,8 @@ static int __init mmtimer_init(void)
 
         return 0;
 
-out4:
-        for_each_online_node(node) {
-                kfree(timers[node]);
-        }
 out3:
+        kfree(timers);
         misc_deregister(&mmtimer_miscdev);
 out2:
         free_irq(SGI_MMTIMER_VECTOR, NULL);
@@ -754,4 +843,3 @@ out1:
 }
 
 module_init(mmtimer_init);
-