[PATCH] percpu: convert timers

Patch from Dipankar Sarma <dipankar@in.ibm.com>

This patch changes the per-CPU data in timer management (tvec_bases)
to use per_cpu data area and makes it safe for cpu_possible allocation
by using CPU notifiers. End result - saving space.

Depends on cpu_possible patch.

diff --git a/kernel/timer.c b/kernel/timer.c
index 58c80293060b156bc43cf33a6accd393a2fe7943..ebb2b6c627cc031857a77737fafc407555301232 100644 (file)
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -24,6 +24,7 @@
 #include <linux/percpu.h>
 #include <linux/init.h>
 #include <linux/mm.h>
+#include <linux/notifier.h>
 
 #include <asm/uaccess.h>
 
@@ -62,7 +63,8 @@ struct tvec_t_base_s {
 
 typedef struct tvec_t_base_s tvec_base_t;
 
-static tvec_base_t tvec_bases[NR_CPUS] __cacheline_aligned;
+/* Fake initialization */
+static DEFINE_PER_CPU(tvec_base_t, tvec_bases) = { SPIN_LOCK_UNLOCKED };
 
 /* Fake initialization needed to avoid compiler breakage */
 static DEFINE_PER_CPU(struct tasklet_struct, timer_tasklet) = { NULL };
@@ -122,7 +124,7 @@ static inline void internal_add_timer(tvec_base_t *base, timer_t *timer)
 void add_timer(timer_t *timer)
 {
        int cpu = get_cpu();
-       tvec_base_t *base = tvec_bases + cpu;
+       tvec_base_t *base = &per_cpu(tvec_bases, cpu);
        unsigned long flags;
   
        BUG_ON(timer_pending(timer) || !timer->function);
@@ -143,7 +145,7 @@ void add_timer(timer_t *timer)
  */
 void add_timer_on(struct timer_list *timer, int cpu)
 {
-       tvec_base_t *base = tvec_bases+ cpu;
+       tvec_base_t *base = &per_cpu(tvec_bases, cpu);
        unsigned long flags;
   
        BUG_ON(timer_pending(timer) || !timer->function);
@@ -189,7 +191,7 @@ int mod_timer(timer_t *timer, unsigned long expires)
                return 1;
 
        local_irq_save(flags);
-       new_base = tvec_bases + smp_processor_id();
+       new_base = &per_cpu(tvec_bases, smp_processor_id());
 repeat:
        old_base = timer->base;
 
@@ -285,15 +287,17 @@ repeat:
  */
 int del_timer_sync(timer_t *timer)
 {
-       tvec_base_t *base = tvec_bases;
+       tvec_base_t *base;
        int i, ret = 0;
 
 del_again:
        ret += del_timer(timer);
 
-       for (i = 0; i < NR_CPUS; i++, base++) {
+       for (i = 0; i < NR_CPUS; i++) {
                if (!cpu_online(i))
                        continue;
+
+               base = &per_cpu(tvec_bases, i);
                if (base->running_timer == timer) {
                        while (base->running_timer == timer) {
                                cpu_relax();
@@ -731,7 +735,7 @@ unsigned long last_time_offset;
  */
 static void run_timer_tasklet(unsigned long data)
 {
-       tvec_base_t *base = tvec_bases + smp_processor_id();
+       tvec_base_t *base = &per_cpu(tvec_bases, smp_processor_id());
 
        if ((long)(jiffies - base->timer_jiffies) >= 0)
                __run_timers(base);
@@ -1086,23 +1090,46 @@ out:
        return 0;
 }
 
-void __init init_timers(void)
+static void __devinit init_timers_cpu(int cpu)
 {
-       int i, j;
-
-       for (i = 0; i < NR_CPUS; i++) {
-               tvec_base_t *base;
-              
-               base = tvec_bases + i;
-               spin_lock_init(&base->lock);
-               for (j = 0; j < TVN_SIZE; j++) {
-                       INIT_LIST_HEAD(base->tv5.vec + j);
-                       INIT_LIST_HEAD(base->tv4.vec + j);
-                       INIT_LIST_HEAD(base->tv3.vec + j);
-                       INIT_LIST_HEAD(base->tv2.vec + j);
-               }
-               for (j = 0; j < TVR_SIZE; j++)
-                       INIT_LIST_HEAD(base->tv1.vec + j);
-               tasklet_init(&per_cpu(timer_tasklet, i), run_timer_tasklet, 0);
+       int j;
+       tvec_base_t *base;
+       
+       base = &per_cpu(tvec_bases, cpu);
+       spin_lock_init(&base->lock);
+       for (j = 0; j < TVN_SIZE; j++) {
+               INIT_LIST_HEAD(base->tv5.vec + j);
+               INIT_LIST_HEAD(base->tv4.vec + j);
+               INIT_LIST_HEAD(base->tv3.vec + j);
+               INIT_LIST_HEAD(base->tv2.vec + j);
+       }
+       for (j = 0; j < TVR_SIZE; j++)
+               INIT_LIST_HEAD(base->tv1.vec + j);
+       tasklet_init(&per_cpu(timer_tasklet, cpu), run_timer_tasklet, 0UL);
+}
+       
+static int __devinit timer_cpu_notify(struct notifier_block *self, 
+                               unsigned long action, void *hcpu)
+{
+       long cpu = (long)hcpu;
+       switch(action) {
+       case CPU_UP_PREPARE:
+               init_timers_cpu(cpu);
+               break;
+       default:
+               break;
        }
+       return NOTIFY_OK;
+}
+
+static struct notifier_block __devinitdata timers_nb = {
+       .notifier_call  = timer_cpu_notify,
+};
+
+
+void __init init_timers(void)
+{
+       timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,
+                               (void *)(long)smp_processor_id());
+       register_cpu_notifier(&timers_nb);
 }