sched: implement .init_pdata in Credit, Credit2 and RTDS

In fact, if a scheduler needs per-pCPU information,
that needs to be initialized appropriately. So, we take
the code that is performing initializations from (right
now) .alloc_pdata, and use it for .init_pdata, leaving
only actualy allocations in the former, if any (which
is the case in RTDS and Credit1).

On the other hand, in Credit2, since we don't really
need any per-pCPU data allocation, everything that was
being done in .alloc_pdata, is now done in .init_pdata.
And the fact that now .alloc_pdata can be left undefined,
allows us to just get rid of it.

Still for Credit2, the fact that .init_pdata is called
during CPU_STARTING (rather than CPU_UP_PREPARE) kills
the need for the scheduler to setup a similar callback
itself, simplifying the code.

And thanks to such simplification, it is now also ok to
move some of the logic meant at double checking that a
cpu was (or was not) initialized, into ASSERTS (rather
than an if() and a BUG_ON).

Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>
Reviewed-by: Meng Xu <mengxu@cis.upenn.edu>
Reviewed-by: George Dunlap <george.dunlap@eu.citrix.com>

xen/common/sched_credit.c

@@ -527,8 +527,6 @@ static void *
 csched_alloc_pdata(const struct scheduler *ops, int cpu)
 {
     struct csched_pcpu *spc;
-    struct csched_private *prv = CSCHED_PRIV(ops);
-    unsigned long flags;
 
     /* Allocate per-PCPU info */
     spc = xzalloc(struct csched_pcpu);
@@ -541,6 +539,19 @@ csched_alloc_pdata(const struct scheduler *ops, int cpu)
         return ERR_PTR(-ENOMEM);
     }
 
+    return spc;
+}
+
+static void
+csched_init_pdata(const struct scheduler *ops, void *pdata, int cpu)
+{
+    struct csched_private *prv = CSCHED_PRIV(ops);
+    struct csched_pcpu * const spc = pdata;
+    unsigned long flags;
+
+    /* cpu data needs to be allocated, but STILL uninitialized */
+    ASSERT(spc && spc->runq.next == NULL && spc->runq.prev == NULL);
+
     spin_lock_irqsave(&prv->lock, flags);
 
     /* Initialize/update system-wide config */
@@ -561,16 +572,12 @@ csched_alloc_pdata(const struct scheduler *ops, int cpu)
     INIT_LIST_HEAD(&spc->runq);
     spc->runq_sort_last = prv->runq_sort;
     spc->idle_bias = nr_cpu_ids - 1;
-    if ( per_cpu(schedule_data, cpu).sched_priv == NULL )
-        per_cpu(schedule_data, cpu).sched_priv = spc;
 
     /* Start off idling... */
     BUG_ON(!is_idle_vcpu(curr_on_cpu(cpu)));
     cpumask_set_cpu(cpu, prv->idlers);
 
     spin_unlock_irqrestore(&prv->lock, flags);
-
-    return spc;
 }
 
 #ifndef NDEBUG
@@ -2054,6 +2061,7 @@ static const struct scheduler sched_credit_def = {
     .alloc_vdata    = csched_alloc_vdata,
     .free_vdata     = csched_free_vdata,
     .alloc_pdata    = csched_alloc_pdata,
+    .init_pdata     = csched_init_pdata,
     .free_pdata     = csched_free_pdata,
     .alloc_domdata  = csched_alloc_domdata,
     .free_domdata   = csched_free_domdata,

xen/common/sched_credit2.c

@@ -1971,7 +1971,8 @@ static void deactivate_runqueue(struct csched2_private *prv, int rqi)
     cpumask_clear_cpu(rqi, &prv->active_queues);
 }
 
-static void init_pcpu(const struct scheduler *ops, int cpu)
+static void
+csched2_init_pdata(const struct scheduler *ops, void *pdata, int cpu)
 {
     unsigned rqi;
     unsigned long flags;
@@ -1981,12 +1982,7 @@ static void init_pcpu(const struct scheduler *ops, int cpu)
 
     spin_lock_irqsave(&prv->lock, flags);
 
-    if ( cpumask_test_cpu(cpu, &prv->initialized) )
-    {
-        printk("%s: Strange, cpu %d already initialized!\n", __func__, cpu);
-        spin_unlock_irqrestore(&prv->lock, flags);
-        return;
-    }
+    ASSERT(!cpumask_test_cpu(cpu, &prv->initialized));
 
     /* Figure out which runqueue to put it in */
     rqi = 0;
@@ -2036,20 +2032,6 @@ static void init_pcpu(const struct scheduler *ops, int cpu)
     return;
 }
 
-static void *
-csched2_alloc_pdata(const struct scheduler *ops, int cpu)
-{
-    /* Check to see if the cpu is online yet */
-    /* Note: cpu 0 doesn't get a STARTING callback */
-    if ( cpu == 0 || cpu_to_socket(cpu) != XEN_INVALID_SOCKET_ID )
-        init_pcpu(ops, cpu);
-    else
-        printk("%s: cpu %d not online yet, deferring initializatgion\n",
-               __func__, cpu);
-
-    return NULL;
-}
-
 static void
 csched2_free_pdata(const struct scheduler *ops, void *pcpu, int cpu)
 {
@@ -2061,7 +2043,7 @@ csched2_free_pdata(const struct scheduler *ops, void *pcpu, int cpu)
 
     spin_lock_irqsave(&prv->lock, flags);
 
-    BUG_ON(!cpumask_test_cpu(cpu, &prv->initialized));
+    ASSERT(cpumask_test_cpu(cpu, &prv->initialized));
     
     /* Find the old runqueue and remove this cpu from it */
     rqi = prv->runq_map[cpu];
@@ -2098,49 +2080,6 @@ csched2_free_pdata(const struct scheduler *ops, void *pcpu, int cpu)
     return;
 }
 
-static int
-csched2_cpu_starting(int cpu)
-{
-    struct scheduler *ops;
-
-    /* Hope this is safe from cpupools switching things around. :-) */
-    ops = per_cpu(scheduler, cpu);
-
-    if ( ops->alloc_pdata == csched2_alloc_pdata )
-        init_pcpu(ops, cpu);
-
-    return NOTIFY_DONE;
-}
-
-static int cpu_credit2_callback(
-    struct notifier_block *nfb, unsigned long action, void *hcpu)
-{
-    unsigned int cpu = (unsigned long)hcpu;
-    int rc = 0;
-
-    switch ( action )
-    {
-    case CPU_STARTING:
-        csched2_cpu_starting(cpu);
-        break;
-    default:
-        break;
-    }
-
-    return !rc ? NOTIFY_DONE : notifier_from_errno(rc);
-}
-
-static struct notifier_block cpu_credit2_nfb = {
-    .notifier_call = cpu_credit2_callback
-};
-
-static int
-csched2_global_init(void)
-{
-    register_cpu_notifier(&cpu_credit2_nfb);
-    return 0;
-}
-
 static int
 csched2_init(struct scheduler *ops)
 {
@@ -2219,12 +2158,11 @@ static const struct scheduler sched_credit2_def = {
 
     .dump_cpu_state = csched2_dump_pcpu,
     .dump_settings  = csched2_dump,
-    .global_init    = csched2_global_init,
     .init           = csched2_init,
     .deinit         = csched2_deinit,
     .alloc_vdata    = csched2_alloc_vdata,
     .free_vdata     = csched2_free_vdata,
-    .alloc_pdata    = csched2_alloc_pdata,
+    .init_pdata     = csched2_init_pdata,
     .free_pdata     = csched2_free_pdata,
     .alloc_domdata  = csched2_alloc_domdata,
     .free_domdata   = csched2_free_domdata,

xen/common/sched_rt.c

@@ -666,8 +666,8 @@ rt_deinit(struct scheduler *ops)
  * Point per_cpu spinlock to the global system lock;
  * All cpu have same global system lock
  */
-static void *
-rt_alloc_pdata(const struct scheduler *ops, int cpu)
+static void
+rt_init_pdata(const struct scheduler *ops, void *pdata, int cpu)
 {
     struct rt_private *prv = rt_priv(ops);
     spinlock_t *old_lock;
@@ -680,6 +680,12 @@ rt_alloc_pdata(const struct scheduler *ops, int cpu)
 
     /* _Not_ pcpu_schedule_unlock(): per_cpu().schedule_lock changed! */
     spin_unlock_irqrestore(old_lock, flags);
+}
+
+static void *
+rt_alloc_pdata(const struct scheduler *ops, int cpu)
+{
+    struct rt_private *prv = rt_priv(ops);
 
     if ( !alloc_cpumask_var(&_cpumask_scratch[cpu]) )
         return ERR_PTR(-ENOMEM);
@@ -1461,6 +1467,7 @@ static const struct scheduler sched_rtds_def = {
     .deinit         = rt_deinit,
     .alloc_pdata    = rt_alloc_pdata,
     .free_pdata     = rt_free_pdata,
+    .init_pdata     = rt_init_pdata,
     .alloc_domdata  = rt_alloc_domdata,
     .free_domdata   = rt_free_domdata,
     .init_domain    = rt_dom_init,