cpumask: convert RCU implementations

Impact: use new cpumask API.

rcu_ctrlblk contains a cpumask, and it's highly optimized so I don't want
a cpumask_var_t (ie. a pointer) for the CONFIG_CPUMASK_OFFSTACK case.  It
could use a dangling bitmap, and be allocated in __rcu_init to save memory,
but for the moment we use a bitmap.

(Eventually 'struct cpumask' will be undefined for CONFIG_CPUMASK_OFFSTACK,
so we use a bitmap here to show we really mean it).

We remove on-stack cpumasks, using cpumask_var_t for
rcu_torture_shuffle_tasks() and for_each_cpu_and in force_quiescent_state().

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

3 files changed, 42 insertions, 36 deletions

diff --git a/kernel/rcuclassic.c b/kernel/rcuclassic.c
index e503a002f330..0ff9b05706a6 100644
--- a/kernel/rcuclassic.c
+++ b/kernel/rcuclassic.c
@@ -63,14 +63,14 @@ static struct rcu_ctrlblk rcu_ctrlblk = {
         .completed = -300,
         .pending = -300,
         .lock = __SPIN_LOCK_UNLOCKED(&rcu_ctrlblk.lock),
-        .cpumask = CPU_MASK_NONE,
+        .cpumask = CPU_BITS_NONE,
 };
 static struct rcu_ctrlblk rcu_bh_ctrlblk = {
         .cur = -300,
         .completed = -300,
         .pending = -300,
         .lock = __SPIN_LOCK_UNLOCKED(&rcu_bh_ctrlblk.lock),
-        .cpumask = CPU_MASK_NONE,
+        .cpumask = CPU_BITS_NONE,
 };
 
 DEFINE_PER_CPU(struct rcu_data, rcu_data) = { 0L };
@@ -85,7 +85,6 @@ static void force_quiescent_state(struct rcu_data *rdp,
                         struct rcu_ctrlblk *rcp)
 {
         int cpu;
-        cpumask_t cpumask;
         unsigned long flags;
 
         set_need_resched();
@@ -96,10 +95,10 @@ static void force_quiescent_state(struct rcu_data *rdp,
                  * Don't send IPI to itself. With irqs disabled,
                  * rdp->cpu is the current cpu.
                  *
-                 * cpu_online_map is updated by the _cpu_down()
+                 * cpu_online_mask is updated by the _cpu_down()
                  * using __stop_machine(). Since we're in irqs disabled
                  * section, __stop_machine() is not exectuting, hence
-                 * the cpu_online_map is stable.
+                 * the cpu_online_mask is stable.
                  *
                  * However,  a cpu might have been offlined _just_ before
                  * we disabled irqs while entering here.
@@ -107,13 +106,14 @@ static void force_quiescent_state(struct rcu_data *rdp,
                  * notification, leading to the offlined cpu's bit
                  * being set in the rcp->cpumask.
                  *
-                 * Hence cpumask = (rcp->cpumask & cpu_online_map) to prevent
+                 * Hence cpumask = (rcp->cpumask & cpu_online_mask) to prevent
                  * sending smp_reschedule() to an offlined CPU.
                  */
-                cpus_and(cpumask, rcp->cpumask, cpu_online_map);
-                cpu_clear(rdp->cpu, cpumask);
-                for_each_cpu_mask_nr(cpu, cpumask)
-                        smp_send_reschedule(cpu);
+                for_each_cpu_and(cpu,
+                                  to_cpumask(rcp->cpumask), cpu_online_mask) {
+                        if (cpu != rdp->cpu)
+                                smp_send_reschedule(cpu);
+                }
         }
         spin_unlock_irqrestore(&rcp->lock, flags);
 }
@@ -193,7 +193,7 @@ static void print_other_cpu_stall(struct rcu_ctrlblk *rcp)
 
         printk(KERN_ERR "INFO: RCU detected CPU stalls:");
         for_each_possible_cpu(cpu) {
-                if (cpu_isset(cpu, rcp->cpumask))
+                if (cpumask_test_cpu(cpu, to_cpumask(rcp->cpumask)))
                         printk(" %d", cpu);
         }
         printk(" (detected by %d, t=%ld jiffies)\n",
@@ -221,7 +221,8 @@ static void check_cpu_stall(struct rcu_ctrlblk *rcp)
         long delta;
 
         delta = jiffies - rcp->jiffies_stall;
-        if (cpu_isset(smp_processor_id(), rcp->cpumask) && delta >= 0) {
+        if (cpumask_test_cpu(smp_processor_id(), to_cpumask(rcp->cpumask)) &&
+                delta >= 0) {
 
                 /* We haven't checked in, so go dump stack. */
                 print_cpu_stall(rcp);
@@ -393,7 +394,8 @@ static void rcu_start_batch(struct rcu_ctrlblk *rcp)
                  * unnecessarily.
                  */
                 smp_mb();
-                cpus_andnot(rcp->cpumask, cpu_online_map, nohz_cpu_mask);
+                cpumask_andnot(to_cpumask(rcp->cpumask),
+                               cpu_online_mask, &nohz_cpu_mask);
 
                 rcp->signaled = 0;
         }
@@ -406,8 +408,8 @@ static void rcu_start_batch(struct rcu_ctrlblk *rcp)
  */
 static void cpu_quiet(int cpu, struct rcu_ctrlblk *rcp)
 {
-        cpu_clear(cpu, rcp->cpumask);
-        if (cpus_empty(rcp->cpumask)) {
+        cpumask_clear_cpu(cpu, to_cpumask(rcp->cpumask));
+        if (cpumask_empty(to_cpumask(rcp->cpumask))) {
                 /* batch completed ! */
                 rcp->completed = rcp->cur;
                 rcu_start_batch(rcp);
diff --git a/kernel/rcupreempt.c b/kernel/rcupreempt.c
index 04982659875a..f9dc8f3720f6 100644
--- a/kernel/rcupreempt.c
+++ b/kernel/rcupreempt.c
@@ -164,7 +164,8 @@ static char *rcu_try_flip_state_names[] =
         { "idle", "waitack", "waitzero", "waitmb" };
 #endif /* #ifdef CONFIG_RCU_TRACE */
 
-static cpumask_t rcu_cpu_online_map __read_mostly = CPU_MASK_NONE;
+static DECLARE_BITMAP(rcu_cpu_online_map, NR_CPUS) __read_mostly
+        = CPU_BITS_NONE;
 
 /*
  * Enum and per-CPU flag to determine when each CPU has seen
@@ -758,7 +759,7 @@ rcu_try_flip_idle(void)
 
         /* Now ask each CPU for acknowledgement of the flip. */
 
-        for_each_cpu_mask_nr(cpu, rcu_cpu_online_map) {
+        for_each_cpu(cpu, to_cpumask(rcu_cpu_online_map)) {
                 per_cpu(rcu_flip_flag, cpu) = rcu_flipped;
                 dyntick_save_progress_counter(cpu);
         }
@@ -776,7 +777,7 @@ rcu_try_flip_waitack(void)
         int cpu;
 
         RCU_TRACE_ME(rcupreempt_trace_try_flip_a1);
-        for_each_cpu_mask_nr(cpu, rcu_cpu_online_map)
+        for_each_cpu(cpu, to_cpumask(rcu_cpu_online_map))
                 if (rcu_try_flip_waitack_needed(cpu) &&
                     per_cpu(rcu_flip_flag, cpu) != rcu_flip_seen) {
                         RCU_TRACE_ME(rcupreempt_trace_try_flip_ae1);
@@ -808,7 +809,7 @@ rcu_try_flip_waitzero(void)
         /* Check to see if the sum of the "last" counters is zero. */
 
         RCU_TRACE_ME(rcupreempt_trace_try_flip_z1);
-        for_each_cpu_mask_nr(cpu, rcu_cpu_online_map)
+        for_each_cpu(cpu, to_cpumask(rcu_cpu_online_map))
                 sum += RCU_DATA_CPU(cpu)->rcu_flipctr[lastidx];
         if (sum != 0) {
                 RCU_TRACE_ME(rcupreempt_trace_try_flip_ze1);
@@ -823,7 +824,7 @@ rcu_try_flip_waitzero(void)
         smp_mb();  /*  ^^^^^^^^^^^^ */
 
         /* Call for a memory barrier from each CPU. */
-        for_each_cpu_mask_nr(cpu, rcu_cpu_online_map) {
+        for_each_cpu(cpu, to_cpumask(rcu_cpu_online_map)) {
                 per_cpu(rcu_mb_flag, cpu) = rcu_mb_needed;
                 dyntick_save_progress_counter(cpu);
         }
@@ -843,7 +844,7 @@ rcu_try_flip_waitmb(void)
         int cpu;
 
         RCU_TRACE_ME(rcupreempt_trace_try_flip_m1);
-        for_each_cpu_mask_nr(cpu, rcu_cpu_online_map)
+        for_each_cpu(cpu, to_cpumask(rcu_cpu_online_map))
                 if (rcu_try_flip_waitmb_needed(cpu) &&