Merge branch 'akpm'

* akpm:
  kernel/smp.c: consolidate writes in smp_call_function_interrupt()
  kernel/smp.c: fix smp_call_function_many() SMP race
  memcg: correctly order reading PCG_USED and pc->mem_cgroup
  backlight: fix 88pm860x_bl macro collision
  drivers/leds/ledtrig-gpio.c: make output match input, tighten input checking
  MAINTAINERS: update Atmel AT91 entry
  mm: fix truncate_setsize() comment
  memcg: fix rmdir, force_empty with THP
  memcg: fix LRU accounting with THP
  memcg: fix USED bit handling at uncharge in THP
  memcg: modify accounting function for supporting THP better
  fs/direct-io.c: don't try to allocate more than BIO_MAX_PAGES in a bio
  mm: compaction: prevent division-by-zero during user-requested compaction
  mm/vmscan.c: remove duplicate include of compaction.h
  memblock: fix memblock_is_region_memory()
  thp: keep highpte mapped until it is no longer needed
  kconfig: rename CONFIG_EMBEDDED to CONFIG_EXPERT

1 files changed, 45 insertions, 6 deletions

diff --git a/kernel/smp.c b/kernel/smp.c
index 4ec30e06998..2fe66f7c617 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -194,23 +194,52 @@ void generic_smp_call_function_interrupt(void)
          */
         list_for_each_entry_rcu(data, &call_function.queue, csd.list) {
                 int refs;
+                void (*func) (void *info);
 
-                if (!cpumask_test_and_clear_cpu(cpu, data->cpumask))
+                /*
+                 * Since we walk the list without any locks, we might
+                 * see an entry that was completed, removed from the
+                 * list and is in the process of being reused.
+                 *
+                 * We must check that the cpu is in the cpumask before
+                 * checking the refs, and both must be set before
+                 * executing the callback on this cpu.
+                 */
+
+                if (!cpumask_test_cpu(cpu, data->cpumask))
                         continue;
 
+                smp_rmb();
+
+                if (atomic_read(&data->refs) == 0)
+                        continue;
+
+                func = data->csd.func;                  /* for later warn */
                 data->csd.func(data->csd.info);
 
+                /*
+                 * If the cpu mask is not still set then it enabled interrupts,
+                 * we took another smp interrupt, and executed the function
+                 * twice on this cpu.  In theory that copy decremented refs.
+                 */
+                if (!cpumask_test_and_clear_cpu(cpu, data->cpumask)) {
+                        WARN(1, "%pS enabled interrupts and double executed\n",
+                             func);
+                        continue;
+                }
+
                 refs = atomic_dec_return(&data->refs);
                 WARN_ON(refs < 0);
-                if (!refs) {
-                        raw_spin_lock(&call_function.lock);
-                        list_del_rcu(&data->csd.list);
-                        raw_spin_unlock(&call_function.lock);
-                }
 
                 if (refs)
                         continue;
 
+                WARN_ON(!cpumask_empty(data->cpumask));
+
+                raw_spin_lock(&call_function.lock);
+                list_del_rcu(&data->csd.list);
+                raw_spin_unlock(&call_function.lock);
+
                 csd_unlock(&data->csd);
         }
 
@@ -454,11 +483,21 @@ void smp_call_function_many(const struct cpumask *mask,
 
         data = &__get_cpu_var(cfd_data);
         csd_lock(&data->csd);
+        BUG_ON(atomic_read(&data->refs) || !cpumask_empty(data->cpumask));
 
         data->csd.func = func;
         data->csd.info = info;
         cpumask_and(data->cpumask, mask, cpu_online_mask);
         cpumask_clear_cpu(this_cpu, data->cpumask);
+
+        /*
+         * To ensure the interrupt handler gets an complete view
+         * we order the cpumask and refs writes and order the read
+         * of them in the interrupt handler.  In addition we may
+         * only clear our own cpu bit from the mask.
+         */
+        smp_wmb();
+
         atomic_set(&data->refs, cpumask_weight(data->cpumask));
 
         raw_spin_lock_irqsave(&call_function.lock, flags);