sched/dl: Use dl_bw_of() under rcu_read_lock_sched()

rq->rd is freed using call_rcu_sched(), so rcu_read_lock() to access it
is not enough. We should use either rcu_read_lock_sched() or preempt_disable().

Reported-by: Sasha Levin <sasha.levin@oracle.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kirill Tkhai <ktkhai@parallels.com
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Fixes: 66339c31bc39 "sched: Use dl_bw_of() under RCU read lock"
Link: http://lkml.kernel.org/r/1412065417.20287.24.camel@tkhai
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 16 insertions, 9 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b5349fee1213..c84bdc098656 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5264,6 +5264,7 @@ static int sched_cpu_inactive(struct notifier_block *nfb,
 {
         unsigned long flags;
         long cpu = (long)hcpu;
+        struct dl_bw *dl_b;
 
         switch (action & ~CPU_TASKS_FROZEN) {
         case CPU_DOWN_PREPARE:
@@ -5271,15 +5272,19 @@ static int sched_cpu_inactive(struct notifier_block *nfb,
 
                 /* explicitly allow suspend */
                 if (!(action & CPU_TASKS_FROZEN)) {
-                        struct dl_bw *dl_b = dl_bw_of(cpu);
                         bool overflow;
                         int cpus;
 
+                        rcu_read_lock_sched();
+                        dl_b = dl_bw_of(cpu);
+
                         raw_spin_lock_irqsave(&dl_b->lock, flags);
                         cpus = dl_bw_cpus(cpu);
                         overflow = __dl_overflow(dl_b, cpus, 0, 0);
                         raw_spin_unlock_irqrestore(&dl_b->lock, flags);
 
+                        rcu_read_unlock_sched();
+
                         if (overflow)
                                 return notifier_from_errno(-EBUSY);
                 }
@@ -7647,11 +7652,10 @@ static int sched_dl_global_constraints(void)
         u64 runtime = global_rt_runtime();
         u64 period = global_rt_period();
         u64 new_bw = to_ratio(period, runtime);
+        struct dl_bw *dl_b;
         int cpu, ret = 0;
         unsigned long flags;
 
-        rcu_read_lock();
-
         /*
          * Here we want to check the bandwidth not being set to some
          * value smaller than the currently allocated bandwidth in
@@ -7662,25 +7666,27 @@ static int sched_dl_global_constraints(void)
          * solutions is welcome!
          */
         for_each_possible_cpu(cpu) {
-                struct dl_bw *dl_b = dl_bw_of(cpu);
+                rcu_read_lock_sched();
+                dl_b = dl_bw_of(cpu);
 
                 raw_spin_lock_irqsave(&dl_b->lock, flags);
                 if (new_bw < dl_b->total_bw)
                         ret = -EBUSY;
                 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
 
+                rcu_read_unlock_sched();
+
                 if (ret)
                         break;
         }
 
-        rcu_read_unlock();
-
         return ret;
 }
 
 static void sched_dl_do_global(void)
 {
         u64 new_bw = -1;
+        struct dl_bw *dl_b;
         int cpu;
         unsigned long flags;
 
@@ -7690,18 +7696,19 @@ static void sched_dl_do_global(void)
         if (global_rt_runtime() != RUNTIME_INF)
                 new_bw = to_ratio(global_rt_period(), global_rt_runtime());
 
-        rcu_read_lock();
         /*
          * FIXME: As above...
          */
         for_each_possible_cpu(cpu) {
-                struct dl_bw *dl_b = dl_bw_of(cpu);
+                rcu_read_lock_sched();
+                dl_b = dl_bw_of(cpu);
 
                 raw_spin_lock_irqsave(&dl_b->lock, flags);
                 dl_b->bw = new_bw;
                 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
+
+                rcu_read_unlock_sched();
         }
-        rcu_read_unlock();
 }
 
 static int sched_rt_global_validate(void)