rcutorture: Use per-CPU random state for rcu_torture_timer()

Currently, the rcu_torture_timer() function uses a single global
torture_random_state structure protected by a single global lock.
This conflicts to some extent with performance and scalability,
but even more with the goal of consolidating read-side testing
with rcu_torture_reader().  This commit therefore creates a per-CPU
torture_random_state structure for use by rcu_torture_timer() and
eliminates the lock.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Make rcu_torture_timer_rand static, per 0day Test Robot report. ]

diff --git a/include/linux/torture.h b/include/linux/torture.h
index a55e80817dae01416ef49a4f15582fda52833b23..61dfd93b6ee4d6f47f2609319e01c6192620b3fb 100644 (file)
--- a/include/linux/torture.h
+++ b/include/linux/torture.h
@@ -64,6 +64,8 @@ struct torture_random_state {
        long trs_count;
 };
 #define DEFINE_TORTURE_RANDOM(name) struct torture_random_state name = { 0, 0 }
+#define DEFINE_TORTURE_RANDOM_PERCPU(name) \
+       DEFINE_PER_CPU(struct torture_random_state, name)
 unsigned long torture_random(struct torture_random_state *trsp);
 
 /* Task shuffler, which causes CPUs to occasionally go idle. */

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 2452e4a2992356016d777c9b28f40b8f1cb52ea7..d5a5465d2507dd086af64b5458e83137f9682baa 100644 (file)
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1143,6 +1143,8 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp)
        return true;
 }
 
+static DEFINE_TORTURE_RANDOM_PERCPU(rcu_torture_timer_rand);
+
 /*
  * RCU torture reader from timer handler.  Dereferences rcu_torture_current,
  * incrementing the corresponding element of the pipeline array.  The
@@ -1154,12 +1156,12 @@ static void rcu_torture_timer(struct timer_list *unused)
        int idx;
        unsigned long started;
        unsigned long completed;
-       static DEFINE_TORTURE_RANDOM(rand);
-       static DEFINE_SPINLOCK(rand_lock);
        struct rcu_torture *p;
        int pipe_count;
+       struct torture_random_state *trsp;
        unsigned long long ts;
 
+       trsp = this_cpu_ptr(&rcu_torture_timer_rand);
        atomic_long_inc(&n_rcu_torture_timers);
        idx = cur_ops->readlock();
        started = cur_ops->get_gp_seq();
@@ -1176,9 +1178,7 @@ static void rcu_torture_timer(struct timer_list *unused)
        }
        if (p->rtort_mbtest == 0)
                atomic_inc(&n_rcu_torture_mberror);
-       spin_lock(&rand_lock);
-       cur_ops->read_delay(&rand);
-       spin_unlock(&rand_lock);
+       cur_ops->read_delay(trsp);
        preempt_disable();
        pipe_count = p->rtort_pipe_count;
        if (pipe_count > RCU_TORTURE_PIPE_LEN) {