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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2014-08-19 08:12:17 +0400
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2014-09-08 03:24:48 +0400
commit38706bc5a29a73645e512c06ffb759fb56259d83 (patch)
tree1bdc7a71e1f1b0b7be46c139c2673bb05dd90cb4 /kernel/rcu
parenteea203fea3484598280a07fe503e025e886297fb (diff)
downloadlinux-38706bc5a29a73645e512c06ffb759fb56259d83.tar.xz
rcutorture: Add callback-flood test
Although RCU is designed to handle arbitrary floods of callbacks, this capability is not routinely tested. This commit therefore adds a cbflood capability in which kthreads repeatedly registers large numbers of callbacks. One such kthread is created for each four CPUs (rounding up), and the test may be controlled by several cbflood_* kernel boot parameters, which control the number of bursts per flood, the number of callbacks per burst, the time between bursts, and the time between floods. The default values are large enough to exercise RCU's emergency responses to callback flooding. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: David Miller <davem@davemloft.net> Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>
Diffstat (limited to 'kernel/rcu')
-rw-r--r--kernel/rcu/rcutorture.c86
1 files changed, 85 insertions, 1 deletions
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index ff4f0c756dee..0bcd53adac73 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -49,11 +49,19 @@
#include <linux/trace_clock.h>
#include <asm/byteorder.h>
#include <linux/torture.h>
+#include <linux/vmalloc.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com> and Josh Triplett <josh@joshtriplett.org>");
+torture_param(int, cbflood_inter_holdoff, HZ,
+ "Holdoff between floods (jiffies)");
+torture_param(int, cbflood_intra_holdoff, 1,
+ "Holdoff between bursts (jiffies)");
+torture_param(int, cbflood_n_burst, 3, "# bursts in flood, zero to disable");
+torture_param(int, cbflood_n_per_burst, 20000,
+ "# callbacks per burst in flood");
torture_param(int, fqs_duration, 0,
"Duration of fqs bursts (us), 0 to disable");
torture_param(int, fqs_holdoff, 0, "Holdoff time within fqs bursts (us)");
@@ -96,10 +104,12 @@ module_param(torture_type, charp, 0444);
MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, rcu_bh, ...)");
static int nrealreaders;
+static int ncbflooders;
static struct task_struct *writer_task;
static struct task_struct **fakewriter_tasks;
static struct task_struct **reader_tasks;
static struct task_struct *stats_task;
+static struct task_struct **cbflood_task;
static struct task_struct *fqs_task;
static struct task_struct *boost_tasks[NR_CPUS];
static struct task_struct *stall_task;
@@ -138,6 +148,7 @@ static long n_rcu_torture_boosts;
static long n_rcu_torture_timers;
static long n_barrier_attempts;
static long n_barrier_successes;
+static atomic_long_t n_cbfloods;
static struct list_head rcu_torture_removed;
static int rcu_torture_writer_state;
@@ -707,6 +718,58 @@ checkwait: stutter_wait("rcu_torture_boost");
return 0;
}
+static void rcu_torture_cbflood_cb(struct rcu_head *rhp)
+{
+}
+
+/*
+ * RCU torture callback-flood kthread. Repeatedly induces bursts of calls
+ * to call_rcu() or analogous, increasing the probability of occurrence
+ * of callback-overflow corner cases.
+ */
+static int
+rcu_torture_cbflood(void *arg)
+{
+ int err = 1;
+ int i;
+ int j;
+ struct rcu_head *rhp;
+
+ if (cbflood_n_per_burst > 0 &&
+ cbflood_inter_holdoff > 0 &&
+ cbflood_intra_holdoff > 0 &&
+ cur_ops->call &&
+ cur_ops->cb_barrier) {
+ rhp = vmalloc(sizeof(*rhp) *
+ cbflood_n_burst * cbflood_n_per_burst);
+ err = !rhp;
+ }
+ if (err) {
+ VERBOSE_TOROUT_STRING("rcu_torture_cbflood disabled: Bad args or OOM");
+ while (!torture_must_stop())
+ schedule_timeout_interruptible(HZ);
+ return 0;
+ }
+ VERBOSE_TOROUT_STRING("rcu_torture_cbflood task started");
+ do {
+ schedule_timeout_interruptible(cbflood_inter_holdoff);
+ atomic_long_inc(&n_cbfloods);
+ WARN_ON(signal_pending(current));
+ for (i = 0; i < cbflood_n_burst; i++) {
+ for (j = 0; j < cbflood_n_per_burst; j++) {
+ cur_ops->call(&rhp[i * cbflood_n_per_burst + j],
+ rcu_torture_cbflood_cb);
+ }
+ schedule_timeout_interruptible(cbflood_intra_holdoff);
+ WARN_ON(signal_pending(current));
+ }
+ cur_ops->cb_barrier();
+ stutter_wait("rcu_torture_cbflood");
+ } while (!torture_must_stop());
+ torture_kthread_stopping("rcu_torture_cbflood");
+ return 0;
+}
+
/*
* RCU torture force-quiescent-state kthread. Repeatedly induces
* bursts of calls to force_quiescent_state(), increasing the probability
@@ -1075,10 +1138,11 @@ rcu_torture_stats_print(void)
n_rcu_torture_boosts,
n_rcu_torture_timers);
torture_onoff_stats();
- pr_cont("barrier: %ld/%ld:%ld\n",
+ pr_cont("barrier: %ld/%ld:%ld ",
n_barrier_successes,
n_barrier_attempts,
n_rcu_torture_barrier_error);
+ pr_cont("cbflood: %ld\n", atomic_long_read(&n_cbfloods));
pr_alert("%s%s ", torture_type, TORTURE_FLAG);
if (atomic_read(&n_rcu_torture_mberror) != 0 ||
@@ -1432,6 +1496,8 @@ rcu_torture_cleanup(void)
torture_stop_kthread(rcu_torture_stats, stats_task);
torture_stop_kthread(rcu_torture_fqs, fqs_task);
+ for (i = 0; i < ncbflooders; i++)
+ torture_stop_kthread(rcu_torture_cbflood, cbflood_task[i]);
if ((test_boost == 1 && cur_ops->can_boost) ||
test_boost == 2) {
unregister_cpu_notifier(&rcutorture_cpu_nb);
@@ -1678,6 +1744,24 @@ rcu_torture_init(void)
goto unwind;
if (object_debug)
rcu_test_debug_objects();
+ if (cbflood_n_burst > 0) {
+ /* Create the cbflood threads */
+ ncbflooders = (num_online_cpus() + 3) / 4;
+ cbflood_task = kcalloc(ncbflooders, sizeof(*cbflood_task),
+ GFP_KERNEL);
+ if (!cbflood_task) {
+ VERBOSE_TOROUT_ERRSTRING("out of memory");
+ firsterr = -ENOMEM;
+ goto unwind;
+ }
+ for (i = 0; i < ncbflooders; i++) {
+ firsterr = torture_create_kthread(rcu_torture_cbflood,
+ NULL,
+ cbflood_task[i]);
+ if (firsterr)
+ goto unwind;
+ }
+ }
rcutorture_record_test_transition();
torture_init_end();
return 0;