rcutorture: Test SRCU cleanup code path

The current rcutorture testing does not do any cleanup operations.
This works because the srcu_struct is statically allocated, but it
does represent a memory leak of the associated dynamically allocated
->per_cpu_ref per-CPU variables.  However, rcutorture currently uses
a statically allocated srcu_struct, which cannot legally be passed to
cleanup_srcu_struct().  Therefore, this commit adds a second form
of srcu (called srcud) that dynamically allocates and frees the
associated per-CPU variables.  This commit also adds a ->cleanup()
member to rcu_torture_ops that is invoked at the end of the test,
after ->cb_barriers().  This ->cleanup() pointer is NULL for all
existing tests, and thus only used for scrud.  Finally, the SRCU-P
torture-test configuration selects scrud instead of srcu, with SRCU-N
continuing to use srcu, thereby testing both static and dynamic
srcu_struct structures.

Reported-by: "Ahmed, Iftekhar" <ahmedi@onid.oregonstate.edu>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

2 files changed, 59 insertions, 20 deletions

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 90ff8dfc51e5..59e32684c23b 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -241,6 +241,7 @@ rcu_torture_free(struct rcu_torture *p)
 struct rcu_torture_ops {
         int ttype;
         void (*init)(void);
+        void (*cleanup)(void);
         int (*readlock)(void);
         void (*read_delay)(struct torture_random_state *rrsp);
         void (*readunlock)(int idx);
@@ -477,10 +478,12 @@ static struct rcu_torture_ops rcu_busted_ops = {
  */
 
 DEFINE_STATIC_SRCU(srcu_ctl);
+static struct srcu_struct srcu_ctld;
+static struct srcu_struct *srcu_ctlp = &srcu_ctl;
 
-static int srcu_torture_read_lock(void) __acquires(&srcu_ctl)
+static int srcu_torture_read_lock(void) __acquires(srcu_ctlp)
 {
-        return srcu_read_lock(&srcu_ctl);
+        return srcu_read_lock(srcu_ctlp);
 }
 
 static void srcu_read_delay(struct torture_random_state *rrsp)
@@ -499,49 +502,49 @@ static void srcu_read_delay(struct torture_random_state *rrsp)
                 rcu_read_delay(rrsp);
 }
 
-static void srcu_torture_read_unlock(int idx) __releases(&srcu_ctl)
+static void srcu_torture_read_unlock(int idx) __releases(srcu_ctlp)
 {
-        srcu_read_unlock(&srcu_ctl, idx);
+        srcu_read_unlock(srcu_ctlp, idx);
 }
 
 static unsigned long srcu_torture_completed(void)
 {
-        return srcu_batches_completed(&srcu_ctl);
+        return srcu_batches_completed(srcu_ctlp);
 }
 
 static void srcu_torture_deferred_free(struct rcu_torture *rp)
 {
-        call_srcu(&srcu_ctl, &rp->rtort_rcu, rcu_torture_cb);
+        call_srcu(srcu_ctlp, &rp->rtort_rcu, rcu_torture_cb);
 }
 
 static void srcu_torture_synchronize(void)
 {
-        synchronize_srcu(&srcu_ctl);
+        synchronize_srcu(srcu_ctlp);
 }
 
 static void srcu_torture_call(struct rcu_head *head,
                               void (*func)(struct rcu_head *head))
 {
-        call_srcu(&srcu_ctl, head, func);
+        call_srcu(srcu_ctlp, head, func);
 }
 
 static void srcu_torture_barrier(void)
 {
-        srcu_barrier(&srcu_ctl);
+        srcu_barrier(srcu_ctlp);
 }
 
 static void srcu_torture_stats(void)
 {
         int cpu;
-        int idx = srcu_ctl.completed & 0x1;
+        int idx = srcu_ctlp->completed & 0x1;
 
         pr_alert("%s%s per-CPU(idx=%d):",
                  torture_type, TORTURE_FLAG, idx);
         for_each_possible_cpu(cpu) {
                 long c0, c1;
 
-                c0 = (long)per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx];
-                c1 = (long)per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx];
+                c0 = (long)per_cpu_ptr(srcu_ctlp->per_cpu_ref, cpu)->c[!idx];
+                c1 = (long)per_cpu_ptr(srcu_ctlp->per_cpu_ref, cpu)->c[idx];
                 pr_cont(" %d(%ld,%ld)", cpu, c0, c1);
         }
         pr_cont("\n");
@@ -549,7 +552,7 @@ static void srcu_torture_stats(void)
 
 static void srcu_torture_synchronize_expedited(void)
 {
-        synchronize_srcu_expedited(&srcu_ctl);
+        synchronize_srcu_expedited(srcu_ctlp);
 }
 
 static struct rcu_torture_ops srcu_ops = {
@@ -569,6 +572,38 @@ static struct rcu_torture_ops srcu_ops = {
         .name           = "srcu"
 };
 
+static void srcu_torture_init(void)
+{
+        rcu_sync_torture_init();
+        WARN_ON(init_srcu_struct(&srcu_ctld));
+        srcu_ctlp = &srcu_ctld;
+}
+
+static void srcu_torture_cleanup(void)
+{
+        cleanup_srcu_struct(&srcu_ctld);
+        srcu_ctlp = &srcu_ctl; /* In case of a later rcutorture run. */
+}
+
+/* As above, but dynamically allocated. */
+static struct rcu_torture_ops srcud_ops = {
+        .ttype          = SRCU_FLAVOR,
+        .init           = srcu_torture_init,
+        .cleanup        = srcu_torture_cleanup,
+        .readlock       = srcu_torture_read_lock,
+        .read_delay     = srcu_read_delay,
+        .readunlock     = srcu_torture_read_unlock,
+        .started        = NULL,
+        .completed      = srcu_torture_completed,
+        .deferred_free  = srcu_torture_deferred_free,
+        .sync           = srcu_torture_synchronize,
+        .exp_sync       = srcu_torture_synchronize_expedited,
+        .call           = srcu_torture_call,
+        .cb_barrier     = srcu_torture_barrier,
+        .stats          = srcu_torture_stats,
+        .name           = "srcud"
+};
+
 /*
  * Definitions for sched torture testing.
  */
@@ -1053,7 +1088,7 @@ static void rcu_torture_timer(unsigned long unused)
         p = rcu_dereference_check(rcu_torture_current,
                                   rcu_read_lock_bh_held() ||
                                   rcu_read_lock_sched_held() ||
-                                  srcu_read_lock_held(&srcu_ctl));
+                                  srcu_read_lock_held(srcu_ctlp));
         if (p == NULL) {
                 /* Leave because rcu_torture_writer is not yet underway */
                 cur_ops->readunlock(idx);
@@ -1127,7 +1162,7 @@ rcu_torture_reader(void *arg)
                 p = rcu_dereference_check(rcu_torture_current,
                                           rcu_read_lock_bh_held() ||
                                           rcu_read_lock_sched_held() ||
-                                          srcu_read_lock_held(&srcu_ctl));
+                                          srcu_read_lock_held(srcu_ctlp));
                 if (p == NULL) {
                         /* Wait for rcu_torture_writer to get underway */
                         cur_ops->readunlock(idx);
@@ -1590,10 +1625,14 @@ rcu_torture_cleanup(void)
                         rcutorture_booster_cleanup(i);
         }
 
-        /* Wait for all RCU callbacks to fire.  */
-
+        /*
+         * Wait for all RCU callbacks to fire, then do flavor-specific
+         * cleanup operations.
+         */
         if (cur_ops->cb_barrier != NULL)
                 cur_ops->cb_barrier();
+        if (cur_ops->cleanup != NULL)
+                cur_ops->cleanup();
 
         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
 
@@ -1670,8 +1709,8 @@ rcu_torture_init(void)
         int cpu;
         int firsterr = 0;
         static struct rcu_torture_ops *torture_ops[] = {
-                &rcu_ops, &rcu_bh_ops, &rcu_busted_ops, &srcu_ops, &sched_ops,
-                RCUTORTURE_TASKS_OPS
+                &rcu_ops, &rcu_bh_ops, &rcu_busted_ops, &srcu_ops, &srcud_ops,
+                &sched_ops, RCUTORTURE_TASKS_OPS
         };
 
         if (!torture_init_begin(torture_type, verbose, &torture_runnable))
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/SRCU-P.boot b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-P.boot
index 238bfe3bd0cc..84a7d51b7481 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/SRCU-P.boot
+++ b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-P.boot
@@ -1 +1 @@
-rcutorture.torture_type=srcu
+rcutorture.torture_type=srcud