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authorPaul E. McKenney <paulmck@kernel.org>2022-02-04 23:45:18 +0300
committerPaul E. McKenney <paulmck@kernel.org>2022-04-12 03:07:28 +0300
commit99d6a2acb8955f12489bfba04f2db22bc0b57726 (patch)
tree8406975fc059e6fe639ecd16465658bdd6a97bbf /kernel/rcu
parentb6f3c6a2b1fe2d754acb7bf64a20e64a8f2c8a1b (diff)
downloadlinux-99d6a2acb8955f12489bfba04f2db22bc0b57726.tar.xz
rcutorture: Suppress debugging grace period delays during flooding
Tree RCU supports grace-period delays using the rcutree.gp_cleanup_delay, rcutree.gp_init_delay, and rcutree.gp_preinit_delay kernel boot parameters. These delays are strictly for debugging purposes, and have proven quite effective at exposing bugs involving race with CPU-hotplug operations. However, these delays can result in false positives when used in conjunction with callback flooding, for example, those generated by the rcutorture.fwd_progress kernel boot parameter. This commit therefore suppresses grace-period delays while callback flooding is in progress. Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu')
-rw-r--r--kernel/rcu/rcu.h4
-rw-r--r--kernel/rcu/rcutorture.c4
-rw-r--r--kernel/rcu/tree.c32
3 files changed, 37 insertions, 3 deletions
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index 24b5f2c2de87..7a221393fcdb 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -523,6 +523,8 @@ static inline bool rcu_check_boost_fail(unsigned long gp_state, int *cpup) { ret
static inline void show_rcu_gp_kthreads(void) { }
static inline int rcu_get_gp_kthreads_prio(void) { return 0; }
static inline void rcu_fwd_progress_check(unsigned long j) { }
+static inline void rcu_gp_slow_register(atomic_t *rgssp) { }
+static inline void rcu_gp_slow_unregister(atomic_t *rgssp) { }
#else /* #ifdef CONFIG_TINY_RCU */
bool rcu_dynticks_zero_in_eqs(int cpu, int *vp);
unsigned long rcu_get_gp_seq(void);
@@ -535,6 +537,8 @@ void rcu_fwd_progress_check(unsigned long j);
void rcu_force_quiescent_state(void);
extern struct workqueue_struct *rcu_gp_wq;
extern struct workqueue_struct *rcu_par_gp_wq;
+void rcu_gp_slow_register(atomic_t *rgssp);
+void rcu_gp_slow_unregister(atomic_t *rgssp);
#endif /* #else #ifdef CONFIG_TINY_RCU */
#ifdef CONFIG_RCU_NOCB_CPU
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 55d049c39608..f37b7a01dcd0 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -2916,10 +2916,12 @@ rcu_torture_cleanup(void)
pr_info("%s: Invoking %pS().\n", __func__, cur_ops->cb_barrier);
cur_ops->cb_barrier();
}
+ rcu_gp_slow_unregister(NULL);
return;
}
if (!cur_ops) {
torture_cleanup_end();
+ rcu_gp_slow_unregister(NULL);
return;
}
@@ -3016,6 +3018,7 @@ rcu_torture_cleanup(void)
else
rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS");
torture_cleanup_end();
+ rcu_gp_slow_unregister(&rcu_fwd_cb_nodelay);
}
#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
@@ -3320,6 +3323,7 @@ rcu_torture_init(void)
if (object_debug)
rcu_test_debug_objects();
torture_init_end();
+ rcu_gp_slow_register(&rcu_fwd_cb_nodelay);
return 0;
unwind:
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index a4b8189455d5..db67dae8ed88 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1705,11 +1705,37 @@ static void note_gp_changes(struct rcu_data *rdp)
rcu_gp_kthread_wake();
}
+static atomic_t *rcu_gp_slow_suppress;
+
+/* Register a counter to suppress debugging grace-period delays. */
+void rcu_gp_slow_register(atomic_t *rgssp)
+{
+ WARN_ON_ONCE(rcu_gp_slow_suppress);
+
+ WRITE_ONCE(rcu_gp_slow_suppress, rgssp);
+}
+EXPORT_SYMBOL_GPL(rcu_gp_slow_register);
+
+/* Unregister a counter, with NULL for not caring which. */
+void rcu_gp_slow_unregister(atomic_t *rgssp)
+{
+ WARN_ON_ONCE(rgssp && rgssp != rcu_gp_slow_suppress);
+
+ WRITE_ONCE(rcu_gp_slow_suppress, NULL);
+}
+EXPORT_SYMBOL_GPL(rcu_gp_slow_unregister);
+
+static bool rcu_gp_slow_is_suppressed(void)
+{
+ atomic_t *rgssp = READ_ONCE(rcu_gp_slow_suppress);
+
+ return rgssp && atomic_read(rgssp);
+}
+
static void rcu_gp_slow(int delay)
{
- if (delay > 0 &&
- !(rcu_seq_ctr(rcu_state.gp_seq) %
- (rcu_num_nodes * PER_RCU_NODE_PERIOD * delay)))
+ if (!rcu_gp_slow_is_suppressed() && delay > 0 &&
+ !(rcu_seq_ctr(rcu_state.gp_seq) % (rcu_num_nodes * PER_RCU_NODE_PERIOD * delay)))
schedule_timeout_idle(delay);
}