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rcutorture: Suppress debugging grace period delays during flooding

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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>
This commit is contained in:
Paul E. McKenney 2022-02-04 12:45:18 -08:00
parent b6f3c6a2b1
commit 99d6a2acb8
3 changed files with 37 additions and 3 deletions
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4
kernel/rcu/rcu.h
View File

@ -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

4
kernel/rcu/rcutorture.c
View File

@ -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:

32
kernel/rcu/tree.c
View File

@ -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);
}