Vanilla RCU readers, when either non-preemptible or preemptible with priority-boosting enabled, can handle heavy overload conditions. Other RCU implementations are more fragile. This commit adds an rcu_torture_ops structure field named ->rdrs_handle_load that is set for non-fragile configurations of vanilla RCU, but cleared otherwise. It also refrains from running fragile readers concurrently with overload testing, thus avoiding false-positive overload-testing failures.
Signed-off-by: Paul E. McKenney <[email protected]> --- kernel/rcu/rcutorture.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 794937e13e7c..7e08be857f01 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -440,6 +440,7 @@ struct rcu_torture_ops { int debug_objects; int start_poll_irqsoff; int have_up_down; + int rdrs_handle_load; const char *name; }; @@ -648,6 +649,7 @@ static struct rcu_torture_ops rcu_ops = { .extendables = RCUTORTURE_MAX_EXTEND, .debug_objects = 1, .start_poll_irqsoff = 1, + .rdrs_handle_load = !IS_ENABLED(CONFIG_PREEMPT_RCU) || IS_ENABLED(CONFIG_RCU_BOOST), .name = "rcu" }; @@ -2534,8 +2536,10 @@ static bool rcu_torture_one_read_start(struct rcu_torture_one_read_state *rtorsp rtorsp->p = rcu_dereference_check(rcu_torture_current, !cur_ops->readlock_held || cur_ops->readlock_held() || (rtorsp->readstate & RCUTORTURE_RDR_UPDOWN)); - if (rtorsp->p == NULL) { - /* Wait for rcu_torture_writer to get underway */ + if ((!cur_ops->rdrs_handle_load && atomic_read(&rcu_fwd_cb_nodelay)) || rtorsp->p == NULL) { + // Wait for rcu_torture_writer to get underway and + // (if readers cannot handle heavy loads) for any + // forward-progress testing to complete. rcutorture_one_extend(&rtorsp->readstate, 0, trsp, rtorsp->rtrsp); return false; } -- 2.40.1
