The following commit has been merged into the core/rcu branch of tip: Commit-ID: 40471509be3cb8c9c02aec1c316614cb96e6fe85 Gitweb: https://git.kernel.org/tip/40471509be3cb8c9c02aec1c316614cb96e6fe85 Author: Paul E. McKenney <[email protected]> AuthorDate: Sun, 22 Mar 2020 13:34:34 -07:00 Committer: Paul E. McKenney <[email protected]> CommitterDate: Mon, 27 Apr 2020 11:03:52 -07:00
rcu-tasks: Add rcu_dynticks_zero_in_eqs() effectiveness statistics This commit adds counts of the number of calls and number of successful calls to rcu_dynticks_zero_in_eqs(), which are printed at the end of rcutorture runs and at stall time. This allows evaluation of the effectiveness of rcu_dynticks_zero_in_eqs(). Signed-off-by: Paul E. McKenney <[email protected]> --- kernel/rcu/tasks.h | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index f272e8f..ce65883 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -725,6 +725,11 @@ DECLARE_WAIT_QUEUE_HEAD(trc_wait); // List of holdout tasks. // Record outstanding IPIs to each CPU. No point in sending two... static DEFINE_PER_CPU(bool, trc_ipi_to_cpu); +// The number of detections of task quiescent state relying on +// heavyweight readers executing explicit memory barriers. +unsigned long n_heavy_reader_attempts; +unsigned long n_heavy_reader_updates; + void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func); DEFINE_RCU_TASKS(rcu_tasks_trace, rcu_tasks_wait_gp, call_rcu_tasks_trace, "RCU Tasks Trace"); @@ -830,9 +835,11 @@ static bool trc_inspect_reader(struct task_struct *t, void *arg) // If heavyweight readers are enabled on the remote task, // we can inspect its state despite its currently running. // However, we cannot safely change its state. + n_heavy_reader_attempts++; if (!ofl && // Check for "running" idle tasks on offline CPUs. !rcu_dynticks_zero_in_eqs(cpu, &t->trc_reader_nesting)) return false; // No quiescent state, do it the hard way. + n_heavy_reader_updates++; in_qs = true; } else { in_qs = likely(!t->trc_reader_nesting); @@ -1147,9 +1154,11 @@ core_initcall(rcu_spawn_tasks_trace_kthread); static void show_rcu_tasks_trace_gp_kthread(void) { - char buf[32]; + char buf[64]; - sprintf(buf, "N%d", atomic_read(&trc_n_readers_need_end)); + sprintf(buf, "N%d h:%lu/%lu", atomic_read(&trc_n_readers_need_end), + data_race(n_heavy_reader_updates), + data_race(n_heavy_reader_attempts)); show_rcu_tasks_generic_gp_kthread(&rcu_tasks_trace, buf); }
