Commit 40471509 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

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: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 9796e1ae

kernel/rcu/tasks.h

+11 −2
Original line number Diff line number Diff line
@@ -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);

}