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rcu-tasks: Add count for idle tasks on offline CPUs
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This commit adds a counter for the number of times the quiescent state
was an idle task associated with an offline CPU, and prints this count
at the end of rcutorture runs and at stall time.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Paul E. McKenney committed Apr 27, 2020
1 parent 4047150 commit edf3775
Showing 1 changed file with 5 additions and 1 deletion.
6 changes: 5 additions & 1 deletion kernel/rcu/tasks.h
Original file line number Diff line number Diff line change
Expand Up @@ -729,6 +729,7 @@ static DEFINE_PER_CPU(bool, trc_ipi_to_cpu);
// heavyweight readers executing explicit memory barriers.
unsigned long n_heavy_reader_attempts;
unsigned long n_heavy_reader_updates;
unsigned long n_heavy_reader_ofl_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,
Expand Down Expand Up @@ -840,6 +841,8 @@ static bool trc_inspect_reader(struct task_struct *t, void *arg)
!rcu_dynticks_zero_in_eqs(cpu, &t->trc_reader_nesting))
return false; // No quiescent state, do it the hard way.
n_heavy_reader_updates++;
if (ofl)
n_heavy_reader_ofl_updates++;
in_qs = true;
} else {
in_qs = likely(!t->trc_reader_nesting);
Expand Down Expand Up @@ -1156,7 +1159,8 @@ static void show_rcu_tasks_trace_gp_kthread(void)
{
char buf[64];

sprintf(buf, "N%d h:%lu/%lu", atomic_read(&trc_n_readers_need_end),
sprintf(buf, "N%d h:%lu/%lu/%lu", atomic_read(&trc_n_readers_need_end),
data_race(n_heavy_reader_ofl_updates),
data_race(n_heavy_reader_updates),
data_race(n_heavy_reader_attempts));
show_rcu_tasks_generic_gp_kthread(&rcu_tasks_trace, buf);
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