rcu/tasks-trace: Handle new PF_IDLE semantics

[ Upstream commit a80712b9cc7e57830260ec5e1feb9cdb59e1da2f ]

The commit:

	cff9b2332ab7 ("kernel/sched: Modify initial boot task idle setup")

has changed the semantics of what is to be considered an idle task in
such a way that the idle task of an offline CPU may not carry the
PF_IDLE flag anymore.

However RCU-tasks-trace tests the opposite assertion, still assuming
that idle tasks carry the PF_IDLE flag during their whole lifecycle.

Remove this assumption to avoid spurious warnings but keep the initial
test verifying that the idle task is the current task on any offline
CPU.

Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Fixes: cff9b2332ab7 ("kernel/sched: Modify initial boot task idle setup")
Suggested-by: Joel Fernandes <joel@joelfernandes.org>
Suggested-by: "Paul E. McKenney" <paulmck@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index b5dc1e5..65e000c 100644 (file)
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1548,7 +1548,7 @@ static int trc_inspect_reader(struct task_struct *t, void *bhp_in)
        } else {
                // The task is not running, so C-language access is safe.
                nesting = t->trc_reader_nesting;
-               WARN_ON_ONCE(ofl && task_curr(t) && !is_idle_task(t));
+               WARN_ON_ONCE(ofl && task_curr(t) && (t != idle_task(task_cpu(t))));
                if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB) && ofl)
                        n_heavy_reader_ofl_updates++;
        }