From: "Paul E. McKenney" paulmck@kernel.org
[ Upstream commit f8ab3fad80dddf3f2cecb53983063c4431058ca1 ]
There are several ->trc_reader_special.b.need_qs data races that are too low-probability for KCSAN to notice, but which will happen sooner or later. This commit therefore marks these accesses.
Cc: stable@vger.kernel.org # 5.10.x Signed-off-by: Paul E. McKenney paulmck@kernel.org Signed-off-by: Joel Fernandes (Google) joel@joelfernandes.org --- kernel/rcu/tasks.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 2b16a86163af..aef2e96c3854 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -801,7 +801,7 @@ static DEFINE_IRQ_WORK(rcu_tasks_trace_iw, rcu_read_unlock_iw); /* If we are the last reader, wake up the grace-period kthread. */ void rcu_read_unlock_trace_special(struct task_struct *t, int nesting) { - int nq = t->trc_reader_special.b.need_qs; + int nq = READ_ONCE(t->trc_reader_special.b.need_qs);
if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB) && t->trc_reader_special.b.need_mb) @@ -867,7 +867,7 @@ static void trc_read_check_handler(void *t_in) // Get here if the task is in a read-side critical section. Set // its state so that it will awaken the grace-period kthread upon // exit from that critical section. - WARN_ON_ONCE(t->trc_reader_special.b.need_qs); + WARN_ON_ONCE(READ_ONCE(t->trc_reader_special.b.need_qs)); WRITE_ONCE(t->trc_reader_special.b.need_qs, true);
reset_ipi: @@ -919,7 +919,7 @@ static bool trc_inspect_reader(struct task_struct *t, void *arg) // state so that it will awaken the grace-period kthread upon exit // from that critical section. atomic_inc(&trc_n_readers_need_end); // One more to wait on. - WARN_ON_ONCE(t->trc_reader_special.b.need_qs); + WARN_ON_ONCE(READ_ONCE(t->trc_reader_special.b.need_qs)); WRITE_ONCE(t->trc_reader_special.b.need_qs, true); return true; } @@ -1048,7 +1048,7 @@ static void show_stalled_task_trace(struct task_struct *t, bool *firstreport) ".i"[is_idle_task(t)], ".N"[cpu > 0 && tick_nohz_full_cpu(cpu)], READ_ONCE(t->trc_reader_nesting), - " N"[!!t->trc_reader_special.b.need_qs], + " N"[!!READ_ONCE(t->trc_reader_special.b.need_qs)], cpu); sched_show_task(t); }