Commit 9ff86b4c authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu-tasks: Make trc_read_check_handler() fetch ->trc_reader_nesting only once 



This commit replaces the pair of READ_ONCE(t->trc_reader_nesting) calls
with a single such call and a local variable.  This makes the code's
intent more clear.

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: KP Singh <kpsingh@kernel.org>
parent 55061126

kernel/rcu/tasks.h

+4 −2
Original line number Diff line number Diff line
@@ -1278,6 +1278,7 @@ static void trc_del_holdout(struct task_struct *t) 
/* IPI handler to check task state. */

static void trc_read_check_handler(void *t_in)

{

	int nesting;

	struct task_struct *t = current;

	struct task_struct *texp = t_in;
@@ -1287,12 +1288,13 @@ static void trc_read_check_handler(void *t_in) 


	// If the task is not in a read-side critical section, and

	// if this is the last reader, awaken the grace-period kthread.

	if (likely(!READ_ONCE(t->trc_reader_nesting))) {

	nesting = READ_ONCE(t->trc_reader_nesting);

	if (likely(!nesting)) {

		rcu_trc_cmpxchg_need_qs(t, 0, TRC_NEED_QS_CHECKED);

		goto reset_ipi;

	}

	// If we are racing with an rcu_read_unlock_trace(), try again later.

	if (unlikely(READ_ONCE(t->trc_reader_nesting) < 0))

	if (unlikely(nesting < 0))

		goto reset_ipi;



	// Get here if the task is in a read-side critical section.  Set