Commit ae3c0706 authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Paul E. McKenney
Browse files

srcu: Explain the reason behind the read side critical section on GP start 



Tell about the need to protect against concurrent updaters who may
overflow the GP counter behind the current update.

Reported-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Signed-off-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 6b77bb9b

kernel/rcu/srcutree.c

+5 −0
Original line number Diff line number Diff line
@@ -1158,6 +1158,11 @@ static unsigned long srcu_gp_start_if_needed(struct srcu_struct *ssp, 
	int ss_state;



	check_init_srcu_struct(ssp);

	/*

	 * While starting a new grace period, make sure we are in an

	 * SRCU read-side critical section so that the grace-period

	 * sequence number cannot wrap around in the meantime.

	 */

	idx = __srcu_read_lock_nmisafe(ssp, false);

	ss_state = smp_load_acquire(&ssp->srcu_size_state);

	if (ss_state < SRCU_SIZE_WAIT_CALL)