Commit 62ae1951 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Mark rcu_state.gp_seq to detect more concurrent writes 



The rcu_state structure's gp_seq field is only to be modified by the RCU
grace-period kthread, which is single-threaded.  This commit therefore
enlists KCSAN's help in enforcing this restriction.  This commit applies
KCSAN-specific primitives, so cannot go upstream until KCSAN does.

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent c28d5c09

kernel/rcu/tree.c

+3 −1
Original line number Diff line number Diff line
@@ -1230,7 +1230,7 @@ static bool rcu_start_this_gp(struct rcu_node *rnp_start, struct rcu_data *rdp, 
		trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("NoGPkthread"));

		goto unlock_out;

	}

	trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("newreq"));

	trace_rcu_grace_period(rcu_state.name, data_race(rcu_state.gp_seq), TPS("newreq"));

	ret = true;  /* Caller must wake GP kthread. */

unlock_out:

	/* Push furthest requested GP to leaf node and rcu_data structure. */
@@ -1519,6 +1519,7 @@ static bool rcu_gp_init(void) 
	record_gp_stall_check_time();

	/* Record GP times before starting GP, hence rcu_seq_start(). */

	rcu_seq_start(&rcu_state.gp_seq);

	ASSERT_EXCLUSIVE_WRITER(rcu_state.gp_seq);

	trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("start"));

	raw_spin_unlock_irq_rcu_node(rnp);
@@ -1805,6 +1806,7 @@ static void rcu_gp_cleanup(void) 
	/* Declare grace period done, trace first to use old GP number. */

	trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("end"));

	rcu_seq_end(&rcu_state.gp_seq);

	ASSERT_EXCLUSIVE_WRITER(rcu_state.gp_seq);

	rcu_state.gp_state = RCU_GP_IDLE;

	/* Check for GP requests since above loop. */

	rdp = this_cpu_ptr(&rcu_data);