Commit 0f11ad32 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Mark rcu_state.gp_seq to detect 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.

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 3d05031a

kernel/rcu/tree.c

+8 −14
Original line number Diff line number Diff line
@@ -1209,7 +1209,7 @@ 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, READ_ONCE(rcu_state.gp_seq), TPS("newreq"));

	trace_rcu_grace_period(rcu_state.name, 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. */
@@ -1657,8 +1657,7 @@ static void rcu_gp_fqs_loop(void) 
			WRITE_ONCE(rcu_state.jiffies_kick_kthreads,

				   jiffies + (j ? 3 * j : 2));

		}

		trace_rcu_grace_period(rcu_state.name,

				       READ_ONCE(rcu_state.gp_seq),

		trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,

				       TPS("fqswait"));

		rcu_state.gp_state = RCU_GP_WAIT_FQS;

		ret = swait_event_idle_timeout_exclusive(
@@ -1672,13 +1671,11 @@ static void rcu_gp_fqs_loop(void) 
		/* If time for quiescent-state forcing, do it. */

		if (ULONG_CMP_GE(jiffies, rcu_state.jiffies_force_qs) ||

		    (gf & RCU_GP_FLAG_FQS)) {

			trace_rcu_grace_period(rcu_state.name,

					       READ_ONCE(rcu_state.gp_seq),

			trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,

					       TPS("fqsstart"));

			rcu_gp_fqs(first_gp_fqs);

			first_gp_fqs = false;

			trace_rcu_grace_period(rcu_state.name,

					       READ_ONCE(rcu_state.gp_seq),

			trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,

					       TPS("fqsend"));

			cond_resched_tasks_rcu_qs();

			WRITE_ONCE(rcu_state.gp_activity, jiffies);
@@ -1689,8 +1686,7 @@ static void rcu_gp_fqs_loop(void) 
			cond_resched_tasks_rcu_qs();

			WRITE_ONCE(rcu_state.gp_activity, jiffies);

			WARN_ON(signal_pending(current));

			trace_rcu_grace_period(rcu_state.name,

					       READ_ONCE(rcu_state.gp_seq),

			trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,

					       TPS("fqswaitsig"));

			ret = 1; /* Keep old FQS timing. */

			j = jiffies;
@@ -1782,7 +1778,7 @@ static void rcu_gp_cleanup(void) 
		WRITE_ONCE(rcu_state.gp_flags, RCU_GP_FLAG_INIT);

		WRITE_ONCE(rcu_state.gp_req_activity, jiffies);

		trace_rcu_grace_period(rcu_state.name,

				       READ_ONCE(rcu_state.gp_seq),

				       rcu_state.gp_seq,

				       TPS("newreq"));

	} else {

		WRITE_ONCE(rcu_state.gp_flags,
@@ -1801,8 +1797,7 @@ static int __noreturn rcu_gp_kthread(void *unused) 


		/* Handle grace-period start. */

		for (;;) {

			trace_rcu_grace_period(rcu_state.name,

					       READ_ONCE(rcu_state.gp_seq),

			trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,

					       TPS("reqwait"));

			rcu_state.gp_state = RCU_GP_WAIT_GPS;

			swait_event_idle_exclusive(rcu_state.gp_wq,
@@ -1815,8 +1810,7 @@ static int __noreturn rcu_gp_kthread(void *unused) 
			cond_resched_tasks_rcu_qs();

			WRITE_ONCE(rcu_state.gp_activity, jiffies);

			WARN_ON(signal_pending(current));

			trace_rcu_grace_period(rcu_state.name,

					       READ_ONCE(rcu_state.gp_seq),

			trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,

					       TPS("reqwaitsig"));

		}