Commit 2f084695 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Mark rcu_state.ncpus to detect concurrent writes 



The rcu_state structure's ncpus field is only to be modified by the
CPU-hotplug CPU-online code path, 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 4f58820f

kernel/rcu/tree.c

+1 −0
Original line number Diff line number Diff line
@@ -3612,6 +3612,7 @@ void rcu_cpu_starting(unsigned int cpu) 
	nbits = bitmap_weight(&oldmask, BITS_PER_LONG);

	/* Allow lockless access for expedited grace periods. */

	smp_store_release(&rcu_state.ncpus, rcu_state.ncpus + nbits); /* ^^^ */

	ASSERT_EXCLUSIVE_WRITER(rcu_state.ncpus);

	rcu_gpnum_ovf(rnp, rdp); /* Offline-induced counter wrap? */

	rdp->rcu_onl_gp_seq = READ_ONCE(rcu_state.gp_seq);

	rdp->rcu_onl_gp_flags = READ_ONCE(rcu_state.gp_flags);