rcu: Mark rcu_state.ncpus to detect concurrent writes (2f084695) · Commits · 戴 / test

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:

Paul E. McKenney <paulmck@kernel.org>

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);

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