The following commit has been merged into the core/rcu branch of tip: Commit-ID: 2f08469563550d15cb08a60898d3549720600eee Gitweb: https://git.kernel.org/tip/2f08469563550d15cb08a60898d3549720600eee Author: Paul E. McKenney <paulmck@xxxxxxxxxx> AuthorDate: Mon, 10 Feb 2020 05:29:58 -08:00 Committer: Paul E. McKenney <paulmck@xxxxxxxxxx> CommitterDate: Mon, 27 Apr 2020 11:01:15 -07:00 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: Paul E. McKenney <paulmck@xxxxxxxxxx> --- kernel/rcu/tree.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 156ac8d..c88240a 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -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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