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rcu: Fix exp_funnel_lock()/rcu_exp_wait_wake() datarace
authorPaul E. McKenney <paulmck@kernel.org>
Mon, 23 Dec 2019 03:55:50 +0000 (19:55 -0800)
committerPaul E. McKenney <paulmck@kernel.org>
Thu, 20 Feb 2020 23:58:21 +0000 (15:58 -0800)
commit24bb9eccf7ff335c16c2970ac7cd5c32a92821a6
tree149776c467fb08dc619d26f77565ac3b90b31a8d
parent82dd8419e225958f01708cda8a3fc6c3c5356228
rcu: Fix exp_funnel_lock()/rcu_exp_wait_wake() datarace

The rcu_node structure's ->exp_seq_rq field is accessed locklessly, so
updates must use WRITE_ONCE().  This commit therefore adds the needed
WRITE_ONCE() invocation where it was missed.

This data race was reported by KCSAN.  Not appropriate for backporting
due to failure being unlikely.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
kernel/rcu/tree_exp.h