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Commit 15c7c972 authored by Paul E. McKenney's avatar Paul E. McKenney
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rcu: Use *_ONCE() to protect lockless ->expmask accesses

The rcu_node structure's ->expmask field is accessed locklessly when
starting a new expedited grace period and when reporting an expedited
RCU CPU stall warning.  This commit therefore handles the former by
taking a snapshot of ->expmask while the lock is held and the latter
by applying READ_ONCE() to lockless reads and WRITE_ONCE() to the
corresponding updates.

Link: https://lore.kernel.org/lkml/CANpmjNNmSOagbTpffHr4=Yedckx9Rm2NuGqC9UqE+AOz5f1-ZQ@mail.gmail.com


Reported-by: default avatar <syzbot+134336b86f728d6e55a0@syzkaller.appspotmail.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Acked-by: default avatarMarco Elver <elver@google.com>
parent e42617b8
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