rcu: Avoid tick_dep_set_cpu() misordering

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In the current code, rcu_nmi_enter_common() might decide to turn on
the tick using tick_dep_set_cpu(), but be delayed just before doing so.
Then the grace-period kthread might notice that the CPU in question had
in fact gone through a quiescent state, thus turning off the tick using
tick_dep_clear_cpu().  The later invocation of tick_dep_set_cpu() would
then incorrectly leave the tick on.

This commit therefore enlists the aid of the leaf rcu_node structure's
->lock to ensure that decisions to enable or disable the tick are
carried out before they can be reversed.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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This commit is contained in:

Paul E. McKenney 2019-11-26 18:05:45 -08:00

parent 77339e61aa

commit 5b14557b07

1 changed files with 9 additions and 3 deletions

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kernel/rcu/tree.c

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