rcu: Suppress false-positive offline-CPU lockdep-RCU splat

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The rcu_lockdep_current_cpu_online() function currently checks only the
RCU-sched data structures to determine whether or not RCU believes that a
given CPU is offline.  Unfortunately, there are multiple flavors of RCU,
which means that there is a short window of time during which the various
flavors disagree as to whether or not a given CPU is offline.  This can
result in false-positive lockdep-RCU splats in which some other flavor
of RCU tries to do something based on its view that the CPU is online,
only to get hit with a lockdep-RCU splat because RCU-sched instead
believes that the CPU is offline.

This commit therefore changes rcu_lockdep_current_cpu_online() to scan
all RCU flavors and to consider a given CPU to be online if any of the
RCU flavors believe it to be online, thus preventing these false-positive
splats.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

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This commit is contained in:

Paul E. McKenney 2018-05-15 10:14:34 -07:00

parent 928164351e

commit 5554788e1d

1 changed files with 24 additions and 24 deletions

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kernel/rcu/tree.c

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