rcu: Make cond_resched_rcu_qs() supply RCU-sched expedited QS

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Although cond_resched_rcu_qs() supplies quiescent states to all flavors
of normal RCU grace periods, it does nothing for expedited RCU-sched
grace periods.  This commit therefore adds a check for a need for a
quiescent state from the current CPU by an expedited RCU-sched grace
period, and invokes rcu_sched_qs() to supply that quiescent state if so.

Note that the check is racy in that we might be migrated to some other
CPU just after checking the per-CPU variable.  This is OK because the
act of migration will do a context switch, which will supply the needed
quiescent state.  The only downside is that we might do an unnecessary
call to rcu_sched_qs(), but the probability is low and the overhead
is small.

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

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This commit is contained in:

Paul E. McKenney 2016-01-13 13:57:54 -08:00

parent 251c617c75

commit a1e1224849

1 changed files with 15 additions and 0 deletions

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kernel/rcu/tree.c

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