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rcu: Make rcu_future_needs_gp() check all ->need_future_gps[] elements 

Currently, the rcu_future_needs_gp() function checks only the current
element of the ->need_future_gps[] array, which might miss elements that
were offset from the expected element, for example, due to races with
the start or the end of a grace period.  This commit therefore makes
rcu_future_needs_gp() use the need_any_future_gp() macro to check all
of the elements of this array.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>
This commit is contained in:
Paul E. McKenney 2018-04-18 14:14:42 -07:00
parent 51af970d19
commit 0ae94e00ce
2 changed files with 3 additions and 2 deletions
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2
kernel/rcu/tree.c
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@ -720,7 +720,7 @@ static int rcu_future_needs_gp(struct rcu_state *rsp)
struct rcu_node *rnp = rcu_get_root(rsp);
lockdep_assert_irqs_disabled();
return READ_ONCE(need_future_gp_element(rnp, rnp->completed));
return need_any_future_gp(rnp);
}
/*

3
kernel/rcu/tree.h
View File

@ -169,7 +169,8 @@ struct rcu_node {
bool __nonzero = false; \
\
for (__i = 0; __i < ARRAY_SIZE((rnp)->need_future_gp); __i++) \
__nonzero = __nonzero || (rnp)->need_future_gp[__i]; \
__nonzero = __nonzero || \
READ_ONCE((rnp)->need_future_gp[__i]); \
__nonzero; \
})