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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2016-12-16 02:37:47 +0300 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-01-23 22:37:13 +0300 |
| commit | 630c7ed9ca0608912fa7c8591d05dfc8742dc9e6 (patch) | |
| tree | 84bfe23f7d6f71cb5843c4218e543176e8cb6079 | |
| parent | 1626c365f8e60bbe790605dc475847f070927dd7 (diff) | |
| download | linux-630c7ed9ca0608912fa7c8591d05dfc8742dc9e6.tar.xz | |
rcu: Don't wake rcuc/X kthreads on NOCB CPUs
Chris Friesen notice that rcuc/X kthreads were consuming CPU even on
NOCB CPUs. This makes no sense because the only purpose or these
kthreads is to invoke normal (non-offloaded) callbacks, of which there
will never be any on NOCB CPUs. This problem was due to a bug in
cpu_has_callbacks_ready_to_invoke(), which should have been checking
->nxttail[RCU_NEXT_TAIL] for NULL, but which was instead (incorrectly)
checking ->nxttail[RCU_DONE_TAIL]. Because ->nxttail[RCU_DONE_TAIL] is
never NULL, the only effect is to cause the rcuc/X kthread to execute
when it should not do so.
This commit therefore checks ->nxttail[RCU_NEXT_TAIL], which is NULL
for NOCB CPUs.
Reported-by: Chris Friesen <chris.friesen@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
| -rw-r--r-- | kernel/rcu/tree.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index d7b63b88434b..be2301238a23 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -611,7 +611,7 @@ static int cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) { return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL] && - rdp->nxttail[RCU_DONE_TAIL] != NULL; + rdp->nxttail[RCU_NEXT_TAIL] != NULL; } /* |