diff options
| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2010-03-18 21:36:51 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2010-05-10 11:08:31 -0700 |
| commit | d25eb9442bb2c38c1e742f0fa764d7132d72593f (patch) | |
| tree | 0a2604a3b61ce7a0868c021ac945d9826e0d88f1 /kernel/rcutree.c | |
| parent | 2b3fc35f6919344e3cf722dde8308f47235c0b70 (diff) | |
rcu: substitute set_need_resched for sending resched IPIs
This patch adds a check to __rcu_pending() that does a local
set_need_resched() if the current CPU is holding up the current grace
period and if force_quiescent_state() will be called soon. The goal is
to reduce the probability that force_quiescent_state() will need to do
smp_send_reschedule(), which sends an IPI and is therefore more expensive
on most architectures.
Signed-off-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcutree.c')
| -rw-r--r-- | kernel/rcutree.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 3ec8160fc75..e54c1235122 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1499,6 +1499,16 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) /* Is the RCU core waiting for a quiescent state from this CPU? */ if (rdp->qs_pending) { + + /* + * If force_quiescent_state() coming soon and this CPU + * needs a quiescent state, and this is either RCU-sched + * or RCU-bh, force a local reschedule. + */ + if (!rdp->preemptable && + ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs) - 1, + jiffies)) + set_need_resched(); rdp->n_rp_qs_pending++; return 1; } |