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Subject[PATCH 2/3] srcu: queue work without holding the lock
Date
On RT we can't invoke queue_delayed_work() within an atomic section
(which is provided by raw_spin_lock_irqsave()).
srcu_reschedule() invokes queue_delayed_work() outside of the
raw_spin_lock_irq_rcu_node() section so this should be fine here, too.
If the remaining callers of call_srcu() aren't atomic
(spin_lock_irqsave() is fine) then this should work on RT, too.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
kernel/rcu/srcutree.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index d190af0e56f8..3ee4ef40f23e 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -648,12 +648,17 @@ static void srcu_funnel_gp_start(struct srcu_struct *sp, struct srcu_data *sdp,
/* If grace period not already done and none in progress, start it. */
if (!rcu_seq_done(&sp->srcu_gp_seq, s) &&
rcu_seq_state(sp->srcu_gp_seq) == SRCU_STATE_IDLE) {
+ unsigned long delay;
+
WARN_ON_ONCE(ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed));
srcu_gp_start(sp);
+ delay = srcu_get_delay(sp);
+ raw_spin_unlock_irqrestore_rcu_node(sp, flags);
+
queue_delayed_work(system_power_efficient_wq, &sp->work,
- srcu_get_delay(sp));
- }
- raw_spin_unlock_irqrestore_rcu_node(sp, flags);
+ delay);
+ } else
+ raw_spin_unlock_irqrestore_rcu_node(sp, flags);
}

/*
--
2.14.1
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