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rcu: Remove never-set needwake assignment from rcu_report_qs_rdp()
The rcu_accelerate_cbs() function is invoked by rcu_report_qs_rdp() only if there is a grace period in progress that is still blocked by at least one CPU on this rcu_node structure. This means that rcu_accelerate_cbs() should never return the value true, and thus that this function should never set the needwake variable and in turn never invoke rcu_gp_kthread_wake(). This commit therefore removes the needwake variable and the invocation of rcu_gp_kthread_wake() in favor of a WARN_ON_ONCE() on the call to rcu_accelerate_cbs(). The purpose of this new WARN_ON_ONCE() is to detect situations where the system's opinion differs from ours. Signed-off-by: Zqiang <qiang1.zhang@intel.com> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
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@ -1955,7 +1955,6 @@ rcu_report_qs_rdp(struct rcu_data *rdp)
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{
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unsigned long flags;
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unsigned long mask;
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bool needwake = false;
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bool needacc = false;
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struct rcu_node *rnp;
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@ -1987,7 +1986,12 @@ rcu_report_qs_rdp(struct rcu_data *rdp)
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* NOCB kthreads have their own way to deal with that...
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*/
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if (!rcu_rdp_is_offloaded(rdp)) {
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needwake = rcu_accelerate_cbs(rnp, rdp);
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/*
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* The current GP has not yet ended, so it
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* should not be possible for rcu_accelerate_cbs()
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* to return true. So complain, but don't awaken.
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*/
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WARN_ON_ONCE(rcu_accelerate_cbs(rnp, rdp));
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} else if (!rcu_segcblist_completely_offloaded(&rdp->cblist)) {
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/*
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* ...but NOCB kthreads may miss or delay callbacks acceleration
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@ -1999,8 +2003,6 @@ rcu_report_qs_rdp(struct rcu_data *rdp)
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rcu_disable_urgency_upon_qs(rdp);
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rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
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/* ^^^ Released rnp->lock */
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if (needwake)
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rcu_gp_kthread_wake();
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if (needacc) {
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rcu_nocb_lock_irqsave(rdp, flags);
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