rcu: prevent call_rcu() from diving into rcu core if irqs disabled
This commit marks a first step towards making call_rcu() have real-time behavior. If irqs are disabled, don't dive into the RCU core. Later on, this new early exit will wake up the per-CPU kthread, which first must be modified to handle the cases involving callback storms. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
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@ -1839,6 +1839,13 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
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/* Add the callback to our list. */
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/* Add the callback to our list. */
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*rdp->nxttail[RCU_NEXT_TAIL] = head;
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*rdp->nxttail[RCU_NEXT_TAIL] = head;
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rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
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rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
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rdp->qlen++;
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/* If interrupts were disabled, don't dive into RCU core. */
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if (irqs_disabled_flags(flags)) {
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local_irq_restore(flags);
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return;
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}
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/*
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/*
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* Force the grace period if too many callbacks or too long waiting.
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* Force the grace period if too many callbacks or too long waiting.
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@ -1847,7 +1854,7 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
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* invoking force_quiescent_state() if the newly enqueued callback
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* invoking force_quiescent_state() if the newly enqueued callback
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* is the only one waiting for a grace period to complete.
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* is the only one waiting for a grace period to complete.
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*/
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*/
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if (unlikely(++rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) {
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if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) {
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/* Are we ignoring a completed grace period? */
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/* Are we ignoring a completed grace period? */
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rcu_process_gp_end(rsp, rdp);
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rcu_process_gp_end(rsp, rdp);
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