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>
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index fe85600..78923a5 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1839,6 +1839,13 @@
/* Add the callback to our list. */
*rdp->nxttail[RCU_NEXT_TAIL] = head;
rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
+ rdp->qlen++;
+
+ /* If interrupts were disabled, don't dive into RCU core. */
+ if (irqs_disabled_flags(flags)) {
+ local_irq_restore(flags);
+ return;
+ }
/*
* Force the grace period if too many callbacks or too long waiting.
@@ -1847,7 +1854,7 @@
* invoking force_quiescent_state() if the newly enqueued callback
* is the only one waiting for a grace period to complete.
*/
- if (unlikely(++rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) {
+ if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) {
/* Are we ignoring a completed grace period? */
rcu_process_gp_end(rsp, rdp);
