Commit-ID: 2655d57ef35aa327a2e58a1c5dc7b65c65003f4e
Gitweb: http://git.kernel.org/tip/2655d57ef35aa327a2e58a1c5dc7b65c65003f4e
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Thu, 7 Apr 2011 22:47:23 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Thu, 5 May 2011 23:16:59 -0700
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@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
---
kernel/rcutree.c | 9 ++++++++-
1 files changed, 8 insertions(+), 1 deletions(-)
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 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
/* 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 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
* 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);
--
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