From 2655d57ef35aa327a2e58a1c5dc7b65c65003f4e Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 7 Apr 2011 22:47:23 -0700 Subject: [PATCH] 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 Reviewed-by: Josh Triplett --- kernel/rcutree.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/kernel/rcutree.c b/kernel/rcutree.c index fe85600ba8c2..78923a50cdb2 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); -- 2.39.5