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authorPaul E. McKenney <paul.mckenney@linaro.org>2011-11-22 20:43:02 -0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2011-12-11 10:32:02 -0800
commitf535a607c13c7b674e0788ca5765779aa74a01c3 (patch)
tree433a07d16ff11d9f67e7991831cebf3cadfd9939 /kernel/rcutree.c
parent84ad00cb61f1cb21f0b63bc6f7dc254399eb3830 (diff)
downloadop-kernel-dev-f535a607c13c7b674e0788ca5765779aa74a01c3.zip
op-kernel-dev-f535a607c13c7b674e0788ca5765779aa74a01c3.tar.gz
rcu: Eliminate RCU_FAST_NO_HZ grace-period hang
With the new implementation of RCU_FAST_NO_HZ, it was possible to hang RCU grace periods as follows: o CPU 0 attempts to go idle, cycles several times through the rcu_prepare_for_idle() loop, then goes dyntick-idle when RCU needs nothing more from it, while still having at least on RCU callback pending. o CPU 1 goes idle with no callbacks. Both CPUs can then stay in dyntick-idle mode indefinitely, preventing the RCU grace period from ever completing, possibly hanging the system. This commit therefore prevents CPUs that have RCU callbacks from entering dyntick-idle mode. This approach also eliminates the need for the end-of-grace-period IPIs used previously. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcutree.c')
-rw-r--r--kernel/rcutree.c2
1 files changed, 0 insertions, 2 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 7fb8b0e..13fab4a 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1086,7 +1086,6 @@ static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
* callbacks are waiting on the grace period that just now
* completed.
*/
- rcu_schedule_wake_gp_end();
if (*rdp->nxttail[RCU_WAIT_TAIL] == NULL) {
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
@@ -1672,7 +1671,6 @@ static void rcu_process_callbacks(struct softirq_action *unused)
&__get_cpu_var(rcu_sched_data));
__rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data));
rcu_preempt_process_callbacks();
- rcu_wake_cpus_for_gp_end();
trace_rcu_utilization("End RCU core");
}
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