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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2009-01-04 11:41:11 -0800
committerIngo Molnar <mingo@elte.hu>2009-01-05 10:12:33 +0100
commit90a4d2c0106bb690f0b6af3d506febc35c658aa7 (patch)
treef62ee471a6d94fd94bfe97be339ab30ce7814e6f /kernel
parentc12172c0251761c54260376eb29a5f6547495580 (diff)
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rcu: make treercu safe for suspend and resume
Impact: fix kernel warnings [and potential crash] during suspend+resume Kudos to both Dhaval Giani and Jens Axboe for finding a bug in treercu that causes warnings after suspend-resume cycles in Dhaval's case and during stress tests in Jens's case. It would also probably cause failures if heavily stressed. The solution, ironically enough, is to revert to rcupreempt's code for initializing the dynticks state. And the patch even results in smaller code -- so what was I thinking??? This is 2.6.29 material, given that people really do suspend and resume Linux these days. ;-) Reported-by: Dhaval Giani <dhaval@linux.vnet.ibm.com> Reported-by: Jens Axboe <jens.axboe@oracle.com> Tested-by: Dhaval Giani <dhaval@linux.vnet.ibm.com> Tested-by: Jens Axboe <jens.axboe@oracle.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/rcutree.c12
1 files changed, 4 insertions, 8 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 88d921c5c44..f2d8638e6c6 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -79,7 +79,10 @@ struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state);
DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
#ifdef CONFIG_NO_HZ
-DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks);
+DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
+ .dynticks_nesting = 1,
+ .dynticks = 1,
+};
#endif /* #ifdef CONFIG_NO_HZ */
static int blimit = 10; /* Maximum callbacks per softirq. */
@@ -1380,13 +1383,6 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
static void __cpuinit rcu_online_cpu(int cpu)
{
-#ifdef CONFIG_NO_HZ
- struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
-
- rdtp->dynticks_nesting = 1;
- rdtp->dynticks |= 1; /* need consecutive #s even for hotplug. */
- rdtp->dynticks_nmi = (rdtp->dynticks_nmi + 1) & ~0x1;
-#endif /* #ifdef CONFIG_NO_HZ */
rcu_init_percpu_data(cpu, &rcu_state);
rcu_init_percpu_data(cpu, &rcu_bh_state);
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);