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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2009-01-04 14:41:11 -0500
committerIngo Molnar <mingo@elte.hu>2009-01-05 04:12:33 -0500
commit90a4d2c0106bb690f0b6af3d506febc35c658aa7 (patch)
treef62ee471a6d94fd94bfe97be339ab30ce7814e6f
parentc12172c0251761c54260376eb29a5f6547495580 (diff)
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>
-rw-r--r--kernel/rcutree.c12
1 files changed, 4 insertions, 8 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 88d921c5c449..f2d8638e6c60 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);
79DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); 79DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
80 80
81#ifdef CONFIG_NO_HZ 81#ifdef CONFIG_NO_HZ
82DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks); 82DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
83 .dynticks_nesting = 1,
84 .dynticks = 1,
85};
83#endif /* #ifdef CONFIG_NO_HZ */ 86#endif /* #ifdef CONFIG_NO_HZ */
84 87
85static int blimit = 10; /* Maximum callbacks per softirq. */ 88static int blimit = 10; /* Maximum callbacks per softirq. */
@@ -1380,13 +1383,6 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
1380 1383
1381static void __cpuinit rcu_online_cpu(int cpu) 1384static void __cpuinit rcu_online_cpu(int cpu)
1382{ 1385{
1383#ifdef CONFIG_NO_HZ
1384 struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
1385
1386 rdtp->dynticks_nesting = 1;
1387 rdtp->dynticks |= 1; /* need consecutive #s even for hotplug. */
1388 rdtp->dynticks_nmi = (rdtp->dynticks_nmi + 1) & ~0x1;
1389#endif /* #ifdef CONFIG_NO_HZ */
1390 rcu_init_percpu_data(cpu, &rcu_state); 1386 rcu_init_percpu_data(cpu, &rcu_state);
1391 rcu_init_percpu_data(cpu, &rcu_bh_state); 1387 rcu_init_percpu_data(cpu, &rcu_bh_state);
1392 open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); 1388 open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);