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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-01-22 18:24:08 -0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-03-11 13:22:38 -0700
commit37745d281069682d901f00c0121949a7d224195f (patch)
tree0c15fd487faa046a257336b4205572b066873ca7 /kernel/rcu
parent237a0f2193c6daf9b1edd7fd15d55e680f268952 (diff)
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rcu: Provide diagnostic option to slow down grace-period initialization
Grace-period initialization normally proceeds quite quickly, so that it is very difficult to reproduce races against grace-period initialization. This commit therefore allows grace-period initialization to be artificially slowed down, increasing race-reproduction probability. A pair of new Kconfig parameters are provided, CONFIG_RCU_TORTURE_TEST_SLOW_INIT to enable the slowdowns, and CONFIG_RCU_TORTURE_TEST_SLOW_INIT_DELAY to specify the number of jiffies of slowdown to apply. A boot-time parameter named rcutree.gp_init_delay allows boot-time delay to be specified. By default, no delay will be applied even if CONFIG_RCU_TORTURE_TEST_SLOW_INIT is set. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu')
-rw-r--r--kernel/rcu/tree.c10
1 files changed, 10 insertions, 0 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 3b7e4133ca99..b42001fd55fb 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -160,6 +160,12 @@ static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
static int kthread_prio = CONFIG_RCU_KTHREAD_PRIO;
module_param(kthread_prio, int, 0644);
+/* Delay in jiffies for grace-period initialization delays. */
+static int gp_init_delay = IS_ENABLED(CONFIG_RCU_TORTURE_TEST_SLOW_INIT)
+ ? CONFIG_RCU_TORTURE_TEST_SLOW_INIT_DELAY
+ : 0;
+module_param(gp_init_delay, int, 0644);
+
/*
* Track the rcutorture test sequence number and the update version
* number within a given test. The rcutorture_testseq is incremented
@@ -1769,6 +1775,10 @@ static int rcu_gp_init(struct rcu_state *rsp)
raw_spin_unlock_irq(&rnp->lock);
cond_resched_rcu_qs();
ACCESS_ONCE(rsp->gp_activity) = jiffies;
+ if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_SLOW_INIT) &&
+ gp_init_delay > 0 &&
+ !(rsp->gpnum % (rcu_num_nodes * 10)))
+ schedule_timeout_uninterruptible(gp_init_delay);
}
mutex_unlock(&rsp->onoff_mutex);