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rcu: Modulate grace-period slow init to normalize delay
Currently, the larger the gp_init_delay boot parameter, the slower rcutorture will sequence through grace periods. This commit avoids this issue by decreasing the probability of slowing initialization of a given grace period as the degree of slowness increases. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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1 changed files with 13 additions and 2 deletions
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@ -169,7 +169,17 @@ module_param(gp_init_delay, int, 0644);
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#else /* #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_INIT */
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static const int gp_init_delay;
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#endif /* #else #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_INIT */
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#define PER_RCU_NODE_PERIOD 10 /* Number of grace periods between delays. */
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/*
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* Number of grace periods between delays, normalized by the duration of
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* the delay. The longer the the delay, the more the grace periods between
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* each delay. The reason for this normalization is that it means that,
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* for non-zero delays, the overall slowdown of grace periods is constant
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* regardless of the duration of the delay. This arrangement balances
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* the need for long delays to increase some race probabilities with the
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* need for fast grace periods to increase other race probabilities.
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*/
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#define PER_RCU_NODE_PERIOD 3 /* Number of grace periods between delays. */
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/*
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* Track the rcutorture test sequence number and the update version
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@ -1848,7 +1858,8 @@ static int rcu_gp_init(struct rcu_state *rsp)
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cond_resched_rcu_qs();
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WRITE_ONCE(rsp->gp_activity, jiffies);
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if (gp_init_delay > 0 &&
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!(rsp->gpnum % (rcu_num_nodes * PER_RCU_NODE_PERIOD)))
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!(rsp->gpnum %
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(rcu_num_nodes * PER_RCU_NODE_PERIOD * gp_init_delay)))
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schedule_timeout_uninterruptible(gp_init_delay);
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}
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