Merge branch 'rcu/next' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu into core/urgent
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15
init/Kconfig
15
init/Kconfig
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@ -497,21 +497,6 @@ config RCU_BOOST_DELAY
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Accept the default if unsure.
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config SRCU_SYNCHRONIZE_DELAY
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int "Microseconds to delay before waiting for readers"
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range 0 20
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default 10
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help
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This option controls how long SRCU delays before entering its
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loop waiting on SRCU readers. The purpose of this loop is
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to avoid the unconditional context-switch penalty that would
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otherwise be incurred if there was an active SRCU reader,
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in a manner similar to adaptive locking schemes. This should
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be set to be a bit longer than the common-case SRCU read-side
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critical-section overhead.
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Accept the default if unsure.
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endmenu # "RCU Subsystem"
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config IKCONFIG
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@ -189,7 +189,8 @@ static int rcu_kthread(void *arg)
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unsigned long flags;
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for (;;) {
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wait_event(rcu_kthread_wq, have_rcu_kthread_work != 0);
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wait_event_interruptible(rcu_kthread_wq,
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have_rcu_kthread_work != 0);
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morework = rcu_boost();
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local_irq_save(flags);
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work = have_rcu_kthread_work;
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@ -155,6 +155,16 @@ void __srcu_read_unlock(struct srcu_struct *sp, int idx)
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}
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EXPORT_SYMBOL_GPL(__srcu_read_unlock);
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/*
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* We use an adaptive strategy for synchronize_srcu() and especially for
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* synchronize_srcu_expedited(). We spin for a fixed time period
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* (defined below) to allow SRCU readers to exit their read-side critical
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* sections. If there are still some readers after 10 microseconds,
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* we repeatedly block for 1-millisecond time periods. This approach
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* has done well in testing, so there is no need for a config parameter.
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*/
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#define SYNCHRONIZE_SRCU_READER_DELAY 10
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/*
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* Helper function for synchronize_srcu() and synchronize_srcu_expedited().
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*/
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@ -207,11 +217,12 @@ static void __synchronize_srcu(struct srcu_struct *sp, void (*sync_func)(void))
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* will have finished executing. We initially give readers
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* an arbitrarily chosen 10 microseconds to get out of their
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* SRCU read-side critical sections, then loop waiting 1/HZ
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* seconds per iteration.
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* seconds per iteration. The 10-microsecond value has done
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* very well in testing.
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*/
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if (srcu_readers_active_idx(sp, idx))
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udelay(CONFIG_SRCU_SYNCHRONIZE_DELAY);
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udelay(SYNCHRONIZE_SRCU_READER_DELAY);
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while (srcu_readers_active_idx(sp, idx))
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schedule_timeout_interruptible(1);
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