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Merge branch 'rcu/next' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu into core/urgent

This commit is contained in:
Ingo Molnar 2011-01-14 15:30:16 +01:00
parent f123c98e7f b24efdfdf6
commit 1161ec9449
3 changed files with 15 additions and 18 deletions
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15
init/Kconfig
View File

@ -497,21 +497,6 @@ config RCU_BOOST_DELAY
Accept the default if unsure.
config SRCU_SYNCHRONIZE_DELAY
int "Microseconds to delay before waiting for readers"
range 0 20
default 10
help
This option controls how long SRCU delays before entering its
loop waiting on SRCU readers. The purpose of this loop is
to avoid the unconditional context-switch penalty that would
otherwise be incurred if there was an active SRCU reader,
in a manner similar to adaptive locking schemes. This should
be set to be a bit longer than the common-case SRCU read-side
critical-section overhead.
Accept the default if unsure.
endmenu # "RCU Subsystem"
config IKCONFIG

3
kernel/rcutiny.c
View File

@ -189,7 +189,8 @@ static int rcu_kthread(void *arg)
unsigned long flags;
for (;;) {
wait_event(rcu_kthread_wq, have_rcu_kthread_work != 0);
wait_event_interruptible(rcu_kthread_wq,
have_rcu_kthread_work != 0);
morework = rcu_boost();
local_irq_save(flags);
work = have_rcu_kthread_work;

15
kernel/srcu.c
View File

@ -155,6 +155,16 @@ void __srcu_read_unlock(struct srcu_struct *sp, int idx)
}
EXPORT_SYMBOL_GPL(__srcu_read_unlock);
/*
* We use an adaptive strategy for synchronize_srcu() and especially for
* synchronize_srcu_expedited(). We spin for a fixed time period
* (defined below) to allow SRCU readers to exit their read-side critical
* sections. If there are still some readers after 10 microseconds,
* we repeatedly block for 1-millisecond time periods. This approach
* has done well in testing, so there is no need for a config parameter.
*/
#define SYNCHRONIZE_SRCU_READER_DELAY 10
/*
* Helper function for synchronize_srcu() and synchronize_srcu_expedited().
*/
@ -207,11 +217,12 @@ static void __synchronize_srcu(struct srcu_struct *sp, void (*sync_func)(void))
* will have finished executing. We initially give readers
* an arbitrarily chosen 10 microseconds to get out of their
* SRCU read-side critical sections, then loop waiting 1/HZ
* seconds per iteration.
* seconds per iteration. The 10-microsecond value has done
* very well in testing.
*/
if (srcu_readers_active_idx(sp, idx))
udelay(CONFIG_SRCU_SYNCHRONIZE_DELAY);
udelay(SYNCHRONIZE_SRCU_READER_DELAY);
while (srcu_readers_active_idx(sp, idx))
schedule_timeout_interruptible(1);