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rcu: Fix synchronize_rcu() for TREE_PREEMPT_RCU

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The redirection of synchronize_sched() to synchronize_rcu() was
appropriate for TREE_RCU, but not for TREE_PREEMPT_RCU.

Fix this by creating an underlying synchronize_sched().  TREE_RCU
then redirects synchronize_rcu() to synchronize_sched(), while
TREE_PREEMPT_RCU has its own version of synchronize_rcu().

Signed-off-by: Paul E. McKenney <[email protected]>
Cc: [email protected]
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LKML-Reference: <12528585111916-git-send-email->
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Paul E. McKenney 2009-09-13 09:15:11 -07:00 • committed by Ingo Molnar
commit 16e3081191
3 changed files with 50 additions and 21 deletions
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44
kernel/rcupdate.c
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@ -74,6 +74,8 @@ void wakeme_after_rcu(struct rcu_head *head)
complete(&rcu->completion);
}
#ifdef CONFIG_TREE_PREEMPT_RCU
/**
* synchronize_rcu - wait until a grace period has elapsed.
*
@ -87,7 +89,7 @@ void synchronize_rcu(void)
{
struct rcu_synchronize rcu;
if (rcu_blocking_is_gp())
if (!rcu_scheduler_active)
return;
init_completion(&rcu.completion);
@ -98,6 +100,46 @@ void synchronize_rcu(void)
}
EXPORT_SYMBOL_GPL(synchronize_rcu);
#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
/**
* synchronize_sched - wait until an rcu-sched grace period has elapsed.
*
* Control will return to the caller some time after a full rcu-sched
* grace period has elapsed, in other words after all currently executing
* rcu-sched read-side critical sections have completed. These read-side
* critical sections are delimited by rcu_read_lock_sched() and
* rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(),
* local_irq_disable(), and so on may be used in place of
* rcu_read_lock_sched().
*
* This means that all preempt_disable code sequences, including NMI and
* hardware-interrupt handlers, in progress on entry will have completed
* before this primitive returns. However, this does not guarantee that
* softirq handlers will have completed, since in some kernels, these
* handlers can run in process context, and can block.
*
* This primitive provides the guarantees made by the (now removed)
* synchronize_kernel() API. In contrast, synchronize_rcu() only
* guarantees that rcu_read_lock() sections will have completed.
* In "classic RCU", these two guarantees happen to be one and
* the same, but can differ in realtime RCU implementations.
*/
void synchronize_sched(void)
{
struct rcu_synchronize rcu;
if (rcu_blocking_is_gp())
return;
init_completion(&rcu.completion);
/* Will wake me after RCU finished. */
call_rcu_sched(&rcu.head, wakeme_after_rcu);
/* Wait for it. */
wait_for_completion(&rcu.completion);
}
EXPORT_SYMBOL_GPL(synchronize_sched);
/**
* synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed.
*