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rcu: Provide rcu_expedite_gp() and rcu_unexpedite_gp()

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Currently, expediting of normal synchronous grace-period primitives
(synchronize_rcu() and friends) is controlled by the rcu_expedited()
boot/sysfs parameter.  This works well, but does not handle nesting.
This commit therefore provides rcu_expedite_gp() to enable expediting
and rcu_unexpedite_gp() to cancel a prior rcu_expedite_gp(), both of
which support nesting.

Reported-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2015-02-18 12:24:30 -08:00
parent c517d838eb
commit 0d39482c3d
2 changed files with 68 additions and 0 deletions
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20
include/linux/rcupdate.h
View File

@ -48,6 +48,26 @@
extern int rcu_expedited; /* for sysctl */
#ifdef CONFIG_TINY_RCU
/* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */
static inline bool rcu_gp_is_expedited(void) /* Internal RCU use. */
{
return false;
}
static inline void rcu_expedite_gp(void)
{
}
static inline void rcu_unexpedite_gp(void)
{
}
#else /* #ifdef CONFIG_TINY_RCU */
bool rcu_gp_is_expedited(void); /* Internal RCU use. */
void rcu_expedite_gp(void);
void rcu_unexpedite_gp(void);
#endif /* #else #ifdef CONFIG_TINY_RCU */
enum rcutorture_type {
RCU_FLAVOR,
RCU_BH_FLAVOR,

48
kernel/rcu/update.c
View File

@ -62,6 +62,54 @@ MODULE_ALIAS("rcupdate");
module_param(rcu_expedited, int, 0);
#ifndef CONFIG_TINY_RCU
static atomic_t rcu_expedited_nesting;
/*
* Should normal grace-period primitives be expedited? Intended for
* use within RCU. Note that this function takes the rcu_expedited
* sysfs/boot variable into account as well as the rcu_expedite_gp()
* nesting. So looping on rcu_unexpedite_gp() until rcu_gp_is_expedited()
* returns false is a -really- bad idea.
*/
bool rcu_gp_is_expedited(void)
{
return rcu_expedited || atomic_read(&rcu_expedited_nesting);
}
EXPORT_SYMBOL_GPL(rcu_gp_is_expedited);
/**
* rcu_expedite_gp - Expedite future RCU grace periods
*
* After a call to this function, future calls to synchronize_rcu() and
* friends act as the corresponding synchronize_rcu_expedited() function
* had instead been called.
*/
void rcu_expedite_gp(void)
{
atomic_inc(&rcu_expedited_nesting);
}
EXPORT_SYMBOL_GPL(rcu_expedite_gp);
/**
* rcu_unexpedite_gp - Cancel prior rcu_expedite_gp() invocation
*
* Undo a prior call to rcu_expedite_gp(). If all prior calls to
* rcu_expedite_gp() are undone by a subsequent call to rcu_unexpedite_gp(),
* and if the rcu_expedited sysfs/boot parameter is not set, then all
* subsequent calls to synchronize_rcu() and friends will return to
* their normal non-expedited behavior.
*/
void rcu_unexpedite_gp(void)
{
atomic_dec(&rcu_expedited_nesting);
}
EXPORT_SYMBOL_GPL(rcu_unexpedite_gp);
#endif /* #ifndef CONFIG_TINY_RCU */
#ifdef CONFIG_PREEMPT_RCU
/*