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Commit 0d39482c authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Provide rcu_expedite_gp() and rcu_unexpedite_gp() 



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: default avatarArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent c517d838

include/linux/rcupdate.h

+20 −0
Original line number Diff line number Diff line
@@ -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,

kernel/rcu/update.c

+48 −0
Original line number Diff line number Diff line
@@ -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



/*