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Commit d8169d4c authored by Jan Engelhardt's avatar Jan Engelhardt Committed by Paul E. McKenney
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rcu: Make __kfree_rcu() less dependent on compiler choices 



Currently, __kfree_rcu() is implemented as an inline function, and
contains a BUILD_BUG_ON() that malfunctions if __kfree_rcu() is compiled
as an out-of-line function.  Unfortunately, there are compiler settings
(e.g., -O0) that can result in __kfree_rcu() being compiled out of line,
resulting in annoying build breakage.  This commit therefore converts
both __kfree_rcu() and __is_kfree_rcu_offset() from inline functions to
macros to prevent such misbehavior on the part of the compiler.

Signed-off-by: default avatarJan Engelhardt <jengelh@medozas.de>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
parent c9336643

include/linux/rcupdate.h

+18 −0
Original line number Diff line number Diff line
@@ -922,6 +922,21 @@ void __kfree_rcu(struct rcu_head *head, unsigned long offset) 
	kfree_call_rcu(head, (rcu_callback)offset);

}



/*

 * Does the specified offset indicate that the corresponding rcu_head

 * structure can be handled by kfree_rcu()?

 */

#define __is_kfree_rcu_offset(offset) ((offset) < 4096)



/*

 * Helper macro for kfree_rcu() to prevent argument-expansion eyestrain.

 */

#define __kfree_rcu(head, offset) \

	do { \

		BUILD_BUG_ON(!__is_kfree_rcu_offset(offset)); \

		call_rcu(head, (void (*)(struct rcu_head *))(unsigned long)(offset)); \

	} while (0)



/**

 * kfree_rcu() - kfree an object after a grace period.

 * @ptr:	pointer to kfree
@@ -944,6 +959,9 @@ void __kfree_rcu(struct rcu_head *head, unsigned long offset) 
 *

 * Note that the allowable offset might decrease in the future, for example,

 * to allow something like kmem_cache_free_rcu().

 *

 * The BUILD_BUG_ON check must not involve any function calls, hence the

 * checks are done in macros here.

 */

#define kfree_rcu(ptr, rcu_head)					\

	__kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))