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rcu: Make __kfree_rcu() less dependent on compiler choices

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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: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit is contained in:
Jan Engelhardt 2012-04-19 11:44:39 -07:00 committed by Paul E. McKenney
parent c9336643e1
commit d8169d4c36
1 changed files with 18 additions and 0 deletions
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18
include/linux/rcupdate.h
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@ -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))