From: Jan Engelhardt Date: Thu, 19 Apr 2012 18:44:39 +0000 (-0700) Subject: rcu: Make __kfree_rcu() less dependent on compiler choices X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=d8169d4c;p=linux-beck.git 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: Jan Engelhardt Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 20fb776a1d4a..d5dfb109dfe1 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -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))