rcu: Make __kfree_rcu() less dependent on compiler choices (d8169d4c) · Commits · 戴 / test

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>

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))

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