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authorJan Engelhardt <jengelh@medozas.de>2012-04-19 11:44:39 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2012-04-24 20:54:51 -0700
commitd8169d4c369e8aa2fda10df705a4957331b5a4db (patch)
treece8a08d5bd1a58f5e4703f39b2cc2033a8b03994 /include/linux/rcupdate.h
parentc9336643e1440f4dfc89ad4ac6185813619abb8c (diff)
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 <jengelh@medozas.de> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'include/linux/rcupdate.h')
-rw-r--r--include/linux/rcupdate.h18
1 files changed, 18 insertions, 0 deletions
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))