This adds a nested function everywhere kfree_rcu() was called. This
function frees the memory and is given as a function to call_rcu().
The kfree_rcu define was mad by Johannes Berg.
The rcu callback could happen every time also after the module was
unloaded and this will cause problems.
A rcu_barrier() was added into every module_exit so that this will not
be called after the module was unloaded.
The define overwriting module_exit is based on the original module_exit
which looks like this:
/* This is only required if you want to be unloadable. */
/#define module_exit(exitfn) \
static inline exitcall_t __exittest(void) \
{ return exitfn; } \
void cleanup_module(void) __attribute__((alias(#exitfn)));
We replaced the call to the actual function exitfn() with a call to our
function which calls the original exitfn() and then rcu_barrier()
As a module will not be unloaded that ofter it should not have a big
performance impact when rcu_barrier() is called on every module exit,
also when no kfree_rcu() backport is used in that module.
Signed-off-by: Hauke Mehrtens <hauke@xxxxxxxxxx>
CC: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
---
include/linux/compat-3.0.h | 48 ++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 48 insertions(+), 0 deletions(-)
diff --git a/include/linux/compat-3.0.h b/include/linux/compat-3.0.h
index 8c8720e..56639fd 100644
--- a/include/linux/compat-3.0.h
+++ b/include/linux/compat-3.0.h
@@ -5,6 +5,8 @@
#if (LINUX_VERSION_CODE < KERNEL_VERSION(3,0,0))
+#include <linux/rcupdate.h>
+
/*
* since commit 1c5cae815d19ffe02bdfda1260949ef2b1806171
* "net: call dev_alloc_name from register_netdevice" dev_alloc_name is
@@ -79,6 +81,52 @@ static inline int __must_check kstrtos32_from_user(const char __user *s, size_t
return kstrtoint_from_user(s, count, base, res);
}
+/*
+ * This adds a nested function everywhere kfree_rcu() was called. This
+ * function frees the memory and is given as a function to call_rcu().
+ * The rcu callback could happen every time also after the module was
+ * unloaded and this will cause problems.
+ */
+#define kfree_rcu(data, rcuhead) do { \
+ void __kfree_rcu_fn(struct rcu_head *rcu_head) \
+ { \
+ void *___ptr; \
+ ___ptr = container_of(rcu_head, typeof(*(data)), rcuhead);\
+ kfree(___ptr); \
+ } \
+ call_rcu(&(data)->rcuhead, __kfree_rcu_fn); \
+ } while (0)
+
+#ifdef MODULE
+
+/*
+ * The define overwriting module_exit is based on the original module_exit
+ * which looks like this:
+ * #define module_exit(exitfn) \
+ * static inline exitcall_t __exittest(void) \
+ * { return exitfn; } \
+ * void cleanup_module(void) __attribute__((alias(#exitfn)));
+ *
+ * We replaced the call to the actual function exitfn() with a call to our
+ * function which calls the original exitfn() and then rcu_barrier()
+ *
+ * As a module will not be unloaded that ofter it should not have a big
+ * performance impact when rcu_barrier() is called on every module exit,
+ * also when no kfree_rcu() backport is used in that module.
+ */
+#undef module_exit
+#define module_exit(exitfn) \
+ static inline exitcall_t __exittest(void) \
+ { return exitfn; } \
+ void __exit __exit_compat(void) \
+ { \
+ exitfn(); \
+ rcu_barrier(); \
+ } \
+ void cleanup_module(void) __attribute__((alias("__exit_compat")));
+
+#endif
+
#endif /* (LINUX_VERSION_CODE < KERNEL_VERSION(3,0,0)) */
#endif /* LINUX_3_0_COMPAT_H */
--
1.7.4.1
--
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