So I was looking at backporting kfree_rcu(), and came up with this:
#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)
This works, thanks to gcc supporting nested functions, but has one major
issue: any module using call_rcu() must have an rcu_barrier() in its
module_exit() because __kfree_rcu_fn() might be called after the module
is unloaded. For kfree_rcu() this isn't needed since the function called
lives in the base kernel.
I played around with injecting a call to rcu_barrier() into module exit
by modifying module_exit() but I couldn't make the CPP do that. Anyone
else have any ideas?
Another idea I had was to insert the __kfree_rcu_fn() code into the
compat module instead, but I can't see how to do that short of using
some source post-processing scripts.
johannes
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