Hi Johannes,
now your patch using kfree_rcu went into linux-next. ;-)
On 10/18/2011 10:18 AM, Johannes Berg wrote:
> 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.
This looks nice to me.
> 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?
I played around with module_exit and modified the define into the
following. Now rcu_barrier() gets called on every module_exit. As
modules are not unloaded so often it should not hurd that this is also
done when unloading a module not using kfree_rcu().
#undef module_exit
#define module_exit(exitfn) \
void __exit __exit_rcu_barrier(void) \
{ \
exitfn(); \
rcu_barrier(); \
} \
static inline exitcall_t __exittest(void) \
{ return exitfn; } \
void cleanup_module(void) __attribute__((alias("__exit_rcu_barrier")));
>
> 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 are you fine with this?
Hauke
--
To unsubscribe from this list: send the line "unsubscribe linux-wireless" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
