On Wed, 2013-05-22 at 15:58 +0400, Roman Gushchin wrote: > +/* > + * Same as ACCESS_ONCE(), but used for accessing field of a structure. > + * The main goal is preventing compiler to store &ptr->field in a register.
But &ptr->field is a constant during the whole duration of udp4_lib_lookup2() and could be in a register, in my case field is at offset 0, and ptr is a parameter (so could be in a 'register') The bug you found is that compiler caches the indirection (ptr->field) into a register, not that compiler stores &ptr->field into a register. > + */ > +#define ACCESS_FIELD_ONCE(PTR, FIELD) (((volatile typeof(*PTR) *)PTR)->FIELD) > + Here we force the compiler to consider ptr as volatile, but semantically it is not required in rcu_dereference(ptr->field) We want field to be reloaded, not ptr. So yes, the patch appears to fix the bug, but it sounds not logical to me. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
