Messages in this thread | | | Subject | Re: try module get code understanding | From | Valdis.Kletnieks@vt ... | Date | Thu, 27 Sep 2007 02:14:34 -0400 |
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On Thu, 27 Sep 2007 05:19:06 -0000, Shreyansh Jain said:
> ----- > static inline int try_module_get(struct module *module){ > int ret = 1; <--- error case when !module > if (module) { > unsigned int cpu = get_cpu(); > if (likely(module_is_live(module))) > local_inc(&module->ref[cpu].count); > else > ret = 0; <--- error case > put_cpu(); > } > return ret; <---- > }
> 1. In case the module pointer passed is invalid (NULL) this function would > return 1 (error case) > 2. In case the module pointer is OK, and module is currently not being removed, > reference count would be incremented and 1 returned (non error case) > 3. In case the module pointer is OK, and module reference count can NOT be > increased, 0 would be returned (error case). > > As you can observe from above points, 0 and 1 are returned for error cases. I am > a little confused and wondering if there is something which I am missing in this > code??.
Go look at the call sites for this function - I bet that most of them, if they check the return code at all, only check for zero or nonzero, because they only *care* about the case that returns zero. Since they already know they're not passing a NULL pointer, they don't worry about that case returning a 1. So there's only two realistic returns - either the module is live or it isn't. [unhandled content-type:application/pgp-signature] | |