Re: [PATCH 1/1] kprobes: Deletion of an unnecessary check before the function call "module_put"

From: Masami Hiramatsu
Date: Wed Nov 19 2014 - 22:53:56 EST

(2014/11/19 16:08), SF Markus Elfring wrote:
>>> index 3995f54..f1e7d45 100644
>>> --- a/kernel/kprobes.c
>>> +++ b/kernel/kprobes.c
>>> @@ -1527,8 +1527,7 @@ int register_kprobe(struct kprobe *p)
>>> out:
>>> mutex_unlock(&kprobe_mutex);
>>> - if (probed_mod)
>>> - module_put(probed_mod);
>>> + module_put(probed_mod);
>> This is OK, but I you request a comment line over there so that
>> code reader can understand it is safe to pass a NULL pointer to
>> module_put().
> Do you want that I replace the shown null pointer check by a short
> comment which repeats an expectation for the affected function call?

No, not "want". IMHO, if try_module_get(mod) is done only when mod!=NULL,
we shouldn't call module_put(mod) when mod==NULL (even if it is possible),
because those get/put method must be used as a pair, for the better

Thank you,

Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory

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