Messages in this thread | | | Date | Wed, 21 Jun 2006 23:01:05 +1000 | From | Peter Williams <> | Subject | Re: [Lse-tech] [PATCH 09/11] Task watchers: Add support for per-task watchers |
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Peter Williams wrote: > Andrew Morton wrote: >> On Tue, 20 Jun 2006 18:20:48 -0700 >> Matt Helsley <matthltc@us.ibm.com> wrote: >> >>>>>>> +static inline int notify_per_task_watchers(unsigned int val, >>>>>>> + struct task_struct *task) >>>>>>> +{ >>>>>>> + if (get_watch_event(val) != WATCH_TASK_INIT) >>>>>>> + return raw_notifier_call_chain(&task->notify, val, task); >>>>>>> + RAW_INIT_NOTIFIER_HEAD(&task->notify); >>>>>>> + if (task->real_parent) >>>>>>> + return raw_notifier_call_chain(&task->real_parent->notify, >>>>>>> + val, task); >>>>>>> +} >>>>>> It's possible for this task to exit without returning a result. >>>>> Assuming you meant s/task/function/: >>>>> >>>>> In the common case this will return a result because most tasks >>>>> have a >>>>> real parent. The only exception should be the init task. However, the >>>>> init task does not "fork" from another task so this function will >>>>> never >>>>> get called with WATCH_TASK_INIT and the init task. >>>>> >>>>> This means that if one wants to use per-task watchers to >>>>> associate data >>>>> and a function call with *every* task, special care will need to be >>>>> taken to register with the init task. >>>> no...... >>> I've been looking through the source and, from what I can see, >>> the end >>> of the function is not reachable. I think I need to add: >>> >>> notify_watchers(WATCH_TASK_INIT, &init_task); >>> >>> to make this into an applicable warning. >> >> If the end of the function isn't reachable then the >> `if (task->real_parent)' can simply be removed. > > Perhaps with a comment to say that it's safe (and why) to dereference > task->real_parent to help code reviewers?
Now that I understand this code better, I'm at a loss to understand why you're calling the parent with the notifier. I can't think of any circumstances where this would be useful.
Peter -- Peter Williams pwil3058@bigpond.net.au
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