Messages in this thread | | | Date | Wed, 29 Dec 2010 11:39:05 +0200 | Subject | Re: [PATCH v2] staging: tidspbridge: protect dmm_map properly | From | Felipe Contreras <> |
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On Tue, Dec 28, 2010 at 2:37 PM, Ohad Ben-Cohen <ohad@wizery.com> wrote: > On Tue, Dec 28, 2010 at 2:24 PM, Felipe Contreras > <felipe.contreras@gmail.com> wrote: >> user-space crashed, not kernel-space; the code would continue to run >> and eventually release the lock. > > So you'll have to be more specific about the scenario you are describing. > > If there's a user thread that is still running the proc_*_dma() > function, and we agree that this thread keeps running until completion > and then returns to user space, what's the problem ?
The problem is if the user-space process crashes exactly in the middle of it, *before* completing. With locks there's no problem, as proc_un_map() would wait for the lock in my patch. In your patch it would not wait, just return -EBUSY.
> If that user thread will crash, drv_remove_all_resources() will clean > up all map_obj's.
Not if a proc_*_dma() is still running.
There's a very narrow timing window where this could happen, but it is there.
-- Felipe Contreras
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