On Tue, Dec 28, 2010 at 12:36 PM, Felipe Contreras <felipe.contreras@xxxxxxxxx> wrote: >> You can never really tell who is using the kernel (or will be using >> this kernel version), how and under which workload. > > No, but it's better to address real issues rather than hypothetical. Right. and both patches do that. one adds locks, and one doesn't. > However, as I sad, everybody is using proc_map() and proc_un_map() > which take a lock, and there are no complaints. I didn't complain about that; I didn't like you adding locks to the DMA API. > Ok, can I get your Ack? Frankly, I don't like the locks you are adding. But as I said, I wouldn't resist them as long as it's temporary. > Then why did you add that check for is_map_obj_used(), and then return > -EBUSY? If that can happen, then it can happen when the application is > crashing; user-space crashes while kernel-space is in the middle of a > proc_*_dma() operation. I still don't know how exactly you triggered the bug: is gst-dsp multithreaded ? and one of its threads invoked proc_un_map() while another thread called proc_begin_dma() ? Anyhow, a thread that is calling proc_*_dma() will both increase the reference count and decrease it back before going back to user space. Otherwise your patch would be problematic as well - who will unlock the mutex you take in proc_*_dma() ? >>> Sure, but I see this as a broader effort to have finer locking, part of >>> this should be to remove the already existing proc_lock. >> >> Having bad locking is not an excuse for adding more. > > No, but not being a permanent solution is not an excuse for not fixing > a kernel panic right away. Right. But we have a fix that doesn't add any additional locking... I don't see why it can't be taken now, but as I said, I wouldn't resist staging it for the next cycle. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
