On Wed, Feb 24, 2010 at 01:37:42PM +0100, Thomas Hellstrom wrote: > Jerome Glisse wrote: > >On Tue, Feb 23, 2010 at 02:05:50PM +0100, Thomas Hellstrom wrote: > >>Jerome Glisse wrote: > >>>On Mon, Feb 22, 2010 at 08:58:28PM +0100, Thomas Hellstrom wrote: > >>>>Jerome Glisse wrote: > >>>>>On Mon, Feb 22, 2010 at 06:30:24PM +0100, Thomas Hellstrom wrote: > >>>>>>Jerome Glisse wrote: > >>>>>>>Thomas i think i addressed your concern here, the ttm_bo_validate > >>>>>>>didn't needed a new argument or i did not understand what was > >>>>>>>necessary beside no_wait. In this patchset we check the value > >>>>>>>of callback in case of EBUSY (call set_need_resched) or ERESTARTSYS > >>>>>>>we return VM_FAULT_NOPAGE. > >>>>>>Well, if we from the fault callback call any function that might > >>>>>>call ttm_bo_reserve or ttm_bo_reserve_locked, we must make sure > >>>>>>that we never wait, but return -EBUSY all the way back to the > >>>>>>fault function. Such a case may be ttm_bo_validate that calls > >>>>>>ttm_bo_evict_first, or something causing a swapout... > >>>>>>ttm_bo_validate currently doesn't have that functionality, > >>>>>>because @no_wait just means don't wait for GPU. > >>>>>What do you mean by never wait ? Is this GPU wait ? or CPU wait ie don't > >>>>>use mutex or kernel code path that might sleep ? > >>>>I mean waiting while reserving a bo. (If another thread has the bo > >>>>reserved). > >>>> > >>>>>After a new review i don't think we ever wait for the GPU with the > >>>>>current > >>>>>patch and as far as i can tell we will return EBUSY or ERESTART all the > >>>>>way up. > >>>>> > >>>>>Cheers, > >>>>>Jerome > >>>>If there is *no* code path trying to reserve a bo or create a > >>>>user-space visible object from within the fault handler, it should > >>>>be ok. > >>>> > >>>>/Thomas > >>>> > >>>> > >>>Did a new review again here is the call chain : > >>>ttm_bo_move_buffer > >>> ttm_bo_mem_space > >>> ttm_bo_mem_force_space > >>> ttm_mem_evict_first > >>> ttm_bo_reserve_locked (no_wait = true) > >>Here ttm_mem_evict_fist may wait for unreserve IIRC (the -EBUSY > >>return from ttm_bo_reserve_locked) is not propagated back. > > > >The code is not straightforward but if no_wait is true the > >-EBUSY of ttm_bo_reserve_locked will be propagated back. > > The point is that we don't want to set no_wait to true, because it's > OK to wait for GPU. We want to add an extra argument > no_wait_reserve. > > /Thomas >
My patchset doesn't change the code there, no_wait will be true only if it's true as argument of ttm_bo_validate from the ttm fault callback in the driver. Cheers, Jerome ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev -- _______________________________________________ Dri-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/dri-devel
