On Tue, Nov 24, 2015 at 10:14:20PM +0000, Chris Wilson wrote: > On Tue, Nov 24, 2015 at 09:49:58PM +0100, Thomas Hellstrom wrote: > > Hi, Chris, > > > > With your new (well sort of) implementation of drm_read() it looks to me > > like a drm_read() to a paged out > > memory area will always fail with -EFAULT. From what I can tell, there's > > nothing there to generate a page-fault to get the destination paged back > > into memory? > > True. Whoops. Ok, I've added a test case (igt/drm_read/fault-buffer) that forces a pagefault here by using a dumb bo as the destination buffer. (At least on i915, we do not do any prefaulting inside the mmap routine.) That demonstrates that __copy_to_user_inatomic() itself does not disable pagefaults (i.e. it does not call pagefault_disable) and hence why we don't always immediately generate EFAULT. That leaves us with the issue that the fault handler may still deadlock on the dev->event_lock, so it still needs to be fixed. -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
