On Tue, Dec 22, 2015 at 04:37:26PM +0100, Sebastian Andrzej Siewior wrote: > * Christoph Mathys | 2015-12-21 14:19:10 [+0100]: > > >While playing with 4.1.13-rt15 I stumbled across the following thread > >where Luis reports the same problem with i915 gpu: > >i915: sleeping function called from invalid context at > >intel_pipe_update_start/end > >http://www.spinics.net/lists/linux-rt-users/msg13543.html > > > >Sebastian suggested to set i915.use_mmio_flip to -1. I tried this, and > >this avoids the callstack that I've posted before > >(intel_mmio_flip_work). The BUG below is now the dominant one: > perfect. > > |BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:917 > |in_atomic(): 0, irqs_disabled(): 1, pid: 2109, name: Xorg > |hardirqs last disabled at (23744596): [<ffffffffa02bca93>] intel_pipe_update_start+0x113/0x640 [i915] > |Call Trace: > | [<ffffffff81802c33>] dump_stack+0x4a/0x61 > | [<ffffffff8108713a>] ___might_sleep+0x13a/0x200 > | [<ffffffff8180a5e4>] rt_spin_lock+0x24/0x60 > | [<ffffffff8108b47c>] ? migrate_disable+0x6c/0xe0 > | [<ffffffff810a95fb>] prepare_to_wait+0x2b/0xa0 > | [<ffffffffa02bcb48>] intel_pipe_update_start+0x1c8/0x640 [i915] > | [<ffffffff810a9ac0>] ? prepare_to_wait_event+0x130/0x130 > | [<ffffffffa02a7fc6>] intel_begin_crtc_commit+0x166/0x1e0 [i915] > | [<ffffffffa02146f2>] drm_plane_helper_commit+0x112/0x2c0 [drm_kms_helper] > | [<ffffffffa021493a>] drm_plane_helper_update+0x9a/0xf0 > > I have to admit, the i915 tries very hard to avoid running on -RT. Could > you try the s/local_irq_disable();/local_irq_disable_nort();/ patch > mentioned in the thread? > > Anyone of the i915 hackers an idea how could get the i915 working > without disabling interrupts? Is really required? It's a correctness problem - if we don't disable everything we might miss the timeframe and your screen will tear. Hence why we essentially need to run this little section of code with hard-rt semantics. There's other display chips with proper design which don't need hacks like this one here. Now of course you might want to accept a broken screen in exchange for non-broken hard rt for the things you really care about, but I'm not sure how to encode this. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
