[Intel-gfx] [PATCH 1/4] drm/i915: Only call finish_reset after a prepare_reset

[Chris Wilson]

Quoting Maarten Lankhorst (2018-04-05 12:10:23)
> Op 05-04-18 om 13:02 schreef Chris Wilson:
> > If we skip the intel_prepare_reset(), we should also skip the
> > intel_display_reset(). If we we use a flag set by intel_prepare_reset()
> > then we do not have to second guess based on external user controlled
> > state whether or not the prepare was called before deciding to finish
> > it after the reset. igt/gem_eio is one such example that may tweak
> > i915.reset faster than the code is expecting, leading to
> >
> > [  190.233528] =====================================
> > [  190.233534] WARNING: bad unlock balance detected!
> > [  190.233540] 4.16.0-rc7-g335ef9849310-drmtip_10+ #1 Tainted: G     U
> > [  190.233547] -------------------------------------
> > [  190.233553] gem_eio/1348 is trying to release lock (crtc_ww_class_acquire) at:
> > [  190.233569] [<ffffffff895c7810>] drm_modeset_acquire_fini+0x0/0x60
> > [  190.233575] but there are no more locks to release!
> > [  190.233580]
> >                other info that might help us debug this:
> > [  190.233588] 3 locks held by gem_eio/1348:
> > [  190.233592]  #0:  (&f->f_pos_lock){+.+.}, at: [<00000000ab90c784>] __fdget_pos+0x3a/0x50
> > [  190.233607]  #1:  (sb_writers#11){.+.+}, at: [<00000000e1529265>] vfs_write+0x188/0x1a0
> > [  190.233622]  #2:  (&attr->mutex){+.+.}, at: [<0000000011f40afe>] simple_attr_write+0x36/0xd0
> > [  190.233635]
> >                stack backtrace:
> > [  190.233644] CPU: 0 PID: 1348 Comm: gem_eio Tainted: G     U           4.16.0-rc7-g335ef9849310-drmtip_10+ #1
> > [  190.233655] Hardware name: Dell Inc.                 OptiPlex GX280               /0G8310, BIOS A04 02/09/2005
> > [  190.233664] Call Trace:
> > [  190.233674]  dump_stack+0x67/0x95
> > [  190.233682]  ? drm_modeset_backoff+0x1b0/0x1b0
> > [  190.233690]  print_unlock_imbalance_bug+0xd2/0xe0
> > [  190.233698]  ? drm_modeset_backoff+0x1b0/0x1b0
> > [  190.233704]  lock_release+0x23e/0x300
> > [  190.233712]  drm_modeset_acquire_fini+0x16/0x60
> > [  190.233835]  intel_finish_reset+0x72/0x160 [i915]
> > [  190.233894]  i915_reset_device+0x1e9/0x240 [i915]
> > [  190.233953]  ? __intel_get_crtc_scanline+0x1c0/0x1c0 [i915]
> > [  190.233962]  ? work_on_cpu_safe+0x50/0x50
> > [  190.234020]  i915_handle_error+0x1f2/0x470 [i915]
> > [  190.234031]  ? __might_fault+0x39/0x90
> > [  190.234037]  ? __might_fault+0x39/0x90
> > [  190.234099]  i915_wedged_set+0x7f/0xc0 [i915]
> > [  190.234107]  simple_attr_write+0xb0/0xd0
> > [  190.234117]  full_proxy_write+0x51/0x80
> > [  190.234125]  __vfs_write+0x21/0x140
> > [  190.234133]  ? rcu_read_lock_sched_held+0x6f/0x80
> > [  190.234140]  ? rcu_sync_lockdep_assert+0x29/0x50
> > [  190.234147]  ? __sb_start_write+0x152/0x1f0
> > [  190.234152]  ? __sb_start_write+0x168/0x1f0
> > [  190.234159]  vfs_write+0xbd/0x1a0
> > [  190.234166]  SyS_write+0x40/0xa0
> > [  190.234173]  ? do_syscall_64+0x19/0x1b0
> > [  190.234180]  do_syscall_64+0x6b/0x1b0
> > [  190.234188]  entry_SYSCALL_64_after_hwframe+0x42/0xb7
> > [  190.234196] RIP: 0033:0x7f84c1b392b7
> > [  190.234201] RSP: 002b:00007f84b6755b00 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
> > [  190.234211] RAX: ffffffffffffffda RBX: 0000000000000046 RCX: 00007f84c1b392b7
> > [  190.234218] RDX: 0000000000000002 RSI: 000055ec20abc8d6 RDI: 0000000000000046
> > [  190.234225] RBP: 000055ec20abc8d6 R08: 0000000000000000 R09: 0000000000000000
> > [  190.234231] R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000002
> > [  190.234238] R13: 0000000000000000 R14: 00007f84b0000b20 R15: 000055ec20ce4eb8
> >
> > Testcase: igt/gem_eio
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
[snip]
> Reviewed-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>

Thanks for the review, applied this patch and hopefully we only need
this one by itself to clear up the warnings from the shards on these old
machine.
-Chris