[PATCH] drm/i915: Make vm eviction uninterruptible

Ben Widawsky
2014-04-05T20:08:05Z

Our current code cannot handle a failure to evict well. You'll get at
the very least the following splat, but usually a lot worse fallout after:

[ 134.819441] ------------[ cut here ]------------
[ 134.819467] WARNING: CPU: 3 PID: 442 at drivers/gpu/drm/i915/i915_gem_evict.c:230 i915_gem_evict_vm+0x8a/0x1c0 [i915]()
[ 134.819471] Modules linked in: i915 drm_kms_helper drm intel_gtt agpgart i2c_algo_bit ext4 crc16 mbcache jbd2 x86_pkg_temp_thermal coretemp kvm_intel kvm crc32c_intel ghash_clmulni_intel aesni_intel aes_x86_64 lrw iTCO_wdt gf128mul iTCO_vendor_support glue_helper ablk_helper cryptd microcode serio_raw i2c_i801 fan thermal battery e1000e acpi_cpufreq evdev ptp ac acpi_pad pps_core processor lpc_ich mfd_core snd_seq_dummy snd_seq_oss snd_seq_midi_event snd_seq snd_seq_device snd_timer snd soundcore sd_mod crc_t10dif crct10dif_common ahci libahci libata ehci_pci ehci_hcd usbcore scsi_mod usb_common
[ 134.819565] CPU: 3 PID: 442 Comm: glxgears Not tainted 3.14.0-BEN+ #480
[ 134.819568] Hardware name: Intel Corporation Broadwell Client platform/WhiteTip Mountain 1, BIOS BDW-E1R1.86C.0063.R01.1402110503 02/11/2014
[ 134.819571] 0000000000000009 ffff88009b10fa80 ffffffff8159e6a5 0000000000000000
[ 134.819577] ffff88009b10fab8 ffffffff8104895d ffff880145c353c0 ffff880145f400f8
[ 134.819584] 0000000000000000 ffff8800a274d300 ffff88009b10fb78 ffff88009b10fac8
[ 134.819590] Call Trace:
[ 134.819599] [<ffffffff8159e6a5>] dump_stack+0x4e/0x7a
[ 134.819607] [<ffffffff8104895d>] warn_slowpath_common+0x7d/0xa0
[ 134.819635] [<ffffffff81048a3a>] warn_slowpath_null+0x1a/0x20
[ 134.819656] [<ffffffffa050c82a>] i915_gem_evict_vm+0x8a/0x1c0 [i915]
[ 134.819677] [<ffffffffa050a26b>] ppgtt_release+0x17b/0x1e0 [i915]
[ 134.819693] [<ffffffffa050a34d>] i915_gem_context_free+0x7d/0x180 [i915]
[ 134.819707] [<ffffffffa050a48c>] context_idr_cleanup+0x3c/0x40 [i915]
[ 134.819715] [<ffffffff81332d14>] idr_for_each+0x104/0x1a0
[ 134.819730] [<ffffffffa050a450>] ? i915_gem_context_free+0x180/0x180 [i915]
[ 134.819735] [<ffffffff815a27fc>] ? mutex_lock_nested+0x28c/0x3d0
[ 134.819761] [<ffffffffa057da75>] ? i915_driver_preclose+0x25/0x50 [i915]
[ 134.819778] [<ffffffffa050b715>] i915_gem_context_close+0x35/0xa0 [i915]
[ 134.819802] [<ffffffffa057da80>] i915_driver_preclose+0x30/0x50 [i915]
[ 134.819816] [<ffffffffa03e6a7d>] drm_release+0x5d/0x5f0 [drm]
[ 134.819822] [<ffffffff811aae3a>] __fput+0xea/0x240
[ 134.819827] [<ffffffff811aafde>] ____fput+0xe/0x10
[ 134.819832] [<ffffffff810701bc>] task_work_run+0xac/0xe0
[ 134.819837] [<ffffffff8104b82f>] do_exit+0x2cf/0xcf0
[ 134.819844] [<ffffffff815a5dac>] ? _raw_spin_unlock_irq+0x2c/0x60
[ 134.819849] [<ffffffff8104c2dc>] do_group_exit+0x4c/0xc0
[ 134.819855] [<ffffffff8105ef11>] get_signal_to_deliver+0x2d1/0x920
[ 134.819861] [<ffffffff81002408>] do_signal+0x48/0x620
[ 134.819867] [<ffffffff811aa0d9>] ? do_readv_writev+0x169/0x220
[ 134.819873] [<ffffffff8109e33d>] ? trace_hardirqs_on_caller+0xfd/0x1c0
[ 134.819879] [<ffffffff811c9b9d>] ? __fget_light+0x13d/0x160
[ 134.819886] [<ffffffff815a744c>] ? sysret_signal+0x5/0x47
[ 134.819892] [<ffffffff81002a45>] do_notify_resume+0x65/0x80
[ 134.819897] [<ffffffff815a76da>] int_signal+0x12/0x17
[ 134.819901] ---[ end trace dbf4da2122c3d683 ]---

At first I was going to call this a bandage to the problem. However,
upon further thought, I rather like the idea of making evictions atomic,
and less prone to failure anyway. The reason it can still somewhat be
considered a band-aid however is GPU hangs. It would be nice if we had
some way to interrupt the process when the GPU is hung. I'll leave it
for a follow patch though.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
---
drivers/gpu/drm/i915/i915_gem_evict.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_evict.c b/drivers/gpu/drm/i915/i915_gem_evict.c
index 75fca63..91da738 100644
--- a/drivers/gpu/drm/i915/i915_gem_evict.c
+++ b/drivers/gpu/drm/i915/i915_gem_evict.c
@@ -225,10 +225,17 @@ int i915_gem_evict_vm(struct i915_address_space *vm, bool do_idle)
i915_gem_retire_requests(vm->dev);
}

- list_for_each_entry_safe(vma, next, &vm->inactive_list, mm_list)
+ list_for_each_entry_safe(vma, next, &vm->inactive_list, mm_list) {
+ struct drm_i915_private *dev_priv = vm->dev->dev_private;
+ bool old_intr = dev_priv->mm.interruptible;
+ dev_priv->mm.interruptible = false;
+
if (vma->pin_count == 0)
WARN_ON(i915_vma_unbind(vma));

+ dev_priv->mm.interruptible = old_intr;
+ }
+
return 0;
}

--
1.9.1