deadline scheduler BUG_ON trigger

[noman pouigt]

Folks,

I am using sched deadline in the case of audio recording over SPI to
maintain the consistency in reading the data.

However, getting this BUG_ON triggered rarely. Is it because the calculated
runtime is less than actual runtime? I only have one SCHED_DEADLINE task
in the entire system.

.sched_runtime = 5 * 1000 * 1000

<6>[  354.001991] ------------[ cut here ]------------
<2>[  354.002006] kernel BUG at
/mnt/build/workspace/fireos_main_nougat_neptune-build/VARIANT/userdebug/label/PRODUCT_BUILD_DUAL_EXEC/kernel/qcom/msm-4.4/kernel/sched/deadline.c:1035!
<6>[  354.002071] ------------[ cut here ]------------
<2>[  354.003880] kernel BUG at
/mnt/build/workspace/fireos_main_nougat_neptune-build/VARIANT/userdebug/label/PRODUCT_BUILD_DUAL_EXEC/kernel/qcom/msm-4.4/kernel/sched/deadline.c:1035!
<0>[  354.004491] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
<6>[  354.006429] Modules linked in: wlan_mt76x8_sdio(OE)
btmtksdio(OE) wlan_mt76x8_sdio_prealloc(POE)
<6>[  354.008166] CPU: 2 PID: 298 Comm: spi1 Tainted: P           OE
4.4.21+ #1
<6>[  354.008211] Hardware name: Amazon Vesta Neptune proto-3 (DT)
<6>[  354.009057] task: ffffffd936d9a580 ti: ffffffd936da8000 task.ti:
ffffffd936da8000
<6>[  354.009805] PC is at enqueue_task_dl+0x2fc/0x33c
<6>[  354.010713] LR is at enqueue_task_dl+0x2c/0x33c
<6>[  354.011297] pc : [<ffffff83c8cddf3c>] lr : [<ffffff83c8cddc6c>]
pstate: 800001c5
<6>[  354.011837] sp : ffffffd936dab9a0
<6>[  354.012781] x29: ffffffd936dab9a0 x28: ffffffd9364a3c48
<6>[  354.013814] x27: ffffffd936d9ab90 x26: 0000000000000000
<6>[  354.014477] x25: ffffffd93e0ea100 x24: 0000000000000001
<6>[  354.015138] x23: ffffffd93e0c0100 x22: ffffffd886e77090
<6>[  354.015801] x21: 0000000000000001 x20: ffffffd886e77080
<6>[  354.016462] x19: ffffffd886e77368 x18: 0000000000000044
<6>[  354.017125] x17: 0000007c4cbe7f50 x16: ffffff83c8d1b20c
<6>[  354.017786] x15: 0000000000000000 x14: 0000007c49f6e940
<6>[  354.018448] x13: 000000000019fe5a x12: 0000000001312d00
<6>[  354.019109] x11: 000000526c14c33c x10: ffffffd93e0eab40
<6>[  354.019772] x9 : ffffffd93e0eab50 x8 : 0000000000000000
<6>[  354.020434] x7 : 0000005573c60000 x6 : 0000000000000004
<6>[  354.021095] x5 : 0000005573c36000 x4 : 000000052a5b36ce
<6>[  354.021758] x3 : ffffff83c8cddc40 x2 : 0000000000000000
<6>[  354.022418] x1 : ffffffd886e77080 x0 : 0000000000000078
<6>[  354.023082]
<6>[  354.023082] PC: 0xffffff83c8cddefc:
<6>[  354.023114] defc  aa1503e0 97fffe20 f9445ae0 eb14001f 540002c0
b943a680 7100041f 5400026d
<6>[  354.024731] df1c  aa1703e0 aa1403e1 97fffeb4 1400000f 910ba001
17ffff59 7100405f 54000040
<6>[  354.025751] df3c  d4210000 b9433e80 35000100 17fffffd d4210000
17ffff72 d4210000 17ffffb6
<6>[  354.026770] df5c  f9419401 17ffffe0 a94153f3 a9425bf5 a94363f7
f94023f9 a8c67bfd d65f03c0
<6>[  354.027791]
<6>[  354.027791] LR: 0xffffff83c8cddc2c:
<6>[  354.027814] dc2c  17ffffed a94153f3 a9425bf5 a8c37bfd d65f03c0
a9ba7bfd 910003fd a90363f7
<6>[  354.029428] dc4c  aa0003f7 aa0103e0 a90153f3 f9002fa2 aa0103f4
a9025bf5 f90023f9 940045e0
<6>[  354.030449] dc6c  910ba293 f9402fa2 b40000a0 b9433e81 34000061
b9405001 37f81541 b9405280
<6>[  354.031469] dc8c  36f81540 aa1303e1 b9433680 34000040 36201642
f9417699 eb19027f 54000040
<6>[  354.032489]
<6>[  354.032489] SP: 0xffffffd936dab960:
<6>[  354.032512] b960  c8cddc6c ffffff83 36dab9a0 ffffffd9 c8cddf3c
ffffff83 800001c5 00000000
<6>[  354.034126] b980  3e0c0100 ffffffd9 39411400 ffffffd9 ffffffff
ffffffff c8cce2fc ffffff83
<6>[  354.035147] b9a0  36daba00 ffffffd9 c8cc6738 ffffff83 86e77080
ffffffd8 3e0c0100 ffffffd9
<6>[  354.036168] b9c0  00000001 00000000 86e77090 ffffffd8 3e0c0100
ffffffd9 00000001 00000000
<6>[  354.037186]
<0>[  354.037203] Process spi1 (pid: 298, stack limit = 0xffffffd936da8020)
<6>[  354.037409] Call trace:
<6>[  354.038194] Exception stack(0xffffffd936dab7d0 to 0xffffffd936dab900)
<6>[  354.038485] b7c0:
ffffffd886e77368 0000008000000000
<6>[  354.039314] b7e0: ffffffd936dab9a0 ffffff83c8cddf3c
ffffffd93844c808 0000000000000002
<6>[  354.040290] b800: ffffffd9385bf200 ffffffd93844d800
0000000000000001 0000000000000000
<6>[  354.041266] b820: 0000000000000001 ffffff83ca48a100
ffffffd93844c808 0000000000000002
<6>[  354.042242] b840: ffffff83cac06a04 0000000000000000
ffffffd936da8000 ffffffd9335a6400
<6>[  354.043219] b860: ffffffd936dab8a0 ffffff83c969ca30
0000000000000078 ffffffd886e77080
<6>[  354.044195] b880: 0000000000000000 ffffff83c8cddc40
000000052a5b36ce 0000005573c36000
<6>[  354.045173] b8a0: 0000000000000004 0000005573c60000
0000000000000000 ffffffd93e0eab50
<6>[  354.046149] b8c0: ffffffd93e0eab40 000000526c14c33c
0000000001312d00 000000000019fe5a
<6>[  354.047126] b8e0: 0000007c49f6e940 0000000000000000
ffffff83c8d1b20c 0000007c4cbe7f50
<6>[  354.048103] [<ffffff83c8cddf3c>] enqueue_task_dl+0x2fc/0x33c
<6>[  354.049078] [<ffffff83c8cc6738>] activate_task+0x74/0x124
<6>[  354.049790] [<ffffff83c8cdeabc>] push_dl_task.part.35+0x160/0x1c0
<6>[  354.050453] [<ffffff83c8cdee30>] push_dl_tasks+0x20/0x30
<6>[  354.051212] [<ffffff83c8cc4160>] __balance_callback+0x3c/0x5c
<6>[  354.051888] [<ffffff83c99cc6d8>] __schedule+0x4c4/0x770
<6>[  354.052587] [<ffffff83c99cca08>] schedule+0x84/0xa4
<6>[  354.053217] [<ffffff83c99ce91c>] __rt_mutex_slowlock+0x80/0xd8
<6>[  354.053826] [<ffffff83c99cea40>] rt_mutex_slowlock+0xcc/0x170
<6>[  354.054565] [<ffffff83c99ceb2c>] rt_mutex_lock+0x48/0x50
<6>[  354.055292] [<ffffff83c90d7664>] update_bw_adhoc+0x30/0x1d8
<6>[  354.055964] [<ffffff83c90d3294>] msm_bus_scale_update_bw+0x20/0x4c
<6>[  354.056628] [<ffffff83c9254c14>] msm_spi_clk_path_vote+0x2c/0x34
<6>[  354.057408] [<ffffff83c9254b44>] msm_spi_set_cs+0x5c/0xe4
<6>[  354.058177] [<ffffff83c924f03c>] spi_set_cs+0x50/0x5c
<6>[  354.058837] [<ffffff83c924fb4c>] spi_transfer_one_message+0x358/0x410
<6>[  354.059470] [<ffffff83c9250438>] __spi_pump_messages+0x5f8/0x624
<6>[  354.060271] [<ffffff83c9250478>] spi_pump_messages+0x14/0x1c
<6>[  354.061032] [<ffffff83c8cb9078>] kthread_worker_fn+0xb4/0x130
<6>[  354.061736] [<ffffff83c8cb8fbc>] kthread+0xdc/0xe4
<6>[  354.062440] [<ffffff83c8c845f0>] ret_from_fork+0x10/0x20
<0>[  354.063028] Code: 910ba001 17ffff59 7100405f 54000040 (d4210000)
<4>[  354.063711] ---[ end trace c62a47584ac7d903 ]---

Thanks,
variksla