RCU preempt cpu Stalls , able to solve it by disabling GPU

[agnel_terry]

HI ,

I have custom board with IMX6Uqad, using kernel version 4.9.123, recently we ran into rcd preempt CPU stall issue and kernel hangs, while running overnight, as part of debugging , I removed the non used Peripherals. I removed HDMI+GPu configuration, after removal , I didn't see the issue happening,

Is there an explanation , why removing GPU and HDMI , stopped the RCU preempt stalling.

Thanks and Regards

Terry

[Zhiming_Liu]

Do you have the crash log?

[agnel_terry]

Hi ,

This is the crash log.

2021-11-14T04:51:57Z xi-1B-D8-3E user.warn kernel: [973262.472947] hrtimer: interrupt took 195333 ns
2021-11-15T09:46:22Z xi-1B-D8-3E user.err kernel: [1077327.413664] INFO: rcu_preempt detected stalls on CPUs/tasks:
2021-11-15T09:46:22Z xi-1B-D8-3E user.err kernel: [1077327.419542] 1-...: (3 GPs behind) idle=ec7/140000000000000/0 softirq=76321963/76321963 fqs=998
2021-11-15T09:46:22Z xi-1B-D8-3E user.err kernel: [1077327.428506] (detected by 2, t=2103 jiffies, g=36160027, c=36160026, q=40267)
2021-11-15T09:46:22Z xi-1B-D8-3E user.info kernel: [1077327.435836] Task dump for CPU 1:
2021-11-15T09:46:22Z xi-1B-D8-3E user.info kernel: [1077327.439241] swapper/1 R running task 0 0 1 0x00000002
2021-11-15T09:46:22Z xi-1B-D8-3E user.warn kernel: [1077327.446528] [<8089b5b4>] (__schedule) from [<0003d3cd>] (0x3d3cd)
2021-11-15T09:47:25Z xi-1B-D8-3E user.err kernel: [1077390.463664] INFO: rcu_preempt detected stalls on CPUs/tasks:
2021-11-15T09:47:25Z xi-1B-D8-3E user.err kernel: [1077390.469541] 1-...: (3 GPs behind) idle=ec7/140000000000000/0 softirq=76321963/76321963 fqs=3979
2021-11-15T09:47:25Z xi-1B-D8-3E user.err kernel: [1077390.478591] (detected by 2, t=8408 jiffies, g=36160027, c=36160026, q=160474)
2021-11-15T09:47:25Z xi-1B-D8-3E user.info kernel: [1077390.486007] Task dump for CPU 1:
2021-11-15T09:47:25Z xi-1B-D8-3E user.info kernel: [1077390.489414] swapper/1 R running task 0 0 1 0x00000002
2021-11-15T09:47:25Z xi-1B-D8-3E user.warn kernel: [1077390.496702] [<8089b5b4>] (__schedule) from [<0003d3cd>] (0x3d3cd)
2021-11-15T09:48:28Z xi-1B-D8-3E user.err kernel: [1077453.513663] INFO: rcu_preempt detected stalls on CPUs/tasks:
2021-11-15T09:48:28Z xi-1B-D8-3E user.err kernel: [1077453.519541] 1-...: (3 GPs behind) idle=ec7/140000000000000/0 softirq=76321963/76321963

Thanks and Regards

Terry

[agnel_terry]

Hi,

Any info regarding the issue ?

Thanks and Regards

Terry