Hi Steve, Joel

Sorry to bother you.

On my slow arm64 vm, inserting and removing preemptirq_delay_test module in loops triggers kernel panic sometimes.

Reproduce steps: Do the following steps in loops(more than 10 times): [root@CentOS81-aarch64 ]# modprobe preemptirq_delay_test test_mode=preempt delay=500000; rmmod preemptirq_delay_test

Call Trace: ------------------------------------------------------------------- [172413.750294] Unable to handle kernel paging request at virtual address fffffe0009010280 [172413.790511] Mem abort info: [172413.791129] ESR = 0x86000007 [172413.791656] EC = 0x21: IABT (current EL), IL = 32 bits [172413.792322] SET = 0, FnV = 0 [172413.792793] EA = 0, S1PTW = 0 [172413.794082] swapper pgtable: 64k pages, 42-bit VAs, pgdp=0000000040ef0000 [172413.794556] [fffffe0009010280] pgd=00000000bfff0003, pud=00000000bfff0003, pmd=00000000bfff0003, pte=0000000000000000 [172413.795690] Internal error: Oops: 86000007 [#1] PREEMPT SMP [172413.796285] Modules linked in: sunrpc vfat fat ext4 mbcache jbd2 crct10dif_ce ghash_ce sha2_ce sha256_arm64 sha1_ce ip_tables xfs libcrc32c virtio_net net_failover failover virtio_blk virtio_mmio [last unloaded: preemptirq_delay_test] [172413.797797] CPU: 1 PID: 15750 Comm: preempt_test Not tainted 5.6.0-rc7 #17 [172413.798275] Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015 [172413.799049] pstate: 40000005 (nZcv daif -PAN -UAO) [172413.799934] pc : 0xfffffe0009010280 [172413.800230] lr : 0xfffffe0009010280 [172413.800497] sp : fffffe001390fe00 [172413.800799] x29: fffffe001390fe00 x28: 0000000000000000 [172413.801263] x27: 0000000000000000 x26: fffffe0009010000 [172413.801726] x25: 0000000000000000 x24: fffffe00114a3670 [172413.802164] x23: fffffe0010d1d150 x22: fffffe0016b2f9e8 [172413.802635] x21: 0000000000000000 x20: fffffe0009030008 [172413.803191] x19: fffffe0009030000 x18: 0000000000000000 [172413.803672] x17: 0000000000000000 x16: 0000000000000000 [172413.804118] x15: 0000000000000000 x14: 0000000000000000 [172413.804558] x13: 0000000000000000 x12: 0000000000000000 [172413.805013] x11: 0000000000000000 x10: 0000000000000d50 [172413.805441] x9 : fffffe001390fd10 x8 : fffffc00762930b0 [172413.805944] x7 : 00000000fa83b2da x6 : 0000000000000000 [172413.806455] x5 : fffffe001127c000 x4 : fffffe006ed00000 [172413.806874] x3 : fffffe001127cf50 x2 : 0000000000000002 [172413.807312] x1 : 0000000000000000 x0 : 0000000000000228 [172413.807869] Call trace: [172413.808146] 0xfffffe0009010280 [172413.808436] 0xfffffe0009010294 [172413.808723] 0xfffffe0009010050 [172413.809519] kthread+0x110/0x118 [172413.809734] ret_from_fork+0x10/0x18 [172413.810338] Code: bad PC value [172413.811203] ---[ end trace 69c688402fdc8bb1 ]--- [172413.811670] Kernel panic - not syncing: Fatal exception [172413.812108] SMP: stopping secondary CPUs [172413.812733] Kernel Offset: disabled [172413.813043] CPU features: 0x10002,20006082 [172413.813387] Memory Limit: none [172413.813849] ---[ end Kernel panic - not syncing: Fatal exception]--- -------------------------------------------------------------------

Do you have any suggestion about the issue.

Thanks, Xiao Yang