Re: [PATCH bpf-next 0/2] bpf, riscv: use BPF prog pack allocator in BPF JIT

Björn Töpel
2023-08-14T10:07:03Z

Puranjay Mohan <puranjay12@gmail.com> writes:

>> I get a hang for "test_tag", but it's not directly related to your
>> series, but rather "remote fence.i".
>
> I was seeing some stalls like this even without my series but couldn't
> debug them at that time.

Yeah, I think it's not related to your series -- it's just a good
reproducer. ;-)

>>
>> | rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
>> | rcu: 0-....: (1400 ticks this GP) idle=d5e4/1/0x4000000000000000 softirq=5542/5542 fqs=1862
>> | rcu: (detected by 1, t=5252 jiffies, g=10253, q=195 ncpus=4)
>> | Task dump for CPU 0:
>> | task:kworker/0:5 state:R running task stack:0 pid:319 ppid:2 flags:0x00000008
>> | Workqueue: events bpf_prog_free_deferred
>> | Call Trace:
>> | [<ffffffff80cbc444>] __schedule+0x2d0/0x940
>> | watchdog: BUG: soft lockup - CPU#0 stuck for 21s! [kworker/0:5:319]
>> | Modules linked in: nls_iso8859_1 drm fuse i2c_core drm_panel_orientation_quirks backlight dm_mod configfs ip_tables x_tables
>> | CPU: 0 PID: 319 Comm: kworker/0:5 Not tainted 6.5.0-rc5 #1
>> | Hardware name: riscv-virtio,qemu (DT)
>> | Workqueue: events bpf_prog_free_deferred
>> | epc : __sbi_rfence_v02_call.isra.0+0x74/0x11a
>> | ra : __sbi_rfence_v02+0xda/0x1a4
>> | epc : ffffffff8000ab4c ra : ffffffff8000accc sp : ff20000001c9bbd0
>> | gp : ffffffff82078c48 tp : ff600000888e6a40 t0 : ff20000001c9bd44
>> | t1 : 0000000000000000 t2 : 0000000000000040 s0 : ff20000001c9bbf0
>> | s1 : 0000000000000010 a0 : 0000000000000000 a1 : 0000000000000000
>> | a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000
>> | a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000052464e43
>> | s2 : 000000000000ffff s3 : 00000000ffffffff s4 : ffffffff81667528
>> | s5 : 0000000000000000 s6 : 0000000000000000 s7 : 0000000000000000
>> | s8 : 0000000000000001 s9 : 0000000000000003 s10: 0000000000000040
>> | s11: ffffffff8207d240 t3 : 000000000000000f t4 : 000000000000002a
>> | t5 : ff600000872df140 t6 : ffffffff81e26828
>> | status: 0000000200000120 badaddr: 0000000000000000 cause: 8000000000000005
>> | [<ffffffff8000ab4c>] __sbi_rfence_v02_call.isra.0+0x74/0x11a
>> | [<ffffffff8000accc>] __sbi_rfence_v02+0xda/0x1a4
>> | [<ffffffff8000a886>] sbi_remote_fence_i+0x1e/0x26
>> | [<ffffffff8000cee2>] flush_icache_all+0x1a/0x48
>> | [<ffffffff80007736>] patch_text_nosync+0x6c/0x8c
>> | [<ffffffff8000f0f8>] bpf_arch_text_invalidate+0x62/0xac
>> | [<ffffffff8016c538>] bpf_prog_pack_free+0x9c/0x1b2
>> | [<ffffffff8016c84a>] bpf_jit_binary_pack_free+0x20/0x4a
>> | [<ffffffff8000f198>] bpf_jit_free+0x56/0x9e
>> | [<ffffffff8016b43a>] bpf_prog_free_deferred+0x15a/0x182
>> | [<ffffffff800576c4>] process_one_work+0x1b6/0x3d6
>> | [<ffffffff80057d52>] worker_thread+0x84/0x378
>> | [<ffffffff8005fc2c>] kthread+0xe8/0x108
>> | [<ffffffff80003ffa>] ret_from_fork+0xe/0x20
>>
>> I'm digging into that now, and I would appreciate if you could run the
>> test_tag on VF2 or similar (I'm missing that HW).
>
> Sure, I will try to run this on the board.
> I will rebase my series(+ the patch from arm64 series) on the latest
> bpf-next tree and try to run it.

Thank you!

> Let me know if I need to add:
> + select HAVE_EFFICIENT_UNALIGNED_ACCESS if MMU && 64BIT

I usually run with that *on*, for better coverage.

Björn