Re: PROBLEM: Missing debug instructions when EIP is not present

[David Niklas <Hgntkwis@vfemail.net>]

Hello,

I tried categorizing under documentation, but there's only man-pages as
the component and my bug was closed as invalid.
I've updated the bugzilla link.

The file: Documentation/admin-guide/bug-hunting.rst
gives instructions on how to find the offending line of code using EIP.
My particular bug that I need to report doesn't have EIP listed -- at
least not by name. I tried to guess what EIP was in
my case "__schedule+0x29e/0x6c0" but that didn't produce any results in
gdb on my debug kernel.
I don't appear to have the referenced module type problem:
"[<ffffffff8802c8e9>] :jbd:log_wait_commit+0xa3/0xf5"

I'm totally new to kernel debugging so the documentation is really
important and I'm rather frustrated in even bothering to read it as it's
incomplete/unhelpful.

Here's the exact bug I'm trying to tackle.

[68812.480447] INFO: task CacheThread_Blo:9414 blocked for more than 480
seconds. [68812.480459]       Not tainted 4.14.184-nopreempt-AMDGPU-dav9
#1 [68812.480464] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
disables this message. [68812.480469] CacheThread_Blo D    0  9414   9082
0x00000080 [68812.480476] Call Trace:
[68812.480494]  __schedule+0x29e/0x6c0
[68812.480505]  schedule+0x32/0x80
[68812.480513]  schedule_preempt_disabled+0xa/0x10
[68812.480520]  __mutex_lock.isra.1+0x26b/0x4e0
[68812.480550]  ? do_journal_begin_r+0xbe/0x390 [reiserfs]
[68812.480570]  do_journal_begin_r+0xbe/0x390 [reiserfs]
[68812.480586]  ? __switch_to_asm+0x35/0x70
[68812.480588]  ? __switch_to_asm+0x41/0x70
[68812.480590]  ? __switch_to_asm+0x35/0x70
[68812.480592]  ? __switch_to_asm+0x41/0x70
[68812.480593]  ? __switch_to_asm+0x35/0x70
[68812.480595]  ? __switch_to_asm+0x41/0x70
[68812.480597]  ? __switch_to_asm+0x35/0x70
[68812.480601]  journal_begin+0x80/0x140 [reiserfs]
[68812.480606]  reiserfs_dirty_inode+0x3d/0xa0 [reiserfs]
[68812.480609]  ? __switch_to+0x1ee/0x3f0
[68812.480610]  ? __switch_to+0x1ee/0x3f0
[68812.480612]  __mark_inode_dirty+0x163/0x350
[68812.480615]  generic_update_time+0x79/0xc0
[68812.480617]  ? current_time+0x38/0x70
[68812.480619]  file_update_time+0xbe/0x110
[68812.480622]  __generic_file_write_iter+0x99/0x1b0
[68812.480624]  generic_file_write_iter+0xe2/0x1c0
[68812.480626]  __vfs_write+0x102/0x180
[68812.480628]  vfs_write+0xb0/0x190
[68812.480630]  SyS_pwrite64+0x90/0xb0
[68812.480632]  do_syscall_64+0x6e/0x110
[68812.480634]  entry_SYSCALL_64_after_hwframe+0x41/0xa6
[68812.480637] RIP: 0033:0x7f8a92976983
[68812.480638] RSP: 002b:00007f8a779e1630 EFLAGS: 00000293 ORIG_RAX:
0000000000000012 [68812.480640] RAX: ffffffffffffffda RBX:
00007f8a779e1640 RCX: 00007f8a92976983 [68812.480641] RDX:
0000000000000128 RSI: 000001790ddf3c00 RDI: 0000000000000040
[68812.480642] RBP: 00007f8a779e16f0 R08: 00007f8a779e1558 R09:
0000000000000001 [68812.480643] R10: 0000000000002000 R11:
0000000000000293 R12: 0000000000002000 [68812.480644] R13:
000001790a6b8dd0 R14: 000001790ddf3c00 R15: 0000000000000128
[68812.480647] INFO: task ThreadPoolSingl:9908 blocked for more than 480
seconds.

4.14.184

https://bugzilla.kernel.org/show_bug.cgi?id=208777

Thanks,
David