Re: lk 3.17-rc4 blk_mq large write problems

[Jens Axboe <axboe@kernel.dk>]

On 2014-09-10 18:58, Douglas Gilbert wrote:
> On 14-09-10 11:41 AM, Christoph Hellwig wrote:
>> While it might not help with a blown stack, can you give the patch below
>> a try?  I tries to solve a problem where the timeout handler hits
>> before we've fully set up a command.  While I'd like to understand the
>> root cause of why we're hitting it as well, I'd also really to fix that
>> race. It would also be good to get a gdb listing of the exact area in
>> scsi_times_out listed in the oops.
>
> RIP: 0010:[<ffffffff8127cd2e>]  [<ffffffff8127cd2e>]
> scsi_times_out+0xe/0x2e0
>
> (gdb) disassemble scsi_times_out
> Dump of assembler code for function scsi_times_out:
>     0xffffffff8127d030 <+0>:    push   %rbp
>     0xffffffff8127d031 <+1>:    mov    $0x2007,%esi
>     0xffffffff8127d036 <+6>:    push   %rbx
>     0xffffffff8127d037 <+7>:    mov    0xf8(%rdi),%rbx
>     0xffffffff8127d03e <+14>:    mov    (%rbx),%rax
>     0xffffffff8127d041 <+17>:    mov    %rbx,%rdi
>     0xffffffff8127d044 <+20>:    mov    (%rax),%rbp
>     0xffffffff8127d047 <+23>:    callq  0xffffffff81277c70
> <scsi_log_completion>
>     0xffffffff8127d04c <+28>:    cmpl   $0xffffffff,0x154(%rbp)
>     0xffffffff8127d053 <+35>:    je     0xffffffff8127d05f
> <scsi_times_out+47>
> ...
>
> which seems to agree 'objdump -drS scsi_error.o':
>
> 00000000000028b0 <scsi_times_out>:
>      28b0:    55                       push   %rbp
>      28b1:    be 07 20 00 00           mov    $0x2007,%esi
>      28b6:    53                       push   %rbx
>      28b7:    48 8b 9f f8 00 00 00     mov    0xf8(%rdi),%rbx
>      28be:    48 8b 03                 mov    (%rbx),%rax
>      28c1:    48 89 df                 mov    %rbx,%rdi
>      28c4:    48 8b 28                 mov    (%rax),%rbp
>      28c7:    e8 00 00 00 00           callq  28cc <scsi_times_out+0x1c>
>              28c8: R_X86_64_PC32    scsi_log_completion-0x4
>      28cc:    83 bd 54 01 00 00 ff     cmpl   $0xffffffff,0x154(%rbp)

This would be more useful if you had DEBUGINFO enabled. At least it 
would save use some time :-)


-- 
Jens Axboe