Re: [Qemu-devel] [PATCH v2 39/39] raw-win32: implement native asynchronous I/O

[Jan Kiszka]

On 2012-11-21 14:38, Jan Kiszka wrote:
> On 2012-11-21 14:33, Paolo Bonzini wrote:
>> Il 21/11/2012 14:27, Jan Kiszka ha scritto:
>>>>>>> Are there any patches flying around that are supposed to resolve this?
>>>>>
>>>>> No.  Is this with aio=native or aio=threads?
>>> aio=<default> - whatever that is on win32.
>>
>> That's aio=threads, just like POSIX.  I'm curious (but not too
>> optimistic) whether aio=native fixes it.
> 
> Just tried, and it actually makes no difference.
> 
>>
>> Anyhow, do you have a reproducer that I can download?
> 
> Unfortunately, not at this point. Have to check, maybe I can trip the
> image to the bare Linux guest.

Maybe this helps:

=>0 0xf77c242e __kernel_vsyscall+0xe() in [vdso].so (0x0519df88)
  1 0xf761f10b __libc_read+0x4a() in libpthread.so.0 (0x0519df88)
  2 0x7bc78c98 in ntdll (+0x68c97) (0x0519df88)
  3 0x7bc7b0a3 in ntdll (+0x6b0a2) (0x0519e1b8)
  4 0x7bc7b195 NtWaitForMultipleObjects+0x54() in ntdll (0x0519e1e8)
  5 0x7b86de9f WaitForMultipleObjectsEx+0xee() in kernel32 (0x0519e338)
  6 0x7b86df1a WaitForMultipleObjects+0x39() in kernel32 (0x0519e368)
  7 0x0040301b aio_poll+0x16a(ctx=0x157610, blocking=<is not available>) 
[/data/qemu/aio-win32.c:178] in qemu-system-arm (0x00000001)
  8 0x004feec3 qemu_aio_wait+0x22() [/data/qemu/main-loop.c:442] in 
qemu-system-arm (0x0105bdec)
  9 0x00417166 bdrv_rw_co+0xa5(bs=0x159648, sector_num=<internal error>, 
buf="¹¸ÿ¦
                                                                                
  ", nb_sectors=0x4, is_write=true) [/data/qemu/block.c:1997] in 
qemu-system-arm (0x0105bdec)
  10 0x00495544 in qemu-system-arm (+0x95543) (0x0105bdec)
  11 0x0049592a pflash_write+0x3b9(pfl=0xd6f16e0, offset=<internal error>, 
value=0x98f7fb1d, width=0x4, be=0) [/data/qemu/hw/pflash_cfi01.c:405] in 
qemu-system-arm (0x0105bdec)
  12 0x00618a7e io_mem_write+0xed(mr=0xd6f2a48, addr=0x105bdec, val=0x98f7fb1d, 
size=0x4) [/data/qemu/memory.c:911] in qemu-system-arm (0x00000004)
  13 0x0064088c helper_stl_mmu+0x2fb(env=0x15e268, addr=0xca05bdec, 
val=0x98f7fb1d, mmu_idx=0) [/data/qemu/softmmu_template.h:231] in 
qemu-system-arm (0x3700001e)
  14 0x02136637 (0x0015e268)

It's the VCPU thread stuck in aio_poll, holding the BQL, blocking the
iothread this way as well. Is there some race that prevents we receive
the proper IO completion signal? Any states I should check?

Jan

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