On Sat, May 12, 2018 at 9:38 AM, Zhang Qiang <dotslash...@gmail.com> wrote:
> The -f output with more context(returning to the main thread 30617 and
> waiting for another socket connection):
>
> [pid 30670] clock_gettime(CLOCK_REALTIME, {1526142534, 664590192}) = 0
> [pid 30670] write(2, "2018/05/13 00:28:54 cmd params c"...,
> 1492018/05/13 00:28:54 cmd params create -f qcow2
> /data/kvm_img/b628579d-ae3d-41f0-887e-895204190c70/new-disk1.qcow2
> 1024M
> ) = 149
> [pid 30670] stat("/usr/local/sbin/qemu-img", 0xc42005a6b8) = -1 ENOENT
> (No such file or directory)
> [pid 30670] stat("/usr/local/bin/qemu-img", 0xc42005a788) = -1 ENOENT
> (No such file or directory)[pid 30670] stat("/usr/sbin/qemu-img",
> 0xc42005a858) = -1 ENOENT (No such file or directory)
> [pid 30670] stat("/usr/bin/qemu-img", {st_mode=S_IFREG|0755,
> st_size=815784, ...}) = 0
> [pid 30670] openat(AT_FDCWD, "/dev/null", O_RDONLY|O_CLOEXEC) = 7
> [pid 30670] pipe2([8, 9], O_CLOEXEC) = 0
> [pid 30670] pipe2([10, 11], O_CLOEXEC) = 0
> [pid 30670] close(7) = 0
> [pid 30670] close(9) = 0
> [pid 30670] close(11) = 0
> [pid 30670] close(8) = 0
> [pid 30670] close(10) = 0
> [pid 30670] write(1, "ret {\"status\":\"error\",\"error\":\"f"...,
> 79ret {"status":"error","error":"fork/exec /usr/bin/qemu-img: invalid
> argument"}
> ) = 79
> [pid 30670] write(6, "{\"status\":\"error\",\"error\":\"fork/"..., 74) = 74
> [pid 30670] write(1, "handle over, byebye\n", 20handle over, byebye
> ) = 20
> [pid 30670] epoll_ctl(5, EPOLL_CTL_DEL, 6, 0xc42004ddec) = 0[pid
> 30670] close(6) = 0
> [pid 30670] epoll_wait(5, [], 128, 0) = 0
> [pid 30670] epoll_wait(5, <unfinished ...>
> [pid 30671] <... sched_yield resumed> ) = 0
> [pid 30671] futex(0x9fe610, FUTEX_WAKE, 1) = 0
> [pid 30671] clock_gettime(CLOCK_MONOTONIC, {4411908, 247223972}) = 0
> [pid 30671] clock_gettime(CLOCK_REALTIME, {1526142534, 671270292}) = 0
> [pid 30671] pselect6(0, NULL, NULL, NULL, {0, 20000}, NULL) = 0 (Timeout)
> [pid 30671] clock_gettime(CLOCK_MONOTONIC, {4411908, 247815618}) = 0
> [pid 30671] futex(0x9fe6d8, FUTEX_WAIT, 0, {60, 0}
>
> Still seems no fork though...
Interesting. One possibility is that one of the arguments you are
passing to the process contains a NUL byte--a byte with the value 0.
That would cause this kind of error, as an argument with a NUL byte
can not be correctly passed to the kernel, which treats each argument
as ending at NUL.
Ian
> On 13 May 2018 at 00:13, Ian Lance Taylor <i...@golang.org> wrote:
>> On Fri, May 11, 2018 at 9:47 PM, Zhang Qiang <dotslash...@gmail.com> wrote:
>>>
>>> Thanks for your valuable advice on debugging.
>>>
>>> The SysProcAttr field is nil, and I can't see why it fails from the
>>> strace, seems it just found the executable and then fails without
>>> doing fork:
>>>
>>> stat("/usr/bin/qemu-img", {st_mode=S_IFREG|0755, st_size=815784, ...}) = 0
>>> write(1, "SysProcAttr: <nil>", 18SysProcAttr: <nil>) = 18
>>> openat(AT_FDCWD, "/dev/null", O_RDONLY|O_CLOEXEC) = 7
>>> pipe2([8, 9], O_CLOEXEC) = 0
>>> pipe2([10, 11], O_CLOEXEC) = 0
>>> close(7) = 0
>>> close(9) = 0
>>> close(11) = 0
>>> close(8) = 0
>>> close(10) = 0
>>> write(1, "ret {\"status\":\"error\",\"error\":\"f"..., 79ret
>>> {"status":"error","error":"fork/exec /usr/bin/qemu-img: invalid
>>> argument"}
>>
>> Thanks. That looks like the output from strace, not strace -f.
>>
>> Ian
>>
>>
>>
>>> On 12 May 2018 at 12:30, Ian Lance Taylor <i...@golang.org> wrote:
>>>> On Fri, May 11, 2018 at 8:36 PM, Tashi Lu <dotslash...@gmail.com> wrote:
>>>>>
>>>>> I faced a strange problem： os/exec always fails with `fork/exec
>>>>> /usr/bin/qemu-img: invalid argument'.
>>>>>
>>>>> Simplified code is at https://play.golang.org/p/v1APfzmS2p9. It seems this
>>>>> simplified snippet runs well without errors, but my real code is no more
>>>>> than just some variable initializations than this snippet. So I suspect
>>>>> it's
>>>>> the context's problem, but my context is too complex to simplify and put
>>>>> onto the playground. What I can think of that what might be linked to this
>>>>> error is that this function is run in a goroutine. But I did write a
>>>>> simplified goroutine version, sadly it worked well too... I had no idea
>>>>> how
>>>>> to do further debugging.
>>>>>
>>>>> And further, the executable is not to blame, it fails with the same error
>>>>> even if I substitute the executable to `ls' or anything else.
>>>>>
>>>>> Can you provide me some suggestions to the possible reason or the way to
>>>>> debug? Thanks.
>>>>
>>>> I would look first at the SysProcAttr field. Do you set that? Look
>>>> closely at the values.
>>>>
>>>> If that doesn't help, run your failing program under strace -f and
>>>> look for the failing system call.
>>>>
>>>> Ian
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