On 07/09/2013 09:17 AM, Florian Kelbert wrote:
>
>
> On 08.07.2013 10:00, Denys Vlasenko wrote:
>> On 07/05/2013 01:18 PM, Florian Kelbert wrote:
>>> Hi all,
>>>
>>> while trying to strace nginx (http://nginx.org/), using strace -f, I
>>> realized that strace fails to trace a forked child process.
>>
>> Which version of strace and kernel do you have?
>
> I compiled strace 4.8 from the sources using ./configure && make; using
> Ubuntu 13.04, kernel 3.8.0-25
>
>>
>> Can you show the same event with -d option added to strace
>> command line? (the debug output goes to stderr, not -o LOGFILE).
>>
>
> ./strace -f -d ~/nginx/sbin/nginx
>
> http://pastebin.com/ZwHXHrWa
>
> Process 7428 is born in line 518 and survives the subsequent exit_group() by
> process 7427, as the output of ps shows:
The log shows that exit_group(0) is indeed called immediately after clone(),
making "strace exited too early to see the child" theory feasible.
Can you test this theory by replacing
while (nprocs != 0)
with
while (1)
in strace.c in function trace()?
The exit from trace loop will then happen when we receive ECHILD.
In my testing it worked.
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