Re: fork() fails if it is called recursively from a child thread.

[Eliot Moss <moss at cs dot umass dot edu>]

On 3/9/2017 6:39 AM, Takashi Yano wrote:
> Hello,
>
> I found fork() fails if it is called recursively from a child thread.
>
> Simple test case, attached (fk.c), reproduces this problem.
>
> Expected result:
> Parent 0 [22034] exit.
> Child 0 [22036] works.
> Parent 1 [22036] exit.
> Child 1 [22038] works.
> Parent 2 [22038] exit.
> Child 2 [22039] works.
> Parent 3 [22039] exit.
> Child 3 [22040] works.
> Parent 4 [22040] exit.
> Child 4 [22041] works.
>
> Result in cygwin 2.7.0:
> Child 0 [4668] works.
> Parent 0 [7188] exit.
>       0 [main] a 4668 fork: child -1 - forked process 8456 died unexpectedly, retry 0, exit code 
0xC0000142, errno 11
> fork(): Resource temporarily unavailable
>
> Strictly speaking, the test case is not safe because it calls functions
> which are not async-signal-safe from forked child process, i.e. printf()
> and perror(), in spite of multi-thread. However the same happens even
> without printf() and perror().
>
> This is the cause of which iperf 2.0.5 with option -s -D fails to start
> as daemon.
>
> Is this the known issue?

This strikes me as either BLODA (interfering software) or a need to
rebase some dll(s).  That's what I most commonly see that causes that
fork error.

Regards - Eliot Moss

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