[PATCH v3 2/2] posix: Use posix_spawn on system

[Florian Weimer]

* Adhemerval Zanella:

> On 29/11/2018 15:37, Florian Weimer wrote:
>> * Adhemerval Zanella:
>> 
>>> +/* We have to and actually can handle cancelable system().  The big
>>> +   problem: we have to kill the child process if necessary.  To do
>>> +   this a cleanup handler has to be registered and it has to be able
>>> +   to find the PID of the child.  The main problem is to reliable have
>>> +   the PID when needed.  It is not necessary for the parent thread to
>>> +   return.  It might still be in the kernel when the cancellation
>>> +   request comes.  Therefore we have to use the clone() calls ability
>>> +   to have the kernel write the PID into the user-level variable.  */
>> 
>> This comment does not look relevant to me anymore.
>
> I think it still worth to mention glibc system aims to be thread-safe,
> which requires restore the signal dispositions for SIGINT and SIGQUIT 
> correctly and to deal with cancellation by terminating the child process.

> +/* This system implementation aims to be thread-safe, which requires restore
> +   the signal dispositions for SIGINT and SIGQUIT correctly and to deal with
> +   cancellation by terminating the child process.  */

I don't think you restore SIGINT and SIGQUIT correctly for concurrent
system calls.  This is what the ADD_REF code in the old version
attempted to do.

Thnaks,
Florian