Thank you for the explanation.
Olga
2010/7/15 Nicolas Williams <nicolas.willi...@oracle.com>:
> On Thu, Jul 15, 2010 at 12:45:54AM +0200, ольга крыжановская wrote:
>> The posix_spawn implementation in libc uses vfork. How is the POSIX
>> requirement that posix_spawn must be safe in multi threaded
>> application met if it relies on vfork which is *not* reliable in multi
>> threaded applications?
>
> vfork()/vforkx() can be used in thread-unsafe ways. Therefore they
> marked as MT-Unsafe.
>
> They can also be used in thread-safe ways. posix_spawn(3C) does use
> vforkx() in a thread-safe way. How? By not doing anything to interfere
> with the state of the parent[*] while the child is still executing in the
> borrowed address space.
>
> [*] Well, posix_spawn() does make use of stack space on the thread in
> which it was called, but unless there's code in the parent that
> makes use of uninitialized local variables, the parent won't be
> affected by this. And the function call frame of posix_spawn() may
> be modified, but not in any way that will cause any errors in the
> parent.
>
--
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