What happens when a parent process is terminated?
A terminated process is said to be a zombie or defunct until the parent does wait on the child. When a process terminates all of the memory and resources associated with it are deallocated so they can be used by other processes.
What is the purpose of vfork()?
vfork() is a special case of clone(2). It is used to create new processes without copying the page tables of the parent process. It may be useful in performance-sensitive applications where a child is created which then immediately issues an execve(2).
Is vfork deprecated?
The problem is that it is less safe and the man page says vfork is likely to become deprecated in the future. A safer and more portable solution may be to look at the posix_spawn function, which is higher level and offers more options. It safely uses vfork when possible, depending on the options you pass it.
What happens to threads when process terminates?
Terminating a process has the following results: Any remaining threads in the process are marked for termination. Any resources allocated by the process are freed. All kernel objects are closed.
What happens when Vfork is called in multithreaded process?
When vfork () is called in a multithreaded process, only the calling thread is suspended until the child terminates or executes a new program. This means that the child is sharing an address space with other running code.
What’s the difference between vfork ( ) and exec ( )?
In particular, the child process must not return from the function containing the vfork () call, and it must not call exit () (if it needs to exit, it should use _exit (); actually, this is also true for the child of a normal fork ()). Exec : The exec call is a way to basically replace the entire current process with a new program.
Which is an example of the dangers of vfork?
As an example of the dangers, suppose that a multithreaded program running as root creates a child using vfork (). After the vfork (), a thread in the parent process drops the process to an unprivileged user in order to run some untrusted code (e.g., perhaps via plug-in opened with dlopen (3) ).
When to use vfork when memory is constrained?
* On systems where memory is constrained, vfork () avoids the need to temporarily commit memory (see the description of /proc/sys/vm/overcommit_memory in proc (5)) in order to execute a new program. (This can be especially beneficial where a large parent process wishes to execute a small helper program in a child process.)