wait4(), waitid(), and exit()

Lego supports wait4() and waitid() syscalls, and they are compatible with Linux programs. These two syscalls rely on exit_notify() function when a thread exit(). Basically, when a thread exit, it will notify its parent, and reparent³ its children if necessary.

Facts in Lego:

• Lego does not have process group and session² concept. Each process is within its own process group and session.
• This implies Lego will not have Orphaned Process Group¹ when a process exit.
• Orphan process³ is adopted by init process (pid 1) if its father is a single-thread process, otherwise it will be adopted by other thread within its father’s process. This is performed by function forget_original_parent().
• wait, signal, exec, fork are close related.

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Yizhou Shan
Created: Mar 8, 2018
Last Updated: Mar 10, 2018

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1. Orphaned Process Groups ↩

2. Process Group ↩

3. Orphan Process ↩↩

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Last update: March 12, 2018

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