Re: waitpid on a thread.

[Sharath <sharath_75@yahoo.com>]

Amit,

the threading library on Linux is a a bit different
from the normal 'threads'.

Strictly threads are not children of a process as a
fork(...) does. When a child of a process terminated,
the parent process gets a SIGCHLD. However when a
thread terminates is doesn't.

The way threading is implemented on linux (where every
thread is represented as a child) is a quirk.

The thread (though it appears as a child) is in fact
*not a true cild* of the process hence waitpid(...)
rightly returns. You shouldn't be using waitpid(...)
to wait on a thread rather use pthread_join(...)  but
then you need to pass on the pthread_t that you got
when you created it.

-Sharath

--- Amit Nadgar <vangough_spinlock@yahoo.com> wrote:
> hi,
>   I am trying to do a ptrace on a thread. Ptrace
> returns successfully. However when I do a waitpid
> where pid I pass is the pid of the thread I wait
> returns immediately. When I use the same program on
> a
> unthreaded process it works fine. 
>   Can anybody help me with this?
>              
> 
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