Re: [9fans] fork/exec and waitpid from another proc

Re: [9fans] fork/exec and waitpid from another proc

[rob pike, esq.]

> I have a threaded process. Proc A executes new program X using fork and exec.
> After the creation proc A continues its work. Procs B and C want to know
> when/if the process X finished. As process X is not child process of B and C
> and they can't wait(2) on it. Proc A has something else to do and doesn't
> care what B and C want.
>
> Is there easy solution for this? In Unix I can use SIGCHLD for proc A to do
> something.

I am still groggy, so maybe I'm missing something, but surely you can use
either the /proc/nnn/wait file or the thread library's `wait channel'.  This
problem sounds just like the one acme has, and it solves it using a wait
channel (grep cpid /sys/src/cmd/acme/*.c or read thread(2)).  The wait
file is described in proc(3).

-rob

Re: [9fans] fork/exec and waitpid from another proc

[Latchesar Ionkov]

On Fri, May 10, 2002 at 11:27:55AM -0400, rob pike, esq. said:
> > I have a threaded process. Proc A executes new program X using fork and exec.
> > After the creation proc A continues its work. Procs B and C want to know
> > when/if the process X finished. As process X is not child process of B and C
> > and they can't wait(2) on it. Proc A has something else to do and doesn't
> > care what B and C want.
> >
> > Is there easy solution for this? In Unix I can use SIGCHLD for proc A to do
> > something.
>
> I am still groggy, so maybe I'm missing something, but surely you can use
> either the /proc/nnn/wait file or the thread library's `wait channel'.  This
> problem sounds just like the one acme has, and it solves it using a wait
> channel (grep cpid /sys/src/cmd/acme/*.c or read thread(2)).  The wait
> file is described in proc(3).

That's what I was looking for. Thanks and sorry for the stupid question.

	Lucho

Re: [9fans] fork/exec and waitpid from another proc

[Latchesar Ionkov]

On Fri, May 10, 2002 at 07:32:56AM -0400, Russ Cox said:
> > I have a threaded process. Proc A executes new program X using fork and exec.
> > After the creation proc A continues its work. Procs B and C want to know
> > when/if the process X finished. As process X is not child process of B and C
> > and they can't wait(2) on it. Proc A has something else to do and doesn't
> > care what B and C want.
>
> as you have described it, no.
>
> but you could introduce yet another proc:
>
> 	proc A forks to create Z
> 		Z forks to exec
> 		Z waits for exec'ed child
> 		Z notifies B and C however you like
>

That's what I did.:) I was just curious if there is a better way.

Thanks,
	Lucho

Re: [9fans] fork/exec and waitpid from another proc

[Russ Cox]

> I have a threaded process. Proc A executes new program X using fork and exec.
> After the creation proc A continues its work. Procs B and C want to know
> when/if the process X finished. As process X is not child process of B and C
> and they can't wait(2) on it. Proc A has something else to do and doesn't
> care what B and C want.

as you have described it, no.

but you could introduce yet another proc:

	proc A forks to create Z
		Z forks to exec
		Z waits for exec'ed child
		Z notifies B and C however you like

russ

[9fans] fork/exec and waitpid from another proc

[Latchesar Ionkov]

Hi,

I have to implement something and I am not sure I know the best way to do it.

I have a threaded process. Proc A executes new program X using fork and exec.
After the creation proc A continues its work. Procs B and C want to know
when/if the process X finished. As process X is not child process of B and C
and they can't wait(2) on it. Proc A has something else to do and doesn't
care what B and C want.

Is there easy solution for this? In Unix I can use SIGCHLD for proc A to do
something.

Thanks,

	Lucho