linux-kernel - Re: Any lightweight way for one thread to force another thread to suspend execution?

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Date:	Sun, 22 Jun 2008 08:33:51 +0200
From:	"Bart Van Assche" <bart.vanassche@...il.com>
To:	"Eric Smith" <eric@...uhaha.com>
Cc:	linux-kernel@...r.kernel.org, "Andi Kleen" <andi@...stfloor.org>
Subject: Re: Any lightweight way for one thread to force another thread to suspend execution?

On Sun, Jun 22, 2008 at 3:55 AM, Eric Smith <eric@...uhaha.com> wrote:
> Andi wrote:
>> Any such mechanism will need a syscall, and it's unlikely that
>> any syscall will get much cheaper than a kill(SIGSTOP)
>
> But is there a way for the process sending the SIGSTOP to wait until it
> has taken effect?  I need a method to *synchronously* stop another
> thread.  That's why I thought I probably needed something more
> elaborate than SIGSTOP, though I'd like to minimize the number of
> system calls required.

Are you aware that SIGSTOP suspends all the threads in a process
instead of a single thread ? (Note: this is how the NPTL behaves. With
LinuxThreads it was possible to suspend a single thread via SIGSTOP,
but this was a violation of the POSIX standards.)

Bart.
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