lkml.org 
[lkml]   [2005]   [May]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Scheduler: SIGSTOP on multi threaded processes

I don't think the kernel handler gets a chance to do anything
because SYS-V init installs its own handler(s). There are comments
about Linux misbehavior in the code. It turns out that I was
right about SIGSTOP and SIGCONT...


Source-code header..... Current init version is 2.85 but I can't find
the source. This is 2.62
/*
* Init A System-V Init Clone.
*
* Usage: /sbin/init
* init [0123456SsQqAaBbCc]
* telinit [0123456SsQqAaBbCc]
*
* Version: @(#)init.c 2.62 29-May-1996 MvS
*
* This file is part of the sysvinit suite,
[SNIPPED...]

/*
* Linux ignores all signals sent to init when the
* SIG_DFL handler is installed. Therefore we must catch SIGTSTP
* and SIGCONT, or else they won't work....
*
* The SIGCONT handler
*/
void cont_handler()
{
got_cont = 1;
}
/*
* The SIGSTOP & SIGTSTP handler
*/
void stop_handler()
{
got_cont = 0;
while(!got_cont) pause();
got_cont = 0;
}

Now, if POSIX threads signals were implimented within the kernel,
without first purging the universe of all copies of the SYS-V init
that was distributed with early copies of RedHat and others (don't
know about current copies, a very long search failed to find the
source), then whatever you do in the kernel is wasted.

On Wed, 4 May 2005, Richard B. Johnson wrote:
> On Wed, 4 May 2005, Daniel Jacobowitz wrote:
>
>> On Wed, May 04, 2005 at 02:16:24PM -0400, Richard B. Johnson wrote:
>>> The kernel doesn't do SIGSTOP or SIGCONT. Within init, there is
>>> a SIGSTOP and SIGCONT handler. These can be inherited by others
>>> unless changed, perhaps by a 'C' runtime library. Basically,
>>> the SIGSTOP handler executes pause() until the SIGCONT signal
>>> is received.
>>>
>>> Any delay in stopping is the time necessary for the signal to
>>> be delivered. It is possible that the section of code that
>>> contains the STOP/CONT handler was paged out and needs to be
>>> paged in before the signal can be delivered.
>>>
>>> You might quicken this up by installing your own handler for
>>> SIGSTOP and SIGCONT....
>>
>> I don't know what RTOSes you've been working with recently, but none of
>> the above is true for Linux. I don't think it ever has been.
>>
>> --
>> Daniel Jacobowitz
>> CodeSourcery, LLC
>>
>
> Grab a copy of your favorite init source. SIGSTOP and SIGCONT are
> signals. They are handled by signal handlers, always have been
> on Unix and Unix clones like Linux.
>
> Cheers,
> Dick Johnson
> Penguin : Linux version 2.6.11 on an i686 machine (5537.79 BogoMips).
> Notice : All mail here is now cached for review by Dictator Bush.
> 98.36% of all statistics are fiction.
>

Cheers,
Dick Johnson
Penguin : Linux version 2.6.11 on an i686 machine (5537.79 BogoMips).
Notice : All mail here is now cached for review by Dictator Bush.
98.36% of all statistics are fiction.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-05-05 14:29    [from the cache]
©2003-2011 Jasper Spaans