Date: Fri, 29 Oct 2004 10:06:46 -0700
From: Chris Wright <chrisw@osdl.org>
To: "Andrew A." <aathan-linux-kernel-1542@cloakmail.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       roland@topspin.com, Andrew Morton <akpm@osdl.org>
Subject: Re: Consistent lock up 2.6.10-rc1-bk7 (mutex/SCHED_RR bug?)
Message-ID: <20041029100646.F14339@build.pdx.osdl.net>
References: <1099062404.13098.59.camel@localhost.localdomain> <OMEGLKPBDPDHAGCIBHHJGEMIFCAA.aathan-linux-kernel-1542@cloakmail.com>
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* Andrew A. (aathan-linux-kernel-1542@cloakmail.com) wrote:
> I suspect what is happening here is that my process is essentially in a
> 
> while(1)
> {
>   lock();
>   unlock();
> }
> 
> loop from two or mode SCHED_RR threads running at nice -15.  They seem to be unkillable.

Give yourself a shell that's SCHED_RR with a higher priority.  I've used
the small hack below to debug userspace SCHED_RR problems (newer distros
have a chrt utility to do this).

thanks,
-chris
--

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <sched.h>
#include <string.h>
#include <errno.h>

main(int argc, char *argv[])
{
	pid_t pid = 0;
	int priority = 99;
	int policy = SCHED_RR;
	struct sched_param sched;

	if (argc > 1) {
		pid = atoi(argv[1]);
		if (argc > 2) {
			priority = atoi(argv[2]);
			if (argc > 3)
				policy = atoi(argv[3]);
		}
	}

	memset(&sched, 0, sizeof(sched));
	sched.sched_priority = priority;
	if (sched_setscheduler(pid, policy, &sched) < 0) {
		printf("setscheduler: %s\n", strerror(errno));
		exit(1);
	}

	if (!pid) { /* turn this into a shell */
		argv[0] = "/bin/bash";
		argv[1] = NULL;
		execv(argv[0], argv);
	}

}
-
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