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Date: Tue, 11 Feb 2003 02:10:54 -0800
From: Andrew Morton <akpm@digeo.com>
To: Con Kolivas <ckolivas@yahoo.com.au>
Cc: linux-kernel@vger.kernel.org, Linus Torvalds <torvalds@transmeta.com>,
       Roland McGrath <roland@redhat.com>
Subject: Re: [BENCHMARK] 2.5.60 with contest
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Con Kolivas <ckolivas@yahoo.com.au> wrote:
>
> interestingly dbench_load wouldnt give me a number because dbench never
> quite started - a whole swag of processes visible but not doing anything

Signal problems...

What dbench is doing is:

- Install a SIGCONT handler
- fork N times, children drop into a pause()
- parent does kill(0, SIGCONT);

It appears that the SIGCONT is not causing the children to drop out of the
pause().

Changing it to SIGINT makes it work.

The tarball is at http://samba.org/ftp/tridge/dbench/dbench-2.0.tar.gz

Here's the relevant snippet:

static double create_procs(int nprocs, void (*fn)(struct child_struct * ))
{
	int i, status;
	int synccount;

	signal(SIGCONT, sigcont);

	start_timer();

	synccount = 0;

	if (nprocs < 1) {
		fprintf(stderr,
			"create %d procs?  you must be kidding.\n",
			nprocs);
		return 1;
	}

	children = shm_setup(sizeof(struct child_struct)*nprocs);
	if (!children) {
		printf("Failed to setup shared memory\n");
		return end_timer();
	}

	memset(children, 0, sizeof(*children)*nprocs);

	for (i=0;i<nprocs;i++) {
		children[i].id = i;
		children[i].nprocs = nprocs;
	}

	for (i=0;i<nprocs;i++) {
		if (fork() == 0) {
			setbuffer(stdout, NULL, 0);
			nb_setup(&children[i]);
			children[i].status = getpid();
			pause();
			fn(&children[i]);
			_exit(0);
		}
	}

	do {
		synccount = 0;
		for (i=0;i<nprocs;i++) {
			if (children[i].status) synccount++;
		}
		if (synccount == nprocs) break;
		sleep(1);
	} while (end_timer() < 30);

	if (synccount != nprocs) {
		printf("FAILED TO START %d CLIENTS (started %d)\n", nprocs, synccount);
		return end_timer();
	}

	start_timer();
	kill(0, SIGCONT);


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