Date: Wed, 19 May 2004 21:14:58 -0700 (PDT) From: Julian Elischer <julian@elischer.org> To: Tim Robbins <tjr@freebsd.org> Cc: threads@freebsd.org Subject: Re: execve() and KSE Message-ID: <Pine.BSF.4.21.0405192113200.11004-100000@InterJet.elischer.org> In-Reply-To: <20040520015754.GA2572@cat.robbins.dropbear.id.au>
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What is supposed to happen is that all the execve should stall awaiting
all the other kernel threads to abort/suicide and then it should proceed
with the execve as per normal.
it is possible this doesn't work right.. I haven't tried ti for a LONG
time..
julian
On Thu, 20 May 2004, Tim Robbins wrote:
> What is supposed to happen when a threaded process (linked with libpthread)
> calls execve()?
>
> The program attached to this message seems to execute "true" correctly, but
> it never returns to the shell I invoked it from. ^T shows it in the state
> "running", and the system load average approaches 1.00:
>
> load: 0.15 cmd: true 726 [running] 0.00u 0.00s 0% 200k
> load: 0.56 cmd: true 726 [running] 0.00u 0.00s 0% 200k
> load: 0.91 cmd: true 726 [running] 0.00u 0.00s 0% 200k
>
> However, it's not using any CPU according to %CPU:
>
> $ ps -Haxo pid,%cpu,mwchan,state,command -p 726
> PID %CPU MWCHAN STAT COMMAND
> 726 0.0 - RL+ true
>
> The system is FreeBSD 5.2-CURRENT/amd64 with a kernel from May 9, and with
> WITNESS and INVARIANTS both turned off. I'll try updating and re-enabling
> the diagnostic options later today.
>
> Here's the code in question:
>
> #include <pthread.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <unistd.h>
>
> static pthread_cond_t cond;
>
> void *
> thrstart(void *a)
> {
>
> pthread_cond_wait(&cond, NULL);
> if (execl("/usr/bin/true", "true", NULL) < 0)
> perror("execl");
> return (NULL);
> }
>
> int
> main(int argc, char *argv[])
> {
> void *v;
> pthread_t t1;
>
> pthread_cond_init(&cond, NULL);
> pthread_create(&t1, NULL, thrstart, NULL);
> pthread_cond_broadcast(&cond);
> pthread_join(t1, &v);
>
> exit(0);
> }
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