Date: Sat, 29 Aug 2015 13:43:36 +0200 From: Michiel Boland <boland37@xs4all.nl> To: Konstantin Belousov <kostikbel@gmail.com> Cc: Mark Martinec <Mark.Martinec+freebsd@ijs.si>, freebsd-stable@freebsd.org Subject: Re: Latest stable (r287104) bash leaves zombies on exit Message-ID: <55E19AE8.9090000@xs4all.nl> In-Reply-To: <20150828161847.GX2072@kib.kiev.ua> References: <E1ZUucG-000C5n-0C@dilbert.ingresso.co.uk> <63a84f64baf8768a551fc6464e8e9526@mailbox.ijs.si> <20150827162602.GJ2072@kib.kiev.ua> <55DF5C95.90502@xs4all.nl> <20150827201644.GO2072@kib.kiev.ua> <55DFFADB.2080003@xs4all.nl> <20150828100118.GR2072@kib.kiev.ua> <55E083CA.2050705@xs4all.nl> <20150828161847.GX2072@kib.kiev.ua>
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On 08/28/2015 18:18, Konstantin Belousov wrote:
> On Fri, Aug 28, 2015 at 05:52:42PM +0200, Michiel Boland wrote:
>> set -e
>> for a in `seq 1000`
>> do
>> echo -n "$a "
>> xterm -e ssh nonexisting
>> done
>> echo ""
>>
>> (The idea here is that 'ssh nonexisting' should do some work and then exit,
>> "xterm -e false", etc. don't appear to trigger the bug.)
>>
>> Prior to the patch, one of the xterms would hang after the counter reaches a
>> random (reasonably small) number.
>>
>> After the patch the script runs till completion.
>
> Thank you for testing. Funny detail is that your loop does not hangs for
> me, I see flapping xterms until the completion. How many cpus does your
> machine have ?
I have a Q8300 (4 cpus) - I guess the timing matters.
Do I understand correctly that the problem is that if you install a signal
handler with signal() (which is what xterm does) and pull in libthr.so somehow,
then there is no thr_sighandler inserted?
I condensed the xterm problem into a small C program. Compile in such a way that
the delay loop does not get optimized out, and link with -lpthread. Eventually,
when executed often enough, this will hang in the same fashion as xterm does.
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
static void reapchild(int sig __unused)
{
wait(NULL);
}
static void delay(void)
{
long i, n;
n = random() % 1000000;
if (n < 0) {
n = -n;
}
for (i = 0; i < n; i++)
;
}
int main()
{
int p[2];
char dummy;
srandomdev();
if (signal(SIGCHLD, reapchild) == SIG_ERR) {
perror("signal");
exit(1);
}
if (pipe(p) == -1) {
perror("pipe");
exit(1);
}
switch (fork()) {
case -1:
perror("fork");
exit(1);
case 0:
close(p[1]);
read(p[0], &dummy, 1);
_exit(0);
}
close(p[1]);
read(p[0], &dummy, 1);
delay();
exit(0);
}
>
> Below is a slightly improved version of the change, to avoid unnecessary
> relocations. Would be good to rebuild the world and confirm that you
> see no regression (the patch also affects rtld in some way).
Ok, I will try this patch later today.
Cheers,
Michiel
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