threads/119920: fork broken in libpthread

[Landon Fuller]

On Jan 24, 2008, at 07:08, Daniel Eischen wrote:

> On Thu, 24 Jan 2008, Julian Elischer wrote:
>
>> Gary Stanley wrote:
>>> The following reply was made to PR threads/119920; it has been  
>>> noted by
>>> GNATS.
>>>
>>> From: Gary Stanley <gary at velocity-servers.net>
>>> To: bug-followup at FreeBSD.org
>>> Cc:  Subject: Re: threads/119920: fork broken in libpthread
>>> Date: Thu, 24 Jan 2008 03:24:47 -0500
>>>
>>>  I also have this problem, see threads/118715
>>>   I was able to grab some ktrace info, but most of the time the  
>>> process  is
>>> stuck, and ktrace doesn't display any data.
>>> _______________________________________________
>>> freebsd-threads at freebsd.org mailing list
>>> http://lists.freebsd.org/mailman/listinfo/freebsd-threads
>>> To unsubscribe, send any mail to "freebsd-threads- 
>>> unsubscribe at freebsd.org"
>>
>> dan what IS the fix for this?  I assume you must have fixed it in - 
>> current/7
>
> You want cvs diff -u -r1.126 -r1.128 src/lib/libkse/thread/thr_kern.c.
> The WARNS'ify diffs are not necessary, so it should look something
> like shown below.  Probably an MFC of all of libkse (minus jasone's
> malloc changes) should be done to -7 and -6.

There appears to be a remaining issue I'm still seeing locally, with  
the above patch; I wasn't able to reproduce this on 6.2:

#0  0x0000000800648b13 in mutex_lock_common (curthread=0x0,  
m=0x8007616e8, abstime=0x0) at /usr/src/lib/libpthread/thread/ 
thr_mutex.c:503
#1  0x000000080064ac25 in _pthread_mutex_lock (m=0x8007616e8) at /usr/ 
src/lib/libpthread/thread/thr_mutex.c:868
#2  0x000000080063e9ce in _spinlock (lck=0x8009ac200) at /usr/src/lib/ 
libpthread/thread/thr_spinlock.c:97
#3  0x00000008007eafc3 in pubrealloc (ptr=0x0, size=24,  
func=0x8008802b7 " in malloc():") at /usr/src/lib/libc/stdlib/ 
malloc.c:1090
#4  0x00000008007eb1e1 in malloc (size=24) at /usr/src/lib/libc/ 
stdlib/malloc.c:1150
#5  0x000000080065ab8c in _lockuser_init (lu=0x52e068, priv=0x52e000)  
at /usr/src/lib/libpthread/sys/lock.c:99
#6  0x000000080065ac69 in _lockuser_reinit (lu=0x52e068,  
priv=0x52e000) at /usr/src/lib/libpthread/sys/lock.c:128
#7  0x000000080064d6d0 in _kse_single_thread (curthread=0x50cc00) at / 
usr/src/lib/libpthread/thread/thr_kern.c:343
#8  0x000000080063b627 in _fork () at /usr/src/lib/libpthread/thread/ 
thr_fork.c:101
#9  0x00000000004008f1 in forker ()
#10 0x000000080064516e in thread_start (curthread=0x50cc00,  
start_routine=0x4008e0 <forker>, arg=0x0) at /usr/src/lib/libpthread/ 
thread/thr_create.c:341
#11 0x00000008007b3cd9 in makectx_wrapper (ucp=0x800530860,  
func=0x800645150 <thread_start>, args=0x7fffff7fcfd0) at /usr/src/lib/ 
libc/amd64/gen/makecontext.c:100
#12 0x0000000000000000 in ?? ()
#13 0x000000000050cc00 in ?? ()
#14 0x00000000004008e0 in frame_dummy ()

via this reproduction case:

#include <sys/types.h>
#include <unistd.h>
#include <pthread.h>

void *forker (void *arg) {
          while (1) {
                  pid_t pid = fork();
                  if (pid == 0) {
                          exit(0);
                  } else if (pid > 0) {
                          int status;
                          waitpid(pid, &status, 0);
                  } else {
                          printf("Fork failed\n");
                          abort();
                  }
          }
}

int main(void) {
          int i = 0;
          for (i = 0; i < 4; i++) {
                  pthread_t thr;
                  pthread_create(&thr, NULL, forker, NULL);
                  pthread_detach(thr);
          }

          while(1)
                  sleep(1000);
}
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