cvs commit: src/lib/libkse/thread thr_kern.c

[Landon Fuller]

On Dec 2, 2007, at 09:31, Arno J. Klaassen wrote:

> For info, the attached patch, which partially reverts mfc of rev 1.286
> of kern_fork.c, seems to work as well (without the above patch to  
> be clear),

I just upgraded our 8-core build server from pre-november 6-STABLE to  
6.3-RELEASE, and ran into this issue, causing our fork-heavy builder  
processes to lock up regularly.

Your suggested patch (reverting the 1.286 MFC to sys/kern/ 
kern_fork.c) allows our builds to run to completion; I'll try digging  
into this further. Given how easy this is to reproduce, I'm hoping  
this is possible to fix before 6.3 is officially released?

Here's a simple reproduction case that results in instant spinning  
sub-processes:

#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 ()

#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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