threads/119920: fork broken in libpthread

[Landon Fuller]

On Jan 31, 2008, at 12:58 AM, Julian Elischer wrote:

> Landon Fuller wrote:
>
>> Thanks -- pulling in relevant change from sys/lock.c -- plus your  
>> previous patch -- solves my reproduction case:
>>    http://landonf.bikemonkey.org/static/code/freebsd/patch-libpthread63-fork
>
>
> is this the patch you used? It's huge..

Are you sure you fetched the patch-libpthread63-fork file? I cherry  
picked just the changes to _lockuser_reinit() and _kse_single_thread().

Posted patch here, inlined below:
	http://landonf.bikemonkey.org/static/code/freebsd/patch-libpthread63-fork

Cheers,
Landon

diff -ru lib/libpthread.orig/sys/lock.c lib/libpthread/sys/lock.c
--- lib/libpthread.orig/sys/lock.c	2008-01-30 16:30:07.000000000 -0800
+++ lib/libpthread/sys/lock.c	2008-01-30 16:58:59.000000000 -0800
@@ -117,14 +117,23 @@
  {
  	if (lu == NULL)
  		return (-1);
-	/*
-	 * All lockusers keep their watch request and drop their
-	 * own (lu_myreq) request.  Their own request is either
-	 * some other lockuser's watch request or is the head of
-	 * the lock.
-	 */
-	lu->lu_myreq = lu->lu_watchreq;
-	if (lu->lu_myreq == NULL)
+
+	if (lu->lu_watchreq != NULL) {
+		/*
+		 * In this case the lock is active.  All lockusers
+		 * keep their watch request and drop their own
+		 * (lu_myreq) request.  Their own request is either
+		 * some other lockuser's watch request or is the
+		 * head of the lock.
+		 */
+		lu->lu_myreq = lu->lu_watchreq;
+		lu->lu_watchreq = NULL;
+       }
+       if (lu->lu_myreq == NULL)
+		/*
+		 * Oops, something isn't quite right.  Try to
+		 * allocate one.
+		 */
  		return (_lockuser_init(lu, priv));
  	else {
  		lu->lu_myreq->lr_locked = 1;
diff -ru lib/libpthread.orig/thread/thr_kern.c lib/libpthread/thread/ 
thr_kern.c
--- lib/libpthread.orig/thread/thr_kern.c	2008-01-30  
16:30:07.000000000 -0800
+++ lib/libpthread/thread/thr_kern.c	2008-01-30 16:55:19.000000000 -0800
@@ -345,6 +345,17 @@
  		_LCK_SET_PRIVATE2(&curthread->kse->k_lockusers[i], NULL);
  	}
  	curthread->kse->k_locklevel = 0;
+
+	/*
+	 * Reinitialize the thread and signal locks so that
+	 * sigaction() will work after a fork().
+	 */
+	_lock_reinit(&curthread->lock, LCK_ADAPTIVE, _thr_lock_wait,
+	    _thr_lock_wakeup);
+	_lock_reinit(&_thread_signal_lock, LCK_ADAPTIVE, _kse_lock_wait,
+	    _kse_lock_wakeup);
+
+
  	_thr_spinlock_init();
  	if (__isthreaded) {
  		_thr_rtld_fini();
@@ -354,6 +365,20 @@
  	curthread->kse->k_kcb->kcb_kmbx.km_curthread = NULL;
  	curthread->attr.flags |= PTHREAD_SCOPE_SYSTEM;

+	/*
+	 * After a fork, it is possible that an upcall occurs in
+	 * the parent KSE that fork()'d before the child process
+	 * is fully created and before its vm space is copied.
+	 * During the upcall, the tcb is set to null or to another
+	 * thread, and this is what gets copied in the child process
+	 * when the vm space is cloned sometime after the upcall
+	 * occurs.  Note that we shouldn't have to set the kcb, but
+	 * we do it for completeness.
+	 */
+	_kcb_set(curthread->kse->k_kcb);
+	_tcb_set(curthread->kse->k_kcb, curthread->tcb);
+
+
  	/* After a fork(), there child should have no pending signals. */
  	sigemptyset(&curthread->sigpend);


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