Date: Sat, 4 May 2002 03:59:41 -0700 (PDT) From: Jonathan Mini <mini@FreeBSD.org> To: Perforce Change Reviews <perforce@freebsd.org> Subject: PERFORCE change 10778 for review Message-ID: <200205041059.g44Axfc02100@freefall.freebsd.org>
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http://people.freebsd.org/~peter/p4db/chv.cgi?CH=10778 Change 10778 by mini@mini_stylus on 2002/05/04 03:59:35 - Obtain PROC_LOCK when funneling through thread_single() and thread_single_end(). - For now, we know that thread_alloc() always succeeds, so don't check for failure and abort (the abort code was incorrect anyways). - Add jhb's race comment, although its not entirely accurate. Affected files ... ... //depot/projects/kse/sys/kern/kern_fork.c#65 edit Differences ... ==== //depot/projects/kse/sys/kern/kern_fork.c#65 (text+ko) ==== @@ -289,10 +289,13 @@ * be aborted in the child. * (it is possible we could restart them there as well!) */ + PROC_LOCK(p1); if (thread_single(SNGLE_WAIT)) { /* abort.. someone else is single threading before us */ + PROC_UNLOCK(p1); return (ERESTART); } + PROC_UNLOCK(p1); /* * All other activity in this process * is now suspended at the user boundary, @@ -315,9 +318,12 @@ if ((nprocs >= maxproc - 10 && uid != 0) || nprocs >= maxproc) { sx_xunlock(&allproc_lock); uma_zfree(proc_zone, newproc); + if (p1->p_flag & P_KSES) { + PROC_LOCK(p1); + thread_single_end(); + PROC_UNLOCK(p1); + } tsleep(&forksleep, PUSER, "fork", hz / 2); - if (p1->p_flag & P_KSES) - thread_single_end(); return (EAGAIN); } /* @@ -332,8 +338,11 @@ sx_xunlock(&allproc_lock); uma_zfree(proc_zone, newproc); tsleep(&forksleep, PUSER, "fork", hz / 2); - if (p1->p_flag & P_KSES) + if (p1->p_flag & P_KSES) { + PROC_LOCK(p1); thread_single_end(); + PROC_UNLOCK(p1); + } return (EAGAIN); } @@ -459,14 +468,6 @@ * then copy the section that is copied directly from the parent. */ td2 = thread_alloc(); - if (td2 == NULL) { - /* XXX need to take out of pid hash I think */ - uma_zfree(proc_zone, p2); - nprocs--; - if (p1->p_flag & P_KSES) - thread_single_end(); - return (EAGAIN); - } ke2 = &p2->p_kse; kg2 = &p2->p_ksegrp; @@ -670,6 +671,19 @@ PROC_UNLOCK(p2); sx_xunlock(&proctree_lock); + /* + * XXXKSE: In KSE, there would be a race here if one thread was + * dieing due to a signal (or calling exit1() for that matter) while + * another thread was calling fork1(). Not sure how KSE wants to work + * around that. The problem is that up until the point above, if p1 + * gets killed, it won't find p2 in its list in order for it to be + * reparented. Alternatively, we could add a new p_flag that gets set + * before we reparent all the children that we check above and just + * use init as our parent if that if that flag is set. (Either that + * or abort the fork if the flag is set since our parent died trying + * to fork us (which is evil)). + */ + KASSERT(newprocsig == NULL, ("unused newprocsig")); if (newsigacts != NULL) FREE(newsigacts, M_SUBPROC); To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe p4-projects" in the body of the message
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