Hi Robert, I don't think your patch is correct, the total linked list can be broken while the lock is released, thus just passing the link may not be enough I have submitted a PR[1] for this a month ago but nobody took care of it yet Regards, Antoine Pelisse
[1] http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/84684 On 9/29/05, Robert Watson <[EMAIL PROTECTED]> wrote: > > On Thu, 29 Sep 2005, Rob Watt wrote: > > > On Thu, 29 Sep 2005, Robert Watson wrote: > > > >> Could you dump the contents of *td and *td->td_proc for me? I'm quite > >> interested to know what the value in td->td_proc->p_state is, among > other > >> things. If I could also have you generate a dump of the KSE group > >> structures in td->td_proc->p_ksegrps and the threads in > >> td->td_proc->p_threads. > > > > I've attached a file with many of the values you have asked for. We > > looked at some of the threads referenced by td->td_proc->p_threads, but > > we weren't sure we were walking the list correctly. Do you have any tips > > > for walking those thread lists? > > > >> Could you tell me if the program named by p->p_comm is linked against a > >> threading library? If it's a custom app, you may already know, and if > >> not, you can run ldd on the application to see what it is linked > >> against. > > > > The programs named by p->p_comm is linked against the pthreads library. > > This seems to be enough information to at least track this down a bit: > td_ksegrp is NULL, rather than a corrupt value, which suggests that the > thread is incompletely initialized. Other hints that this are the case > are that td_critnest is 1 (as is set when it is allocated), and the state > is TDS_INACTIVE. Some other fields are set though, such as td_oncpu, > which is normally initialized to NOCPU. > > > (kgdb) p *td > > $1 = {td_proc = 0xffffff004aa9f000, td_ksegrp = 0x0, td_plist = > > {tqe_next = 0xff ffff00b4798000, > > tqe_prev = 0xffffff00a97ae010}, td_kglist = {tqe_next = > > 0xffffff00b4798000, > > tqe_prev = 0xffffff00a97ae020}, td_slpq = {tqe_next = 0x0, tqe_prev > > = 0xffff ff001fac7c10}, td_lockq = { > > tqe_next = 0xffffff00a97ae000, tqe_prev = 0xffffffffb6797a70}, > > td_runq = {tq e_next = 0x0, > > tqe_prev = 0xffffffff80608180}, td_selq = {tqh_first = 0x0, tqh_last > > = 0xfff fff00633112c0}, > > td_sleepqueue = 0xffffff00382b0400, td_turnstile = 0xffffff00c1712900, > > td_umtx q = 0xffffff00d1207080, > > td_tid = 100253, td_flags = 16777216, td_inhibitors = 0, td_pflags = > > 128, td_d upfd = 0, td_wchan = 0x0, > > td_wmesg = 0x0, td_lastcpu = 2 '\002', td_oncpu = 2 '\002', > > td_owepreempt = 0 '\0', td_locks = 0, > > td_blocked = 0x0, td_ithd = 0x0, td_lockname = 0x0, td_contested = > > {lh_first = > > 0x0}, td_sleeplocks = 0x0, > > td_intr_nesting_level = 0, td_pinned = 0, td_mailbox = 0x0, td_ucred = > > 0xfffff f00ad18f200, > > td_standin = 0x0, td_upcall = 0x0, td_sticks = 0, td_uuticks = 0, > > td_usticks = > > 0, td_intrval = 0, > > td_oldsigmask = {__bits = {0, 0, 0, 0}}, td_sigmask = {__bits = > > {4294967295, 4 294967295, 4294967295, > > 4294967295}}, td_siglist = {__bits = {0, 0, 0, 0}}, td_generation > > = 14, td _sigstk = {ss_sp = 0x0, > > ss_size = 0, ss_flags = 0}, td_kflags = 0, td_xsig = 0, > > td_profil_addr = 0, td_profil_ticks = 0, > > td_base_pri = 182 '\uffff', td_priority = 182 '\uffff', td_pcb = > > 0xffffffffb68 dcd10, td_state = TDS_INACTIVE, > > td_retval = {1, 29309280}, td_slpcallout = {c_links = {sle = {sle_next > > = 0x0}, > > tqe = {tqe_next = 0x0, > > tqe_prev = 0xffffff001fac7d80}}, c_time = 55907602, c_arg = > > 0xffffff0063 311260, > > c_func = 0xffffffff802e32a0 <sleepq_timeout>, c_mtx = 0x0, c_flags = > > 16}, td _frame = 0xffffffffb68dcc40, > > td_kstack_obj = 0xffffff0087f93d20, td_kstack = 18446744072477315072, > > td_kstac k_pages = 4, > > td_altkstack_obj = 0x0, td_altkstack = 0, td_altkstack_pages = 0, > > td_critnest = 1, td_md = { > > md_spinlock_count = 1, md_saved_flags = 582}, td_sched = > > 0xffffff0063311488} > > I'm not familiar with the internals of the thread and KSE life cycle here, > > so I think we'll need to look to those more familiar with this to > understand what of two things may be going on: > > (1) Is the fact that td_ksegrp != NULL an invariant for a connected > thread, and that kern_proc is relying on that but the thread code is > failing to implement it safely? > > (2) Is td_ksegrp sometimes left legitimately as NULL as part of the thread > life cycle, and that kern_proc incorrectly assumes that it is never > NULL when hooked up to a thread. > > This suggests a possible work-around of simply testing td_ksegrp for NULL > in kern_proc in order to avoid this, while attempting to resolve whether > an invariant is violated (or incorrectly assumed), which might require > some serious thinking and a solution that is non-trivial. Something like > the following might work in the mean time: > > Index: kern_proc.c > =================================================================== > RCS file: /home/ncvs/src/sys/kern/kern_proc.c,v > retrieving revision 1.231 > diff -u -r1.231 kern_proc.c > --- kern_proc.c 27 Sep 2005 18:03:15 -0000 1.231 > +++ kern_proc.c 29 Sep 2005 20:50:33 -0000 > @@ -882,6 +882,8 @@ > } else { > _PHOLD(p); > FOREACH_THREAD_IN_PROC(p, td) { > + if (td->td_ksegrp == NULL) > + continue; > fill_kinfo_thread(td, &kinfo_proc); > PROC_UNLOCK(p); > error = SYSCTL_OUT(req, (caddr_t)&kinfo_proc, > > I'm going to forward off your e-mail to the threads@ list and see if > anyone there wants to talk some more about this. If you don't mind > testing the above patch to see if this is a workable work-around, we may > want to think about getting it committed in the mean time. > > Thanks, > > Robert N M Watson > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "[EMAIL PROTECTED]" > _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[EMAIL PROTECTED]"
