Messages in this thread | | | Date | Sun, 14 Nov 2010 18:49:21 +0100 | From | Markus Trippelsdorf <> | Subject | Re: [RFC/RFT PATCH v3] sched: automated per tty task groups |
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On 2010.11.14 at 10:19 -0700, Mike Galbraith wrote: > On Sat, 2010-11-13 at 04:42 -0700, Mike Galbraith wrote: > > On Fri, 2010-11-12 at 19:12 +0100, Oleg Nesterov wrote: > > > On 11/11, Mike Galbraith wrote: > > > > > > > > On Thu, 2010-11-11 at 21:27 +0100, Oleg Nesterov wrote: > > > > > > > > > But the real problem is that copy_process() can fail after that, > > > > > and in this case we have the unbalanced kref_get(). > > > > > > > > Memory leak, will fix. > > > > > > > > > > +++ linux-2.6.36.git/kernel/exit.c > > > > > > @@ -174,6 +174,7 @@ repeat: > > > > > > write_lock_irq(&tasklist_lock); > > > > > > tracehook_finish_release_task(p); > > > > > > __exit_signal(p); > > > > > > + sched_autogroup_exit(p); > > > > > > > > > > This doesn't look right. Note that "p" can run/sleep after that > > > > > (or in parallel), set_task_rq() can use the freed ->autogroup. > > > > > > > > So avoiding refcounting rcu released task_group backfired. Crud. > > > > > > Just in case, the lock order may be wrong. sched_autogroup_exit() > > > takes task_group_lock under write_lock(tasklist), while > > > sched_autogroup_handler() takes them in reverse order. > > > > Bug self destructs when global classifier goes away. > > I didn't nuke the handler, but did hide it under a debug option since it > is useful for testing. If the user enables it, and turns autogroup off, > imho off should means off NOW, so I stuck with it as is. I coded up a > lazy (tick time check) move to handle pinned tasks not otherwise being > moved, but that was too much for even my (lack of) taste to handle. > > The locking should be fine as it was now, since autogroup_exit() isn't > under the tasklist lock any more. (surprising i didn't hit any problems > with this or use after free in rt kernel given how hard i beat on it) > > Pondering adding some debug bits to identify autogroup tasks, maybe > in /proc/N/cgroup or such. > > > > I am not sure, but perhaps this can be simpler? > > > wake_up_new_task() does autogroup_fork(), and do_exit() does > > > sched_autogroup_exit() before the last schedule. Possible? > > > > That's what I was going to do. That said, I couldn't have had the > > problem if I'd tied final put directly to life of container, and am > > thinking I should do that instead when I go back to p->signal. > > I ended up tying it directly to p->signal's life, and beat on it with > CONFIG_PREEMPT. I wanted to give it a thrashing in PREEMPT_RT, but > when I snagged your signal patches, I apparently didn't snag quite > enough, as the rt kernel with those patches is early boot doorstop. > > > > Very basic question. Currently sched_autogroup_create_attach() > > > has the only caller, __proc_set_tty(). It is a bit strange that > > > signal->tty change is process-wide, but sched_autogroup_create_attach() > > > move the single thread, the caller. What about other threads in > > > this thread group? The same for proc_clear_tty(). > > > > Yeah, I really should (will) move all on the spot... > > Did that, and the rest. This patch will apply to tip or .git.
Unfortunately it won't. There's a missing "+" at line 507:
markus@arch linux % patch -p1 --dry-run < /home/markus/tty_autogroup2.patch patching file include/linux/sched.h Hunk #3 succeeded at 1935 (offset -1 lines). patching file kernel/sched.c Hunk #2 succeeded at 607 (offset 1 line). Hunk #3 succeeded at 2011 with fuzz 2 (offset 1 line). Hunk #4 succeeded at 7959 (offset -25 lines). Hunk #5 succeeded at 8489 (offset -25 lines). Hunk #6 succeeded at 8514 (offset -25 lines). patching file kernel/fork.c patching file drivers/tty/tty_io.c patching file kernel/sched_autogroup.h patching file kernel/sched_autogroup.c patch: **** malformed patch at line 507: Index: linux-2.6/kernel/sysctl.c -- Markus
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