On Thu, 12 Jul 2012, Mike Galbraith wrote:
> On Thu, 2012-07-12 at 10:44 +0200, Mike Galbraith wrote:
> > On Thu, 2012-07-12 at 07:47 +0200, Mike Galbraith wrote:
> > > Greetings,
> > >
> > > I'm chasing btrfs critters in an enterprise 3.0-rt kernel, and just
> > > checked to see if they're alive in virgin latest/greatest rt kernel.
> > >
> > > Both are indeed alive and well, ie I didn't break it, nor did the
> > > zillion patches in enterprise base kernel, so others may have an
> > > opportunity to meet these critters up close and personal as well.
> >
> > 3.2-rt both explodes and deadlocks as well. 3.0-rt (virgin I mean) does
> > neither, so with enough re-integrate investment, it might be bisectable.
>
> Nope, virgin 3.0-rt just didn't feel like it at the time. Booted it
> again to run hefty test over lunch, it didn't survive 1 xfstests 006,
> much less hundreds.
>
> crash> bt
> PID: 7604 TASK: ffff880174238b20 CPU: 0 COMMAND: "btrfs-worker-0"
> #0 [ffff88017455d9c8] machine_kexec at ffffffff81025794
> #1 [ffff88017455da28] crash_kexec at ffffffff8109781d
> #2 [ffff88017455daf8] panic at ffffffff814a0661
> #3 [ffff88017455db78] __try_to_take_rt_mutex at ffffffff81086d2f
> #4 [ffff88017455dbc8] rt_spin_lock_slowlock at ffffffff814a2670
> #5 [ffff88017455dca8] rt_spin_lock at ffffffff814a2db9
> #6 [ffff88017455dcb8] schedule_bio at ffffffff81243133
> #7 [ffff88017455dcf8] btrfs_map_bio at ffffffff812477be
> #8 [ffff88017455dd68] __btree_submit_bio_done at ffffffff812152f6
> #9 [ffff88017455dd78] run_one_async_done at ffffffff812148fa
> #10 [ffff88017455dd98] run_ordered_completions at ffffffff812493e8
> #11 [ffff88017455ddd8] worker_loop at ffffffff81249dc9
> #12 [ffff88017455de88] kthread at ffffffff81070266
> #13 [ffff88017455df48] kernel_thread_helper at ffffffff814a9be4
> crash> struct rt_mutex 0xffff880174530108
> struct rt_mutex {
> wait_lock = {
> raw_lock = {
> slock = 7966
> }
> },
> wait_list = {
> node_list = {
> next = 0xffff880175ecc970,
> prev = 0xffff880175ecc970
> },
> rawlock = 0xffff880175ecc968,
Pointer into lala land again.
rawlock points to ...968 and the node_list to ...970.
struct rt_mutex {
raw_spinlock_t wait_lock;
struct plist_head wait_list;
The raw_lock pointer of the plist_head is initialized in
__rt_mutex_init() so it points to wait_lock.
Can you check the offset of wait_list vs. the rt_mutex itself?
I wouldn't be surprised if it's exactly 8 bytes. And then this thing
looks like a copied lock with stale pointers to hell. Eew.
Thanks,
tglx
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