Messages in this thread | | | Date | Sun, 2 Aug 2009 03:56:02 +0530 | From | Balbir Singh <> | Subject | Re: memory-controller patch fails to boot in qemu [mmotm] |
| |
* Hugh Dickins <hugh.dickins@tiscali.co.uk> [2009-08-01 23:09:09]:
> On Sun, 2 Aug 2009, Balbir Singh wrote: > > * Jiri Slaby <jirislaby@gmail.com> [2009-08-01 16:07:38]: > > > > > > in mmotm-2009-07-30-05-01, the patch named > > > memory-controller-soft-limit-organize-cgroups-v9.patch > > > causes qemu fail to boot with tons of: > > > BUG: scheduling while atomic: async/2/480/0x10000002 > > > Modules linked in: > > > Pid: 480, comm: async/2 Tainted: G AW 2.6.31-rc4-mm1-bh #13 > > > Call Trace: > > > [<ffffffff81036b6c>] __schedule_bug+0x5c/0x70 > > > [<ffffffff8140491b>] thread_return+0x5c1/0x786 > > > [<ffffffff8103dd30>] __cond_resched+0x20/0x50 > > > [<ffffffff81404b9d>] _cond_resched+0x2d/0x40 > > > [<ffffffff81096694>] truncate_inode_pages_range+0x224/0x450 > > > [<ffffffff8106dfa1>] ? smp_call_function_many+0x1e1/0x210 > > > [<ffffffff810e50d0>] ? invalidate_bh_lru+0x0/0x90 > > > [<ffffffff810e514b>] ? invalidate_bh_lru+0x7b/0x90 > > > [<ffffffff810e50d0>] ? invalidate_bh_lru+0x0/0x90 > > > [<ffffffff810968d0>] truncate_inode_pages+0x10/0x20 > > > [<ffffffff810ea875>] kill_bdev+0x35/0x40 > > > [<ffffffff810eba18>] __blkdev_put+0xa8/0x190 > > > [<ffffffff810ebb0b>] blkdev_put+0xb/0x10 > > > [<ffffffff81116f62>] register_disk+0x172/0x180 > > > [<ffffffff8115bca5>] add_disk+0x85/0x150 > > > [<ffffffff812398cf>] sd_probe_async+0x12f/0x200 > > > [<ffffffff810616ca>] async_thread+0x10a/0x270 > > > [<ffffffff8103f7a0>] ? default_wake_function+0x0/0x10 > > > [<ffffffff810615c0>] ? async_thread+0x0/0x270 > > > [<ffffffff8105ac66>] kthread+0x96/0xa0 > > > [<ffffffff8100ceaa>] child_rip+0xa/0x20 > > > [<ffffffff8105abd0>] ? kthread+0x0/0xa0 > > > [<ffffffff8100cea0>] ? child_rip+0x0/0x20 > > > > > > Looks like an omitted unlock. I don't see anything suspicious in the > > > patch though. > > > > > > Thanks for the report, did you bisect the mmotm series to identify the > > root cause? What does your .config look like? I tried kvm with the > > patches (mmotm 30th July) and qemu-kvm (30th-july) with a Fedora 11 > > guest image and the system booted just fine for me. > > > > Could you share your command line as well? > > I've just finished chasing something similar (without qemu), > and was about to post this: > > [PATCH mmotm] memory controller: soft limit organize cgroups v9 fix > > CONFIG_CGROUP_MEM_RES_CTLR=y CONFIG_PREEMPT=y mmotm fails to boot: > Kernel panic - not syncing: No init found; after lots of scheduling > while atomics, starting from when async_thread does sd_probe_async. > > mem_cgroup_soft_limit_check() was doing an unbalanced get_cpu(): > don't get_cpu if we won't need it, and put_cpu if we did get_cpu. > > Hmm, this a weird function, passed an argument just to tell it to do > nothing. Perhaps a placeholder for something more sensible to come?
The argument is passed a result of a function, It no-ops quite frequently for the root cgroup.
> > Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk> > --- > Fix to memory-controller-soft-limit-organize-cgroups-v9.patch > > mm/memcontrol.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > --- mmotm/mm/memcontrol.c 2009-08-01 05:48:08.000000000 +0100 > +++ linux/mm/memcontrol.c 2009-08-01 21:45:37.000000000 +0100 > @@ -375,19 +375,21 @@ static bool mem_cgroup_soft_limit_check( > bool over_soft_limit) > { > bool ret = false; > - int cpu = get_cpu(); > + int cpu; > s64 val; > struct mem_cgroup_stat_cpu *cpustat; > > if (!over_soft_limit) > return ret; > > + cpu = get_cpu(); > cpustat = &mem->stat.cpustat[cpu]; > val = __mem_cgroup_stat_read_local(cpustat, MEM_CGROUP_STAT_EVENTS); > if (unlikely(val > SOFTLIMIT_EVENTS_THRESH)) { > __mem_cgroup_stat_reset_safe(cpustat, MEM_CGROUP_STAT_EVENTS); > ret = true; > } > + put_cpu(); > return ret; > } >
Thanks, my bad, I should have spotted the missing put_cpu(). I'll test this with CONFIG_PREEMPT, CONFIG_PREEMPT_DEBUG and report back. The patch obviously looks correct, but I'll test it as well.
-- Balbir
| |