Re: [GIT PULL rcu/urgent] Fix two more 4.3 regressions

From: Paul E. McKenney
Date: Sun Sep 27 2015 - 12:44:09 EST

On Sun, Sep 27, 2015 at 06:25:37PM +0200, Sedat Dilek wrote:
> On Sun, Sep 27, 2015 at 6:16 PM, Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote:
> > On Sun, Sep 27, 2015 at 6:02 PM, Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote:
> >> On Sun, Sep 27, 2015 at 5:58 PM, Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote:
> >>> On Sun, Sep 27, 2015 at 5:55 PM, Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote:
> >>>> On Sun, Sep 27, 2015 at 5:49 PM, Paul E. McKenney
> >>>> <paulmck@xxxxxxxxxxxxxxxxxx> wrote:
> >>>>> On Sun, Sep 27, 2015 at 09:37:05AM +0200, Sedat Dilek wrote:
> >>>>>> On Sun, Sep 27, 2015 at 9:32 AM, Paul E. McKenney
> >>>>>> <paulmck@xxxxxxxxxxxxxxxxxx> wrote:
> >>>>>> > On Sun, Sep 27, 2015 at 08:28:39AM +0200, Sedat Dilek wrote:
> >>>>>> >> Hi,
> >>>>>> >>
> >>>>>> >> as I have observed here some lockdep issues (one could be solved in
> >>>>>> >> netdev) I wanted to try this patchset.
> >>>>>> >>
> >>>>>> >> Unfortunately, you cannot pull from...
> >>>>>> >>
> >>>>>> >> "These changes are available in the git repository at:
> >>>>>> >>
> >>>>>> >> git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git for-mingo
> >>>>>> >>
> >>>>>> >> for you to fetch changes up to 19a5ecde086a6a5287978b12ae948fa691b197b7:
> >>>>>> >>
> >>>>>> >> rcu: Suppress lockdep false positive for rcp->exp_funnel_mutex
> >>>>>> >> (2015-09-20 21:01:22 -0700)
> >>>>>> >>
> >>>>>> >> ----------------------------------------------------------------
> >>>>>> >> Oleg Nesterov (1):
> >>>>>> >> rcu: Change _wait_rcu_gp() to work around GCC bug 67055
> >>>>>> >>
> >>>>>> >> Paul E. McKenney (1):
> >>>>>> >> rcu: Suppress lockdep false positive for rcp->exp_funnel_mutex
> >>>>>> >>
> >>>>>> >> include/linux/rcupdate.h | 11 +++++------
> >>>>>> >> kernel/rcu/tree.c | 5 +++++
> >>>>>> >> 2 files changed, 10 insertions(+), 6 deletions(-)"
> >>>>>> >>
> >>>>>> >> So, I have stolen them from linux-next.git.
> >>>>>> >>
> >>>>>> >> Please look at this, Thanks.
> >>>>>> >
> >>>>>> > Does it work better now? (Forgot to actually push the new name...)
> >>>>>>
> >>>>>> Hi Paul,
> >>>>>>
> >>>>>> now for-mingo Git branch has this two fixes.
> >>>>>
> >>>>> Whew!!! Apologies for the hassle!
> >>>>>
> >>>>>> I just booted into my new kernel with the "stolen" rcu.fixes from -next.
> >>>>>>
> >>>>>> For the lockdep problems I will do a CONFIG_DEBUG_LOCKDEP=y to see if
> >>>>>> I get some more infos on the workqueue trouble.
> >>>>>>
> >>>>>> [ 23.874836] BUG: sleeping function called from invalid context at
> >>>>>> kernel/workqueue.c:2678
> >>>>>> [ 23.874902] in_atomic(): 0, irqs_disabled(): 1, pid: 1411, name: acpid
> >>>>>
> >>>>> Did you get a stack trace? There are quite a few potential callers of
> >>>>> start_flush_work() via flush_work().
> >>>>>
> >>>>
> >>>> Hi Paul :-),
> >>>>
> >>>> Here is the stack trace.
> >>>>
> >>>> [ 23.045871] BUG: sleeping function called from invalid context at
> >>>> kernel/workqueue.c:2678
> >>>> [ 23.045982] in_atomic(): 0, irqs_disabled(): 1, pid: 1399, name: acpid
> >>>> [ 23.046064] 3 locks held by acpid/1399:
> >>>> [ 23.046066] #0: (&evdev->mutex){+.+...}, at: [<ffffffff8174ac7c>]
> >>>> evdev_release+0xbc/0xf0
> >>>> [ 23.046081] #1: (&dev->mutex#2){+.+...}, at: [<ffffffff81742397>]
> >>>> input_close_device+0x27/0x70
> >>>> [ 23.046093] #2: (hid_open_mut){+.+...}, at: [<ffffffffa0056388>]
> >>>> usbhid_close+0x28/0xb0 [usbhid]
> >>>> [ 23.046106] irq event stamp: 3306
> >>>> [ 23.046109] hardirqs last enabled at (3305): [<ffffffff8192ae32>]
> >>>> _raw_spin_unlock_irq+0x32/0x60
> >>>> [ 23.046115] hardirqs last disabled at (3306): [<ffffffff81121017>]
> >>>> del_timer_sync+0x37/0x110
> >>>> [ 23.046122] softirqs last enabled at (2704): [<ffffffff818b12c9>]
> >>>> local_bh_enable+0x9/0x20
> >>>> [ 23.046128] softirqs last disabled at (2702): [<ffffffff818b12a9>]
> >>>> local_bh_disable+0x9/0x20
> >>>> [ 23.046136] CPU: 2 PID: 1399 Comm: acpid Not tainted
> >>>> 4.3.0-rc3-3-llvmlinux-amd64 #1
> >>>> [ 23.046139] Hardware name: SAMSUNG ELECTRONICS CO., LTD.
> >>>> 530U3BI/530U4BI/530U4BH/530U3BI/530U4BI/530U4BH, BIOS 13XK 03/28/2013
> >>>> [ 23.046143] ffff8800d36ee948 0000000000000092 0000000000000000
> >>>> ffff8800bbacfae8
> >>>> [ 23.046151] ffffffff8149adad ffff8800bbacfb18 ffffffff810cd1ea
> >>>> ffffffff81c56f0a
> >>>> [ 23.046158] ffff8800c22dc400 0000000000000000 0000000000000a76
> >>>> ffff8800bbacfb58
> >>>> [ 23.046165] Call Trace:
> >>>> [ 23.046172] [<ffffffff8149adad>] dump_stack+0x7d/0xa0
> >>>> [ 23.046177] [<ffffffff810cd1ea>] ___might_sleep+0x28a/0x2a0
> >>>> [ 23.046182] [<ffffffff810cceef>] __might_sleep+0x4f/0xc0
> >>>> [ 23.046187] [<ffffffff810afbff>] start_flush_work+0x2f/0x290
> >>>> [ 23.046192] [<ffffffff810afbac>] flush_work+0x5c/0x80
> >>>> [ 23.046195] [<ffffffff810afb6a>] ? flush_work+0x1a/0x80
> >>>> [ 23.046202] [<ffffffff810eed0d>] ? trace_hardirqs_off+0xd/0x10
> >>>> [ 23.046206] [<ffffffff810aecc8>] ? try_to_grab_pending+0x48/0x360
> >>>> [ 23.046211] [<ffffffff8192ac53>] ? _raw_spin_lock_irqsave+0x73/0x80
> >>>> [ 23.046216] [<ffffffff810afff9>] __cancel_work_timer+0x179/0x260
> >>>> [ 23.046221] [<ffffffff8192add2>] ? _raw_spin_unlock_irqrestore+0x52/0x80
> >>>> [ 23.046226] [<ffffffff81120fcd>] ? try_to_del_timer_sync+0xad/0xc0
> >>>> [ 23.046230] [<ffffffff810afe78>] cancel_work_sync+0x18/0x20
> >>>> [ 23.046237] [<ffffffffa00563d5>] usbhid_close+0x75/0xb0 [usbhid]
> >>>> [ 23.046245] [<ffffffffa00394d1>] hidinput_close+0x31/0x40 [hid]
> >>>> [ 23.046251] [<ffffffffa00394a0>] ? hidinput_open+0x40/0x40 [hid]
> >>>> [ 23.046256] [<ffffffff817423b8>] input_close_device+0x48/0x70
> >>>> [ 23.046261] [<ffffffff8174ac96>] evdev_release+0xd6/0xf0
> >>>> [ 23.046267] [<ffffffff812728c7>] __fput+0x107/0x240
> >>>> [ 23.046271] [<ffffffff81272756>] ____fput+0x16/0x20
> >>>> [ 23.046276] [<ffffffff810b945c>] task_work_run+0x6c/0xe0
> >>>> [ 23.046282] [<ffffffff81003aa7>] prepare_exit_to_usermode+0x117/0x120
> >>>> [ 23.046287] [<ffffffff81003ce1>] syscall_return_slowpath+0x231/0x2a0
> >>>> [ 23.046292] [<ffffffff8126efa5>] ? filp_close+0x65/0x90
> >>>> [ 23.046298] [<ffffffff810ef1c9>] ? trace_hardirqs_on_caller+0x19/0x290
> >>>> [ 23.046303] [<ffffffff81003017>] ? trace_hardirqs_on_thunk+0x17/0x19
> >>>> [ 23.046308] [<ffffffff8192bb62>] int_ret_from_sys_call+0x25/0x9f
> >>>>
> >>>> Can you give help on how to "debug" this?
> >>>>
> >>>> I switched from full-dynticks to simple cpu-accounting which did not help.
> >>>> But this was only a suspicion as Jiri pointed to the possibility
> >>>> del_timer_sync() could have get some mis-optimization.
> >>>>
> >>>> So, more empty head here.
> >>>>
> >>>
> >>> Forgot to attach dmesg-log and my kernel-config.
> >>> Sorry about that.
> >>>
> >>
> >> Time for a pause!
> >>
> >> Forgot to attach disassembled kernel/workqueue.o.
> >>
> >
> > When looking at start_flush_work() in kernel/workqueue.c...
> > ...I remembered the comments of Lai Jiangshan concerning the
> > might_sleep() check there.
> >
> > I tried to move the might_sleep() line to __cancel_work_timer() as
> > requested, but that did not help or narrowed down whatever.
> >
> > Please see [1] for more details.
> >
> > - Sedat -
> >
> > [1] http://marc.info/?l=linux-kernel&m=144184707824750&w=2
>
> Sorry, before you dig to deeply inside this.
>
> Jiri made a good analysis on the hid side looking at my stack trace... see [2].

Good. Might be that clang/LLVM needs some help here. ;-)

Thanx, Paul

> - Sedat -
>
> [2] http://marc.info/?l=linux-kernel&m=144308152407025&w=2
>

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