mxs-dcp: BUG: init/1 still has locks held!

mxs-dcp: BUG: init/1 still has locks held!

[Fabio Estevam]

Hi,

Running linux-next 20140509 on a mx28evk I observe the following warning:

[    8.526613] Freeing unused kernel memory: 232K (c0683000 - c06bd000)
starting pid 56, tty '': '/etc/rc.d/rcS'
[    9.110314]
[    9.111864] =====================================
[    9.116603] [ BUG: init/1 still has locks held! ]
[    9.121488] 3.15.0-rc4-next-20140509-00001-g319564e #1154 Not tainted
[    9.128071] -------------------------------------
[    9.132825] 1 lock held by init/1:
[    9.136252]  #0:  (global_mutex){+.+.+.}, at: [<c0387d68>] mxs_dcp_probe+0x14
[    9.144196]
[    9.144196] stack backtrace:
[    9.148888] CPU: 0 PID: 1 Comm: init Not tainted 3.15.0-rc4-next-20140509-004
[    9.157610] [<c000da40>] (unwind_backtrace) from [<c000bda4>] (show_stack+0x)
[    9.165595] [<c000bda4>] (show_stack) from [<c00153d4>] (do_fork+0x2c8/0x3cc)
[    9.172921] [<c00153d4>] (do_fork) from [<c0015550>] (sys_vfork+0x20/0x2c)
[    9.179973] [<c0015550>] (sys_vfork) from [<c0009580>] (ret_fast_syscall+0x0)
Mounting /proc and /sys

Should we really use a global mutex here? What is a proper fix for this?

Regards,

Fabio Estevam

Re: mxs-dcp: BUG: init/1 still has locks held!

[Alexander Shiyan]

Sun, 11 May 2014 16:57:57 -0300 ?? Fabio Estevam <festevam@gmail.com>:
> Hi,
> 
> Running linux-next 20140509 on a mx28evk I observe the following warning:
> 
> [    8.526613] Freeing unused kernel memory: 232K (c0683000 - c06bd000)
> starting pid 56, tty '': '/etc/rc.d/rcS'
> [    9.110314]
> [    9.111864] =====================================
> [    9.116603] [ BUG: init/1 still has locks held! ]
> [    9.121488] 3.15.0-rc4-next-20140509-00001-g319564e #1154 Not tainted
> [    9.128071] -------------------------------------
> [    9.132825] 1 lock held by init/1:
> [    9.136252]  #0:  (global_mutex){+.+.+.}, at: [<c0387d68>] mxs_dcp_probe+0x14
> [    9.144196]
> [    9.144196] stack backtrace:
> [    9.148888] CPU: 0 PID: 1 Comm: init Not tainted 3.15.0-rc4-next-20140509-004
> [    9.157610] [<c000da40>] (unwind_backtrace) from [<c000bda4>] (show_stack+0x)
> [    9.165595] [<c000bda4>] (show_stack) from [<c00153d4>] (do_fork+0x2c8/0x3cc)
> [    9.172921] [<c00153d4>] (do_fork) from [<c0015550>] (sys_vfork+0x20/0x2c)
> [    9.179973] [<c0015550>] (sys_vfork) from [<c0009580>] (ret_fast_syscall+0x0)
> Mounting /proc and /sys
> 
> Should we really use a global mutex here? What is a proper fix for this?

On my opinion mutex_lock/unlock should not be used in probe.
Try to remove this entirely.

---

mxs-dcp: BUG: init/1 still has locks held!

[Fabio Estevam]

On Sun, May 11, 2014 at 5:08 PM, Alexander Shiyan <shc_work@mail.ru> wrote:
> Sun, 11 May 2014 16:57:57 -0300 ?? Fabio Estevam <festevam@gmail.com>:
>> Hi,
>>
>> Running linux-next 20140509 on a mx28evk I observe the following warning:
>>
>> [    8.526613] Freeing unused kernel memory: 232K (c0683000 - c06bd000)
>> starting pid 56, tty '': '/etc/rc.d/rcS'
>> [    9.110314]
>> [    9.111864] =====================================
>> [    9.116603] [ BUG: init/1 still has locks held! ]
>> [    9.121488] 3.15.0-rc4-next-20140509-00001-g319564e #1154 Not tainted
>> [    9.128071] -------------------------------------
>> [    9.132825] 1 lock held by init/1:
>> [    9.136252]  #0:  (global_mutex){+.+.+.}, at: [<c0387d68>] mxs_dcp_probe+0x14
>> [    9.144196]
>> [    9.144196] stack backtrace:
>> [    9.148888] CPU: 0 PID: 1 Comm: init Not tainted 3.15.0-rc4-next-20140509-004
>> [    9.157610] [<c000da40>] (unwind_backtrace) from [<c000bda4>] (show_stack+0x)
>> [    9.165595] [<c000bda4>] (show_stack) from [<c00153d4>] (do_fork+0x2c8/0x3cc)
>> [    9.172921] [<c00153d4>] (do_fork) from [<c0015550>] (sys_vfork+0x20/0x2c)
>> [    9.179973] [<c0015550>] (sys_vfork) from [<c0009580>] (ret_fast_syscall+0x0)
>> Mounting /proc and /sys
>>
>> Should we really use a global mutex here? What is a proper fix for this?
>
> On my opinion mutex_lock/unlock should not be used in probe.
> Try to remove this entirely.

I think the same. Will submit a patch doing as suggested.

Regards,

Fabio Estevam

Re: mxs-dcp: BUG: init/1 still has locks held!

[Alexander Shiyan]

Sun, 11 May 2014 17:09:27 -0300 ?? Fabio Estevam <festevam@gmail.com>:
> On Sun, May 11, 2014 at 5:08 PM, Alexander Shiyan <shc_work@mail.ru> wrote:
> > Sun, 11 May 2014 16:57:57 -0300 ?? Fabio Estevam <festevam@gmail.com>:
> >> Hi,
> >>
> >> Running linux-next 20140509 on a mx28evk I observe the following warning:
> >>
> >> [    8.526613] Freeing unused kernel memory: 232K (c0683000 - c06bd000)
> >> starting pid 56, tty '': '/etc/rc.d/rcS'
> >> [    9.110314]
> >> [    9.111864] =====================================
> >> [    9.116603] [ BUG: init/1 still has locks held! ]
> >> [    9.121488] 3.15.0-rc4-next-20140509-00001-g319564e #1154 Not tainted
> >> [    9.128071] -------------------------------------
> >> [    9.132825] 1 lock held by init/1:
> >> [    9.136252]  #0:  (global_mutex){+.+.+.}, at: [<c0387d68>] mxs_dcp_probe+0x14
> >> [    9.144196]
> >> [    9.144196] stack backtrace:
> >> [    9.148888] CPU: 0 PID: 1 Comm: init Not tainted 3.15.0-rc4-next-20140509-004
> >> [    9.157610] [<c000da40>] (unwind_backtrace) from [<c000bda4>] (show_stack+0x)
> >> [    9.165595] [<c000bda4>] (show_stack) from [<c00153d4>] (do_fork+0x2c8/0x3cc)
> >> [    9.172921] [<c00153d4>] (do_fork) from [<c0015550>] (sys_vfork+0x20/0x2c)
> >> [    9.179973] [<c0015550>] (sys_vfork) from [<c0009580>] (ret_fast_syscall+0x0)
> >> Mounting /proc and /sys
> >>
> >> Should we really use a global mutex here? What is a proper fix for this?
> >
> > On my opinion mutex_lock/unlock should not be used in probe.
> > Try to remove this entirely.
> 
> I think the same. Will submit a patch doing as suggested.

AFAIK, probe/remove are serialized and running only on one CPU/thread,
so any mutexes/spinlocks really not needed.

2ML: Please, FIXME if I am think incorrect.

---