[v3,0/3] Add lockdep_assert_not_held()

Message

Shuah Khan Feb. 27, 2021, 12:06 a.m. UTC

Some kernel functions must not be called holding a specific lock. Doing
so could lead to locking problems. Currently these routines call
lock_is_held() to check for lock hold followed by WARN_ON.

Adding a common lockdep interface will help reduce the duplication of this
logic in the rest of the kernel.

Add lockdep_assert_not_held() to be used in these functions to detect
incorrect calls while holding a lock.

lockdep_assert_not_held() provides the opposite functionality of
lockdep_assert_held() which is used to assert calls that require
holding a specific lock.

The need for lockdep_assert_not_held() came up in a discussion on
ath10k patch. ath10k_drain_tx() and i915_vma_pin_ww() are examples
of functions that can use lockdep_assert_not_held().

Link: https://lore.kernel.org/lkml/[e-mail]/
Link: https://lore.kernel.org/linux-wireless/[e-mail]/

This patch series adds lockdep_assert_not_held() and uses it in the
second patch in ath10k_drain_tx() function.

Changes since v2:
-- Fixed coding style issues
-- Patch 2 uses new lock states in __lock_is_held() and
   lock_is_held_type

Patch 1 incorporates suggestions from Peter Zijlstra on v1 series
to avoid misfires when lockdep_off() is employed.

Patch 2 Johannes Berg's suggestions as it make it easier to read and
maintain the lock states. These are defines and a enum to avoid changes
to lock_is_held_type() and lockdep_is_held() return types.

Patch 2 is a separate patch because it adds defines to lockdep.h and
kernel/locking/lockdep.c now includes lockdep.h - decided make this
a separate patch just in case issues related to header dependencies
pop up. I can combine Patches 1&2 if that is preferred.

Patch 3 uses the new interface in ath10k_drain_tx() function. Added
Kalle Valo's Ack from v1 for this change.

Tested on the mainline from yesterday.

Shuah Khan (3):
  lockdep: add lockdep_assert_not_held()
  lockdep: add lockdep lock state defines
  ath10k: detect conf_mutex held ath10k_drain_tx() calls

 drivers/net/wireless/ath/ath10k/mac.c |  2 ++
 include/linux/lockdep.h               | 18 +++++++++++++++---
 kernel/locking/lockdep.c              | 15 ++++++++++-----
 3 files changed, 27 insertions(+), 8 deletions(-)

Comments

Peter Zijlstra March 1, 2021, 8:38 a.m. UTC | #1

On Fri, Feb 26, 2021 at 05:06:57PM -0700, Shuah Khan wrote:
> Shuah Khan (3):
>   lockdep: add lockdep_assert_not_held()
>   lockdep: add lockdep lock state defines
>   ath10k: detect conf_mutex held ath10k_drain_tx() calls

Thanks!

Kalle Valo March 1, 2021, 8:45 a.m. UTC | #2

Peter Zijlstra <[e-mail]> writes:

> On Fri, Feb 26, 2021 at 05:06:57PM -0700, Shuah Khan wrote:
>> Shuah Khan (3):
>>   lockdep: add lockdep_assert_not_held()
>>   lockdep: add lockdep lock state defines
>>   ath10k: detect conf_mutex held ath10k_drain_tx() calls
>
> Thanks!

Via which tree should these go?

Peter Zijlstra March 1, 2021, 9:36 a.m. UTC | #3

On Mon, Mar 01, 2021 at 10:45:32AM +0200, Kalle Valo wrote:
> Peter Zijlstra <[e-mail]> writes:
> 
> > On Fri, Feb 26, 2021 at 05:06:57PM -0700, Shuah Khan wrote:
> >> Shuah Khan (3):
> >>   lockdep: add lockdep_assert_not_held()
> >>   lockdep: add lockdep lock state defines
> >>   ath10k: detect conf_mutex held ath10k_drain_tx() calls
> >
> > Thanks!
> 
> Via which tree should these go?

I've just queued the lot for locking/core, which will show up in tip
when the robots don't hate on it.

Does that work for you?

Kalle Valo March 1, 2021, 11:02 a.m. UTC | #4

Peter Zijlstra <[e-mail]> writes:

> On Mon, Mar 01, 2021 at 10:45:32AM +0200, Kalle Valo wrote:
>> Peter Zijlstra <[e-mail]> writes:
>> 
>> > On Fri, Feb 26, 2021 at 05:06:57PM -0700, Shuah Khan wrote:
>> >> Shuah Khan (3):
>> >>   lockdep: add lockdep_assert_not_held()
>> >>   lockdep: add lockdep lock state defines
>> >>   ath10k: detect conf_mutex held ath10k_drain_tx() calls
>> >
>> > Thanks!
>> 
>> Via which tree should these go?
>
> I've just queued the lot for locking/core, which will show up in tip
> when the robots don't hate on it.
>
> Does that work for you?

That's perfect, thanks! Just making sure that the patches don't get
lost.

Shuah Khan March 1, 2021, 4:04 p.m. UTC | #5

On 3/1/21 4:02 AM, Kalle Valo wrote:
> Peter Zijlstra <[e-mail]> writes:
> 
>> On Mon, Mar 01, 2021 at 10:45:32AM +0200, Kalle Valo wrote:
>>> Peter Zijlstra <[e-mail]> writes:
>>>
>>>> On Fri, Feb 26, 2021 at 05:06:57PM -0700, Shuah Khan wrote:
>>>>> Shuah Khan (3):
>>>>>    lockdep: add lockdep_assert_not_held()
>>>>>    lockdep: add lockdep lock state defines
>>>>>    ath10k: detect conf_mutex held ath10k_drain_tx() calls
>>>>
>>>> Thanks!
>>>
>>> Via which tree should these go?
>>
>> I've just queued the lot for locking/core, which will show up in tip
>> when the robots don't hate on it.
>>
>> Does that work for you?
> 
> That's perfect, thanks! Just making sure that the patches don't get
> lost.
> 

Awesome. Thank you.

thanks,
-- Shuah