Re: [PATCH hazptr v3 0/4] Hazard pointer updates

[Bradley Morgan]

On 26 October 2026 12:01:18 GMT, Kai Ma <kai.ma1@xxxxxxxxxx> wrote:
>"Paul E. McKenney" <paulmck@xxxxxxxxxx> writes:
>
>> On Sun, Oct 11, 2026 at 03:48:46PM -0400, Mathieu Desnoyers wrote:
>>> Hi Paul,
>>> 
>>> This series applies on top of "hazptr: handle NULL address in
>>> hazptr_detach" you have in your rcu dev tree.
>>> 
>>> This first patch addresses a race identified by Boqun Feng in the
>>> two-phase wildcard scheme. (no change since the last series)
>>> 
>>> Patches 2-3 are prerequisites for using ptr_eq() in the 4th patch.
>>> Those were discussed at length in a prior version of hazard pointer
>>> patches.
>>> 
>>> Since the last series, I have renamed ptreq.h to ptr_eq.h, addressing
>>> the feedback received from Boqun and Gary.
>>> 
>>> Patch 4 introduces a "try acquire" helper to allow the fast path
>>> to not rely on wildcards, while keeping the wildcard forward
>>> progress guarantees in the acquire slow path, used on fast path
>>> failure.
>>
>> I have pulled this in for additional review and testing, thank you!
>> (With Bradley's Reviewed-by on 4/4.)  Still subject to rebase, which
>means
>> that I can easily replace it with an updated series from you, if you
>> wish.
>
>Hi Paul, Mathieu, and everyone,
>
>I've been following the hazard pointer work and have done some testing
>on earlier versions. I'd be interested in getting more involved,
>particularly in concurrency correctness testing.
>
>If there are WIP patches or early design discussions where additional
>review or testing would be useful, could you please CC me? I'd
>appreciate the opportunity to get involved earlier and help identify
>potential concurrency issues.

Thanks for taking this job up, what you could do, is make Linus happy, if
that makes sense.

https://lore.kernel.org/all/CAHk-=wjyniJy-CX1muCrsZp-i-sLGRYeRYEPN7sw9orRZUCwag@xxxxxxxxxxxxxx/

>
>Thanks,
>Kai
>
>> But in the meantime, some additional testing.  ;-)
>>
>> 							Thanx, Paul
>>
>>> Thanks,
>>> 
>>> Mathieu
>>> 
>>> Mathieu Desnoyers (4):
>>>   hazptr: Fix two-phase hazptr_synchronize race with detach
>>>   ptr_eq.h: Introduce ptr_eq() to preserve address dependency
>>>   Documentation: RCU: Refer to ptr_eq()
>>>   hazptr: Introduce "try acquire" fast path, fallback to overflow list
>>> 
>>> Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
>>> Cc: Boqun Feng <boqun@xxxxxxxxxx>
>>> Cc: Bradley Morgan <brads@xxxxxxxxxxxxxx>
>>> Cc: Gary Guo <gary@xxxxxxxxxxx>
>>> Cc: <rcu@xxxxxxxxxxxxxxx>
>>> Cc: <lkmm@xxxxxxxxxxxxxxx>
>>> Cc: Lian Wang <lianux.mm@xxxxxxxxx>
>>> Cc: Kunwu Chan <kunwu.chan@xxxxxxxxx>
>>> 
>>>  Documentation/RCU/rcu_dereference.rst |  38 +++++++-
>>>  arch/x86/include/asm/ptr_eq.h         |  16 +++
>>>  include/asm-generic/Kbuild            |   1 +
>>>  include/asm-generic/ptr_eq.h          |  16 +++
>>>  include/linux/hazptr.h                |  48 +++++----
>>>  include/linux/ptr_eq.h                |  63 ++++++++++++
>>>  kernel/hazptr.c                       | 135 +++++++++++++++-----------
>>>  7 files changed, 237 insertions(+), 80 deletions(-)
>>>  create mode 100644 arch/x86/include/asm/ptr_eq.h
>>>  create mode 100644 include/asm-generic/ptr_eq.h
>>>  create mode 100644 include/linux/ptr_eq.h
>>> 
>>> -- 
>>> 2.43.0
>>> 
>
>

--- Thanks!