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From: Byungchul Park <byungchul@sk.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org, kernel_team@skhynix.com,
	torvalds@linux-foundation.org, damien.lemoal@opensource.wdc.com,
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	42.hyeyoo@gmail.com, chris.p.wilson@intel.com,
	gwan-gyeong.mun@intel.com, max.byungchul.park@gmail.com,
	boqun.feng@gmail.com, longman@redhat.com, hdanton@sina.com,
	her0gyugyu@gmail.com
Subject: Re: [PATCH v11 14/26] locking/lockdep, cpu/hotplus: Use a weaker annotation in AP thread
Date: Tue, 30 Jan 2024 11:58:36 +0900	[thread overview]
Message-ID: <20240130025836.GA49173@system.software.com> (raw)
In-Reply-To: <87il3ggfz9.ffs@tglx>

On Fri, Jan 26, 2024 at 06:30:02PM +0100, Thomas Gleixner wrote:
> On Wed, Jan 24 2024 at 20:59, Byungchul Park wrote:
> 
> Why is lockdep in the subsystem prefix here? You are changing the CPU
> hotplug (not hotplus) code, right?
> 
> > cb92173d1f0 ("locking/lockdep, cpu/hotplug: Annotate AP thread") was
> > introduced to make lockdep_assert_cpus_held() work in AP thread.
> >
> > However, the annotation is too strong for that purpose. We don't have to
> > use more than try lock annotation for that.
> 
> This lacks a proper explanation why this is too strong.
> 
> > Furthermore, now that Dept was introduced, false positive alarms was
> > reported by that. Replaced it with try lock annotation.
> 
> I still have zero idea what this is about.

1. can track PG_locked that is a potential deadlock trigger.

   https://lore.kernel.org/lkml/1674268856-31807-1-git-send-email-byungchul.park@lge.com/

2. can track any waits/events e.g. wait_for_xxx(), dma fence and so on.

3. easy to annotate using dept_wait() on waits, dept_event() on events.

4. track read lock better way instead of the ugly way, by assinging wait
   or event annotations onto read lock and write lock. For instrance, a
   read lock is annotated as a potential waiter for its write unlock,
   and a write lock is annotated as a potential waiter for either write
   unlock or read unlock.

I'd like to remove unnecessary complexity on deadlock detection and add
additional functionality by making it do what the type of tool exactly
should do.

	Byungchul

> Thanks,
> 
>         tglx

  parent reply	other threads:[~2024-01-30  2:58 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-01-24 11:59 [PATCH v11 00/26] DEPT(Dependency Tracker) Byungchul Park
2024-01-24 11:59 ` [PATCH v11 01/26] llist: Move llist_{head,node} definition to types.h Byungchul Park
2024-01-24 11:59 ` [PATCH v11 02/26] dept: Implement Dept(Dependency Tracker) Byungchul Park
2024-01-24 11:59 ` [PATCH v11 03/26] dept: Add single event dependency tracker APIs Byungchul Park
2024-01-24 11:59 ` [PATCH v11 04/26] dept: Add lock " Byungchul Park
2024-01-24 11:59 ` [PATCH v11 05/26] dept: Tie to Lockdep and IRQ tracing Byungchul Park
2024-01-28 13:10   ` kernel test robot
2024-01-28 15:58   ` kernel test robot
2024-01-24 11:59 ` [PATCH v11 06/26] dept: Add proc knobs to show stats and dependency graph Byungchul Park
2024-01-24 11:59 ` [PATCH v11 07/26] dept: Apply sdt_might_sleep_{start,end}() to wait_for_completion()/complete() Byungchul Park
2024-01-24 11:59 ` [PATCH v11 08/26] dept: Apply sdt_might_sleep_{start,end}() to swait Byungchul Park
2024-01-24 11:59 ` [PATCH v11 09/26] dept: Apply sdt_might_sleep_{start,end}() to waitqueue wait Byungchul Park
2024-01-24 11:59 ` [PATCH v11 10/26] dept: Apply sdt_might_sleep_{start,end}() to hashed-waitqueue wait Byungchul Park
2024-01-24 11:59 ` [PATCH v11 11/26] dept: Distinguish each syscall context from another Byungchul Park
2024-01-24 11:59 ` [PATCH v11 12/26] dept: Distinguish each work " Byungchul Park
2024-01-24 11:59 ` [PATCH v11 13/26] dept: Add a mechanism to refill the internal memory pools on running out Byungchul Park
2024-01-24 11:59 ` [PATCH v11 14/26] locking/lockdep, cpu/hotplus: Use a weaker annotation in AP thread Byungchul Park
2024-01-26 17:30   ` Thomas Gleixner
2024-01-29  4:20     ` Byungchul Park
2024-01-30  2:58     ` Byungchul Park [this message]
2024-02-12 15:16       ` Thomas Gleixner
2024-02-13  1:18         ` Byungchul Park
2024-01-24 11:59 ` [PATCH v11 15/26] dept: Apply sdt_might_sleep_{start,end}() to dma fence wait Byungchul Park
2024-01-24 11:59 ` [PATCH v11 16/26] dept: Track timeout waits separately with a new Kconfig Byungchul Park
2024-01-24 11:59 ` [PATCH v11 17/26] dept: Apply timeout consideration to wait_for_completion()/complete() Byungchul Park
2024-01-24 11:59 ` [PATCH v11 18/26] dept: Apply timeout consideration to swait Byungchul Park
2024-01-24 11:59 ` [PATCH v11 19/26] dept: Apply timeout consideration to waitqueue wait Byungchul Park
2024-01-24 11:59 ` [PATCH v11 20/26] dept: Apply timeout consideration to hashed-waitqueue wait Byungchul Park
2024-01-24 11:59 ` [PATCH v11 21/26] dept: Apply timeout consideration to dma fence wait Byungchul Park
2024-01-24 11:59 ` [PATCH v11 22/26] dept: Record the latest one out of consecutive waits of the same class Byungchul Park
2024-01-24 11:59 ` [PATCH v11 23/26] dept: Make Dept able to work with an external wgen Byungchul Park
2024-01-24 11:59 ` [PATCH v11 24/26] dept: Track PG_locked with dept Byungchul Park
2024-01-24 11:59 ` [PATCH v11 25/26] dept: Print event context requestor's stacktrace on report Byungchul Park
2024-01-28 14:44   ` kernel test robot
2024-01-24 11:59 ` [PATCH v11 26/26] locking/lockdep, fs/jbd2: Use a weaker annotation in journal handling Byungchul Park

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