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Date:   Wed, 2 Mar 2022 04:53:41 +0000
From:   Hyeonggon Yoo <42.hyeyoo@gmail.com>
To:     Byungchul Park <byungchul.park@lge.com>
Cc:     torvalds@linux-foundation.org, damien.lemoal@opensource.wdc.com,
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Subject: Re: [PATCH v3 00/21] DEPT(Dependency Tracker)
Message-ID: <Yh74VbNZZt35wHZD@ip-172-31-19-208.ap-northeast-1.compute.internal>
References: <1646042220-28952-1-git-send-email-byungchul.park@lge.com>
 <Yh70VkRkUfwIjPWv@ip-172-31-19-208.ap-northeast-1.compute.internal>
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On Wed, Mar 02, 2022 at 04:36:38AM +0000, Hyeonggon Yoo wrote:
> On Mon, Feb 28, 2022 at 06:56:39PM +0900, Byungchul Park wrote:
> > I didn't want to bother you so I was planning to send the next spin
> > after making more progress. However, PATCH v2 reports too many false
> > positives because Dept tracked the bit_wait_table[] wrong way - I
> > apologize for that. So I decided to send PATCH v3 first before going
> > further for those who want to run Dept for now.
> > 
> > There might still be some false positives but not overwhelming.
> >
> 
> Hello Byungchul, I'm running DEPT v3 on my system
> and I see report below.
> 
> Looking at the kmemleak code and comment, I think
> kmemleak tried to avoid lockdep recursive warning
> but detected by DEPT?
>

Forgot to include another warning caused by DEPT.

And comment below might be useful for debugging:

in kmemleak.c:
  43  * Locks and mutexes are acquired/nested in the following order:
  44  *
  45  *   scan_mutex [-> object->lock] -> kmemleak_lock -> other_object->lock (SINGLE_DEPTH_NESTING)
  46  *
  47  * No kmemleak_lock and object->lock nesting is allowed outside scan_mutex
  48  * regions.

===================================================
DEPT: Circular dependency has been detected.
5.17.0-rc1+ #1 Tainted: G        W        
---------------------------------------------------
summary
---------------------------------------------------
*** DEADLOCK ***

context A
    [S] __raw_spin_lock_irqsave(&object->lock:0)
    [W] __raw_spin_lock_irqsave(kmemleak_lock:0)
    [E] spin_unlock(&object->lock:0)

context B
    [S] __raw_spin_lock_irqsave(kmemleak_lock:0)
    [W] _raw_spin_lock_nested(&object->lock:0)
    [E] spin_unlock(kmemleak_lock:0)

[S]: start of the event context
[W]: the wait blocked
[E]: the event not reachable

---------------------------------------------------
context A's detail
---------------------------------------------------
context A
    [S] __raw_spin_lock_irqsave(&object->lock:0)
    [W] __raw_spin_lock_irqsave(kmemleak_lock:0)
    [E] spin_unlock(&object->lock:0)

[S] __raw_spin_lock_irqsave(&object->lock:0):
[<ffffffc00810302c>] scan_gray_list+0x84/0x13c
stacktrace:
      dept_ecxt_enter+0x88/0xf4
      _raw_spin_lock_irqsave+0xf0/0x1c4
      scan_gray_list+0x84/0x13c
      kmemleak_scan+0x2d8/0x54c
      kmemleak_scan_thread+0xac/0xd4
      kthread+0xd4/0xe4
      ret_from_fork+0x10/0x20

[W] __raw_spin_lock_irqsave(kmemleak_lock:0):
[<ffffffc008102ebc>] scan_block+0x3c/0x128
stacktrace:
      __dept_wait+0x8c/0xa4
      dept_wait+0x6c/0x88
      _raw_spin_lock_irqsave+0xb8/0x1c4
      scan_block+0x3c/0x128
      scan_gray_list+0xc4/0x13c
      kmemleak_scan+0x2d8/0x54c
      kmemleak_scan_thread+0xac/0xd4
      kthread+0xd4/0xe4
      ret_from_fork+0x10/0x20

[E] spin_unlock(&object->lock:0):
[<ffffffc008102ee0>] scan_block+0x60/0x128

---------------------------------------------------
context B's detail
---------------------------------------------------
context B
    [S] __raw_spin_lock_irqsave(kmemleak_lock:0)
    [W] _raw_spin_lock_nested(&object->lock:0)
    [E] spin_unlock(kmemleak_lock:0)

[S] __raw_spin_lock_irqsave(kmemleak_lock:0):
[<ffffffc008102ebc>] scan_block+0x3c/0x128
stacktrace:
      dept_ecxt_enter+0x88/0xf4
      _raw_spin_lock_irqsave+0xf0/0x1c4
      scan_block+0x3c/0x128
      kmemleak_scan+0x19c/0x54c
      kmemleak_scan_thread+0xac/0xd4
      kthread+0xd4/0xe4
      ret_from_fork+0x10/0x20

[W] _raw_spin_lock_nested(&object->lock:0):
[<ffffffc008102f34>] scan_block+0xb4/0x128
stacktrace:
      dept_wait+0x74/0x88
      _raw_spin_lock_nested+0xa8/0x1b0
      scan_block+0xb4/0x128
      kmemleak_scan+0x19c/0x54c
      kmemleak_scan_thread+0xac/0xd4
      kthread+0xd4/0xe4
      ret_from_fork+0x10/0x20
[E] spin_unlock(kmemleak_lock:0):
[<ffffffc008102ee0>] scan_block+0x60/0x128
stacktrace:
      dept_event+0x7c/0xfc
      _raw_spin_unlock_irqrestore+0x8c/0x120
      scan_block+0x60/0x128
      kmemleak_scan+0x19c/0x54c
      kmemleak_scan_thread+0xac/0xd4
      kthread+0xd4/0xe4
      ret_from_fork+0x10/0x20
---------------------------------------------------
information that might be helpful
---------------------------------------------------
CPU: 1 PID: 38 Comm: kmemleak Tainted: G        W         5.17.0-rc1+ #1
Hardware name: linux,dummy-virt (DT)
Call trace:
 dump_backtrace.part.0+0x9c/0xc4
 show_stack+0x14/0x28
 dump_stack_lvl+0x9c/0xcc
 dump_stack+0x14/0x2c
 print_circle+0x2d4/0x438
 cb_check_dl+0x6c/0x70
 bfs+0xc0/0x168
 add_dep+0x88/0x11c
 add_wait+0x2d0/0x2dc
 __dept_wait+0x8c/0xa4
 dept_wait+0x6c/0x88
 _raw_spin_lock_irqsave+0xb8/0x1c4
 scan_block+0x3c/0x128
 scan_gray_list+0xc4/0x13c
 kmemleak_scan+0x2d8/0x54c
 kmemleak_scan_thread+0xac/0xd4
 kthread+0xd4/0xe4
 ret_from_fork+0x10/0x20

> ===================================================
> DEPT: Circular dependency has been detected.
> 5.17.0-rc1+ #1 Tainted: G        W
> ---------------------------------------------------
> summary
> ---------------------------------------------------
> *** AA DEADLOCK ***
> 
> context A
>     [S] __raw_spin_lock_irqsave(&object->lock:0)
>     [W] _raw_spin_lock_nested(&object->lock:0)
>     [E] spin_unlock(&object->lock:0)
> 
> [S]: start of the event context
> [W]: the wait blocked
> [E]: the event not reachable
> ---------------------------------------------------
> context A's detail
> ---------------------------------------------------
> context A
>     [S] __raw_spin_lock_irqsave(&object->lock:0)
>     [W] _raw_spin_lock_nested(&object->lock:0)
>     [E] spin_unlock(&object->lock:0)
> 
> [S] __raw_spin_lock_irqsave(&object->lock:0):
> [<ffffffc00810302c>] scan_gray_list+0x84/0x13c
> stacktrace:
>       dept_ecxt_enter+0x88/0xf4
>       _raw_spin_lock_irqsave+0xf0/0x1c4
>       scan_gray_list+0x84/0x13c
>       kmemleak_scan+0x2d8/0x54c
>       kmemleak_scan_thread+0xac/0xd4
>       kthread+0xd4/0xe4
>       ret_from_fork+0x10/0x20
> 
> [E] spin_unlock(&object->lock:0):
> [<ffffffc008102ee0>] scan_block+0x60/0x128
> ---------------------------------------------------
> information that might be helpful
> ---------------------------------------------------
> CPU: 1 PID: 38 Comm: kmemleak Tainted: G        W         5.17.0-rc1+ #1
> Hardware name: linux,dummy-virt (DT)
> Call trace:
>  dump_backtrace.part.0+0x9c/0xc4
>  show_stack+0x14/0x28
>  dump_stack_lvl+0x9c/0xcc
>  dump_stack+0x14/0x2c
>  print_circle+0x2d4/0x438
>  cb_check_dl+0x44/0x70
>  bfs+0x60/0x168
>  add_dep+0x88/0x11c
>  add_wait+0x2d0/0x2dc
>  __dept_wait+0x8c/0xa4
>  dept_wait+0x6c/0x88
>  _raw_spin_lock_nested+0xa8/0x1b0
>  scan_block+0xb4/0x128
>  scan_gray_list+0xc4/0x13c
>  kmemleak_scan+0x2d8/0x54c
>  kmemleak_scan_thread+0xac/0xd4
>  kthread+0xd4/0xe4
>  ret_from_fork+0x10/0x20
>
[...]

--
Thank you, You are awesome!
Hyeonggon :-)