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Message-ID: <20220316043212.GA5715@X58A-UD3R>
Date: Wed, 16 Mar 2022 13:32:13 +0900
From: Byungchul Park <byungchul.park@....com>
To: Hyeonggon Yoo <42.hyeyoo@...il.com>
Cc: torvalds@...ux-foundation.org, damien.lemoal@...nsource.wdc.com,
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Subject: Re: [PATCH v4 00/24] DEPT(Dependency Tracker)
On Sat, Mar 12, 2022 at 01:53:26AM +0000, Hyeonggon Yoo wrote:
> On Fri, Mar 04, 2022 at 04:06:19PM +0900, Byungchul Park wrote:
> > Hi Linus and folks,
> >
> > I've been developing a tool for detecting deadlock possibilities by
> > tracking wait/event rather than lock(?) acquisition order to try to
> > cover all synchonization machanisms. It's done on v5.17-rc1 tag.
> >
> > https://github.com/lgebyungchulpark/linux-dept/commits/dept1.14_on_v5.17-rc1
> >
>
> Small feedback unrelated to thread:
> I'm not sure "Need to expand the ring buffer" is something to call
> WARN(). Is this stack trace useful for something?
> ========
>
> Hello Byungchul. These are two warnings of DEPT on system.
Hi Hyeonggon,
Could you run scripts/decode_stacktrace.sh and share the result instead
of the raw format below if the reports still appear with PATCH v5? It'd
be appreciated (:
https://lkml.org/lkml/2022/3/15/1277
(or https://github.com/lgebyungchulpark/linux-dept/commits/dept1.18_on_v5.17-rc7)
Thank you very much!
--
Byungchul
> Both cases look similar.
>
> In what case DEPT says (unknown)?
> I'm not sure we can properly debug this.
>
> ===================================================
> DEPT: Circular dependency has been detected.
> 5.17.0-rc1+ #3 Tainted: G W
> ---------------------------------------------------
> summary
> ---------------------------------------------------
> *** AA DEADLOCK ***
>
> context A
> [S] (unknown)(&vfork:0)
> [W] wait_for_completion_killable(&vfork:0)
> [E] complete(&vfork:0)
>
> [S]: start of the event context
> [W]: the wait blocked
> [E]: the event not reachable
> ---------------------------------------------------
> context A's detail
> ---------------------------------------------------
> context A
> [S] (unknown)(&vfork:0)
> [W] wait_for_completion_killable(&vfork:0)
> [E] complete(&vfork:0)
>
> [S] (unknown)(&vfork:0):
> (N/A)
>
> [W] wait_for_completion_killable(&vfork:0):
> [<ffffffc00802204c>] kernel_clone+0x25c/0x2b8
> stacktrace:
> dept_wait+0x74/0x88
> wait_for_completion_killable+0x60/0xa0
> kernel_clone+0x25c/0x2b8
> __do_sys_clone+0x5c/0x74
> __arm64_sys_clone+0x18/0x20
> invoke_syscall.constprop.0+0x78/0xc4
> do_el0_svc+0x98/0xd0
> el0_svc+0x44/0xe4
> el0t_64_sync_handler+0xb0/0x12c
> el0t_64_sync+0x158/0x15c
>
> [E] complete(&vfork:0):
> [<ffffffc00801f49c>] mm_release+0x7c/0x90
> stacktrace:
> dept_event+0xe0/0x100
> complete+0x48/0x98
> mm_release+0x7c/0x90
> exit_mm_release+0xc/0x14
> do_exit+0x1b4/0x81c
> do_group_exit+0x30/0x9c
> __wake_up_parent+0x0/0x24
> invoke_syscall.constprop.0+0x78/0xc4
> do_el0_svc+0x98/0xd0
> el0_svc+0x44/0xe4
> el0t_64_sync_handler+0xb0/0x12c
> el0t_64_sync+0x158/0x15c
> ---------------------------------------------------
> information that might be helpful
> ---------------------------------------------------
> CPU: 6 PID: 229 Comm: start-stop-daem Tainted: G W 5.17.0-rc1+ #3
> 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
> do_event.constprop.0+0x19c/0x2c0
> dept_event+0xe0/0x100
> complete+0x48/0x98
> mm_release+0x7c/0x90
> exit_mm_release+0xc/0x14
> do_exit+0x1b4/0x81c
> do_group_exit+0x30/0x9c
> __wake_up_parent+0x0/0x24
> invoke_syscall.constprop.0+0x78/0xc4
> do_el0_svc+0x98/0xd0
> el0_svc+0x44/0xe4
> el0t_64_sync_handler+0xb0/0x12c
> el0t_64_sync+0x158/0x15c
>
>
>
>
> ===================================================
> DEPT: Circular dependency has been detected.
> 5.17.0-rc1+ #3 Tainted: G W
> ---------------------------------------------------
> summary
> ---------------------------------------------------
> *** AA DEADLOCK ***
>
> context A
> [S] (unknown)(&try_completion:0)
> [W] wait_for_completion_timeout(&try_completion:0)
> [E] complete(&try_completion:0)
>
> [S]: start of the event context
> [W]: the wait blocked
> [E]: the event not reachable
> ---------------------------------------------------
> context A's detail
> ---------------------------------------------------
> context A
> [S] (unknown)(&try_completion:0)
> [W] wait_for_completion_timeout(&try_completion:0)
> [E] complete(&try_completion:0)
>
> [S] (unknown)(&try_completion:0):
> (N/A)
>
> [W] wait_for_completion_timeout(&try_completion:0):
> [<ffffffc008166bf4>] kunit_try_catch_run+0xb4/0x160
> stacktrace:
> dept_wait+0x74/0x88
> wait_for_completion_timeout+0x64/0xa0
> kunit_try_catch_run+0xb4/0x160
> kunit_test_try_catch_successful_try_no_catch+0x3c/0x98
> kunit_try_run_case+0x9c/0xa0
> kunit_generic_run_threadfn_adapter+0x1c/0x28
> kthread+0xd4/0xe4
> ret_from_fork+0x10/0x20
>
> [E] complete(&try_completion:0):
> [<ffffffc00803dce4>] kthread_complete_and_exit+0x18/0x20
> stacktrace:
> dept_event+0xe0/0x100
> complete+0x48/0x98
> kthread_complete_and_exit+0x18/0x20
> kunit_try_catch_throw+0x0/0x1c
> kthread+0xd4/0xe4
> ret_from_fork+0x10/0x20
>
> ---------------------------------------------------
> information that might be helpful
> ---------------------------------------------------
> CPU: 15 PID: 132 Comm: kunit_try_catch Tainted: G W 5.17.0-rc1+ #3
> 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
> do_event.constprop.0+0x19c/0x2c0
> dept_event+0xe0/0x100
> complete+0x48/0x98
> kthread_complete_and_exit+0x18/0x20
> kunit_try_catch_throw+0x0/0x1c
> kthread+0xd4/0xe4
> ret_from_fork+0x10/0x20
>
>
> > Benifit:
> >
> > 0. Works with all lock primitives.
> > 1. Works with wait_for_completion()/complete().
> > 2. Works with 'wait' on PG_locked.
> > 3. Works with 'wait' on PG_writeback.
> > 4. Works with swait/wakeup.
> > 5. Works with waitqueue.
> > 6. Multiple reports are allowed.
> > 7. Deduplication control on multiple reports.
> > 8. Withstand false positives thanks to 6.
> > 9. Easy to tag any wait/event.
> >
> > Future work:
>
> [...]
>
> > --
> > 1.9.1
> >
>
> --
> Thank you, You are awesome!
> Hyeonggon :-)
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