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Date: Thu, 10 Aug 2017 19:52:04 +0900
From: Byungchul Park <byungchul.park@lge.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: mingo@kernel.org, tglx@linutronix.de, walken@google.com,
        boqun.feng@gmail.com, kirill@shutemov.name,
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        akpm@linux-foundation.org, willy@infradead.org, npiggin@gmail.com,
        kernel-team@lge.com
Subject: Re: [PATCH v8 00/14] lockdep: Implement crossrelease feature
Message-ID: <20170810105204.GC20323@X58A-UD3R>
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On Thu, Aug 10, 2017 at 09:55:56AM +0900, Byungchul Park wrote:
> On Wed, Aug 09, 2017 at 05:50:59PM +0200, Peter Zijlstra wrote:
> > 
> > 
> > Heh, look what it does...
> 
> It does not happen in my machine..
> 
> I tihink it happens because of "Simplify xhlock ring buffer invalidation"
> patch of you.

I mis-understood your simplification patch. I think your patch works well
unless overwriting occurs - it doesn't work if overwriting occurs though.

Anyway, if crossrelease and lockdep report the following in a normal
condition, it would be a desirable result.

What do you think about the following report? Positive? Or negative?

> 
> First of all, could you reverse yours and check if it happens, too?
> If not, we have to think the simplification more.
> 
> BTW, does your patch consider the possibility that a worker and irqs can
> be nested? Is it no problem even in the case?
> 
> > 
> > 
> > 4======================================================
> > 4WARNING: possible circular locking dependency detected
> > 4.13.0-rc2-00317-gadc6764a3adf-dirty #797 Tainted: G        W      
> > 4------------------------------------------------------
> > 4startpar/582 is trying to acquire lock:
> > c (c(complete)&barr->donec){+.+.}c, at: [<ffffffff8110de4d>] flush_work+0x1fd/0x2c0
> > 4
> > but task is already holding lock:
> > c (clockc#3c){+.+.}c, at: [<ffffffff8122e866>] lru_add_drain_all_cpuslocked+0x46/0x1a0
> > 4
> > which lock already depends on the new lock.
> > 
> > 4
> > the existing dependency chain (in reverse order) is:
> > 
> > -> #4c (clockc#3c){+.+.}c:
> >        __lock_acquire+0x10a5/0x1100
> >        lock_acquire+0xea/0x1f0
> >        __mutex_lock+0x6c/0x960
> >        mutex_lock_nested+0x1b/0x20
> >        lru_add_drain_all_cpuslocked+0x46/0x1a0
> >        lru_add_drain_all+0x13/0x20
> >        SyS_mlockall+0xb8/0x1c0
> >        entry_SYSCALL_64_fastpath+0x23/0xc2
> > 
> > -> #3c (ccpu_hotplug_lock.rw_semc){++++}c:
> >        __lock_acquire+0x10a5/0x1100
> >        lock_acquire+0xea/0x1f0
> >        cpus_read_lock+0x2a/0x90
> >        kmem_cache_create+0x2a/0x1d0
> >        scsi_init_sense_cache+0xa0/0xc0
> >        scsi_add_host_with_dma+0x67/0x360
> >        isci_pci_probe+0x873/0xc90
> >        local_pci_probe+0x42/0xa0
> >        work_for_cpu_fn+0x14/0x20
> >        process_one_work+0x273/0x6b0
> >        worker_thread+0x21b/0x3f0
> >        kthread+0x147/0x180
> >        ret_from_fork+0x2a/0x40
> > 
> > -> #2c (cscsi_sense_cache_mutexc){+.+.}c:
> >        __lock_acquire+0x10a5/0x1100
> >        lock_acquire+0xea/0x1f0
> >        __mutex_lock+0x6c/0x960
> >        mutex_lock_nested+0x1b/0x20
> >        scsi_init_sense_cache+0x3d/0xc0
> >        scsi_add_host_with_dma+0x67/0x360
> >        isci_pci_probe+0x873/0xc90
> >        local_pci_probe+0x42/0xa0
> >        work_for_cpu_fn+0x14/0x20
> >        process_one_work+0x273/0x6b0
> >        worker_thread+0x21b/0x3f0
> >        kthread+0x147/0x180
> >        ret_from_fork+0x2a/0x40
> > 
> > -> #1c (c(&wfc.work)c){+.+.}c:
> >        process_one_work+0x244/0x6b0
> >        worker_thread+0x21b/0x3f0
> >        kthread+0x147/0x180
> >        ret_from_fork+0x2a/0x40
> >        0xffffffffffffffff
> > 
> > -> #0c (c(complete)&barr->donec){+.+.}c:
> >        check_prev_add+0x3be/0x700
> >        __lock_acquire+0x10a5/0x1100
> >        lock_acquire+0xea/0x1f0
> >        wait_for_completion+0x3b/0x130
> >        flush_work+0x1fd/0x2c0
> >        lru_add_drain_all_cpuslocked+0x158/0x1a0
> >        lru_add_drain_all+0x13/0x20
> >        SyS_mlockall+0xb8/0x1c0
> >        entry_SYSCALL_64_fastpath+0x23/0xc2
> > 
> > other info that might help us debug this:
> > 
> > Chain exists of:
> >   c(complete)&barr->donec --> ccpu_hotplug_lock.rw_semc --> clockc#3c
> > 
> >  Possible unsafe locking scenario:
> > 
> >        CPU0                    CPU1
> >        ----                    ----
> >   lock(clockc#3c);
> >                                lock(ccpu_hotplug_lock.rw_semc);
> >                                lock(clockc#3c);
> >   lock(c(complete)&barr->donec);
> > 
> >  *** DEADLOCK ***
> > 
> > 2 locks held by startpar/582:
> >  #0: c (ccpu_hotplug_lock.rw_semc){++++}c, at: [<ffffffff8122e9ce>] lru_add_drain_all+0xe/0x20
> >  #1: c (clockc#3c){+.+.}c, at: [<ffffffff8122e866>] lru_add_drain_all_cpuslocked+0x46/0x1a0
> > 
> > stack backtrace:
> > dCPU: 23 PID: 582 Comm: startpar Tainted: G        W       4.13.0-rc2-00317-gadc6764a3adf-dirty #797
> > dHardware name: Intel Corporation S2600GZ/S2600GZ, BIOS SE5C600.86B.02.02.0002.122320131210 12/23/2013
> > dCall Trace:
> > d dump_stack+0x86/0xcf
> > d print_circular_bug+0x203/0x2f0
> > d check_prev_add+0x3be/0x700
> > d ? add_lock_to_list.isra.30+0xc0/0xc0
> > d ? is_bpf_text_address+0x82/0xe0
> > d ? unwind_get_return_address+0x1f/0x30
> > d __lock_acquire+0x10a5/0x1100
> > d ? __lock_acquire+0x10a5/0x1100
> > d ? add_lock_to_list.isra.30+0xc0/0xc0
> > d lock_acquire+0xea/0x1f0
> > d ? flush_work+0x1fd/0x2c0
> > d wait_for_completion+0x3b/0x130
> > d ? flush_work+0x1fd/0x2c0
> > d flush_work+0x1fd/0x2c0
> > d ? flush_workqueue_prep_pwqs+0x1c0/0x1c0
> > d ? trace_hardirqs_on+0xd/0x10
> > d lru_add_drain_all_cpuslocked+0x158/0x1a0
> > d lru_add_drain_all+0x13/0x20
> > d SyS_mlockall+0xb8/0x1c0
> > d entry_SYSCALL_64_fastpath+0x23/0xc2
> > dRIP: 0033:0x7f818d2e54c7
> > dRSP: 002b:00007fffcce83798 EFLAGS: 00000246c ORIG_RAX: 0000000000000097
> > dRAX: ffffffffffffffda RBX: 0000000000000046 RCX: 00007f818d2e54c7
> > dRDX: 0000000000000000 RSI: 00007fffcce83650 RDI: 0000000000000003
> > dRBP: 000000000002c010 R08: 0000000000000000 R09: 0000000000000000
> > dR10: 0000000000000008 R11: 0000000000000246 R12: 000000000002d000
> > dR13: 000000000002c010 R14: 0000000000001000 R15: 00007f818d599b00