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From: "Coelho, Luciano" <luciano.coelho@intel.com>
To: "jikos@kernel.org" <jikos@kernel.org>,
        "Zhang, Rui" <rui.zhang@intel.com>,
        "kvalo@codeaurora.org" <kvalo@codeaurora.org>,
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        "Sharon, Sara" <sara.sharon@intel.com>,
        "Berg, Johannes" <johannes.berg@intel.com>,
        "Grumbach, Emmanuel" <emmanuel.grumbach@intel.com>
CC: linuxwifi <linuxwifi@intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
        "Weinehall, David" <david.weinehall@intel.com>
Subject: Re: [linuxwifi] x86/thermal: AB-BA dependency between mvm->mutex
 and tz->lock
Thread-Topic: [linuxwifi] x86/thermal: AB-BA dependency between mvm->mutex
 and tz->lock
Thread-Index: AQHTDDhx/AJKrrLfQ0u/E+w0aR++lqJyULKA
Date: Thu, 3 Aug 2017 09:43:26 +0000
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         <alpine.LSU.2.20.1708031107230.30597@cbobk.fhfr.pm>
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On Thu, 2017-08-03 at 11:10 +0200, Jiri Kosina wrote:
> On Mon, 31 Jul 2017, Jiri Kosina wrote:
> 
> > Hi,
> > 
> > booting current Linus' tree, I'm seeing lockdep splat (see the end of this 
> > mail).
> > 
> > Apparently, there is AB-BA between tz->lock and mvm->mutex through the CPU 
> > hotplug lock.
> > 
> > The obivous depency is: thermal_zone_get_temp() acquires tz->lock, and 
> > then calls iwl_mvm_tzone_get_temp() (through tz->ops->get_temp() 
> > callback), which acquires mvm->mutex
> > 
> > The less obvious dependency is primarily caused by iwl_op_mode_mvm_start() 
> > allocating workqueue (#2 stacktrace) while holding mvm->mutex (which is 
> > broken, because that mutex is being taken also from CPU hotplug callback 
> > path, hence the AB-BA).
> 
> As the "central" part of the dependency is being added by iwlwifi driver 
> (_iwl_pcie_rx_init() allocating workqueue while holding 
> trans_pcie->mutex), I'm adding iwlwifi folks as well to CC.
> 
> > 
> >  ======================================================
> >  WARNING: possible circular locking dependency detected
> >  4.13.0-rc2-00110-g0b5477d #347 Not tainted
> >  ------------------------------------------------------
> >  modprobe/881 is trying to acquire lock:
> >   (&mvm->mutex){+.+.+.}, at: [<ffffffffc0c504d2>] iwl_mvm_tzone_get_temp+0x32/0x80 [iwlmvm]
> >  
> >  but task is already holding lock:
> >   (&tz->lock){+.+.+.}, at: [<ffffffff926a9351>] thermal_zone_get_temp+0x41/0x70
> >  
> >  which lock already depends on the new lock.
> > 
> >  
> >  the existing dependency chain (in reverse order) is:
> >  
> >  -> #5 (&tz->lock){+.+.+.}:
> >         lock_acquire+0xbd/0x220
> >         __mutex_lock+0x6e/0x900
> >         mutex_lock_nested+0x1b/0x20
> >         thermal_zone_get_temp+0x41/0x70
> >         thermal_zone_device_update+0x3c/0x280
> >         thermal_zone_device_register+0x3b8/0x610
> >         pkg_thermal_cpu_online+0x20b/0x284 [x86_pkg_temp_thermal]
> >         cpuhp_invoke_callback+0xac/0x900
> >         cpuhp_thread_fun+0x79/0x160
> >         smpboot_thread_fn+0x156/0x220
> >         kthread+0x114/0x150
> >         ret_from_fork+0x2a/0x40
> >  
> >  -> #4 (cpuhp_state){+.+.+.}:
> >         lock_acquire+0xbd/0x220
> >         cpuhp_issue_call+0xea/0x170
> >         __cpuhp_setup_state_cpuslocked+0x12a/0x190
> >         __cpuhp_setup_state+0x46/0xc0
> >         page_writeback_init+0x43/0x67
> >         pagecache_init+0x39/0x3c
> >         start_kernel+0x45a/0x4ae
> >         x86_64_start_reservations+0x24/0x26
> >         x86_64_start_kernel+0x13d/0x14c
> >         verify_cpu+0x0/0xf1
> >  
> >  -> #3 (cpuhp_state_mutex){+.+.+.}:
> >         lock_acquire+0xbd/0x220
> >         __mutex_lock+0x6e/0x900
> >         mutex_lock_nested+0x1b/0x20
> >         __cpuhp_setup_state_cpuslocked+0x4f/0x190
> >         __cpuhp_setup_state+0x46/0xc0
> >         page_alloc_init+0x28/0x30
> >         start_kernel+0x186/0x4ae
> >         x86_64_start_reservations+0x24/0x26
> >         x86_64_start_kernel+0x13d/0x14c
> >         verify_cpu+0x0/0xf1
> >  
> >  -> #2 (cpu_hotplug_lock.rw_sem){++++++}:
> >         lock_acquire+0xbd/0x220
> >         cpus_read_lock+0x46/0x90
> >         apply_workqueue_attrs+0x17/0x50
> >         __alloc_workqueue_key+0x195/0x4d0
> >         _iwl_pcie_rx_init+0x384/0x390 [iwlwifi]
> >         iwl_pcie_rx_init+0x1e/0x380 [iwlwifi]
> >         iwl_trans_pcie_start_fw+0x295/0x6f0 [iwlwifi]
> >         iwl_mvm_load_ucode_wait_alive+0xe7/0x390 [iwlmvm]
> >         iwl_run_init_mvm_ucode+0x84/0x320 [iwlmvm]
> >         iwl_op_mode_mvm_start+0x964/0xd30 [iwlmvm]
> >         _iwl_op_mode_start.isra.9+0x47/0xa0 [iwlwifi]
> >         iwl_opmode_register+0xaa/0xd0 [iwlwifi]
> >         iwl_mvm_init+0x37/0x1000 [iwlmvm]
> >         do_one_initcall+0x51/0x1a9
> >         do_init_module+0x60/0x20e
> >         load_module+0x203f/0x2b50
> >         SYSC_finit_module+0x96/0xd0
> >         SyS_finit_module+0xe/0x10
> >         entry_SYSCALL_64_fastpath+0x23/0xc2
> >  
> >  -> #1 (&trans_pcie->mutex){+.+.+.}:
> >         lock_acquire+0xbd/0x220
> >         __mutex_lock+0x6e/0x900
> >         mutex_lock_nested+0x1b/0x20
> >         iwl_trans_pcie_start_fw+0x130/0x6f0 [iwlwifi]
> >         iwl_mvm_load_ucode_wait_alive+0xe7/0x390 [iwlmvm]
> >         iwl_run_init_mvm_ucode+0x84/0x320 [iwlmvm]
> >         iwl_op_mode_mvm_start+0x964/0xd30 [iwlmvm]
> >         _iwl_op_mode_start.isra.9+0x47/0xa0 [iwlwifi]
> >         iwl_opmode_register+0xaa/0xd0 [iwlwifi]
> >         iwl_mvm_init+0x37/0x1000 [iwlmvm]
> >         do_one_initcall+0x51/0x1a9
> >         do_init_module+0x60/0x20e
> >         load_module+0x203f/0x2b50
> >         SYSC_finit_module+0x96/0xd0
> >         SyS_finit_module+0xe/0x10
> >         entry_SYSCALL_64_fastpath+0x23/0xc2
> >  
> >  -> #0 (&mvm->mutex){+.+.+.}:
> >         __lock_acquire+0x13e1/0x1400
> >         lock_acquire+0xbd/0x220
> >         __mutex_lock+0x6e/0x900
> >         mutex_lock_nested+0x1b/0x20
> >         iwl_mvm_tzone_get_temp+0x32/0x80 [iwlmvm]
> >         thermal_zone_get_temp+0x51/0x70
> >         thermal_zone_device_update+0x3c/0x280
> >         thermal_zone_device_register+0x3b8/0x610
> >         iwl_mvm_thermal_initialize+0x1d1/0x3a0 [iwlmvm]
> >         iwl_op_mode_mvm_start+0xa1d/0xd30 [iwlmvm]
> >         _iwl_op_mode_start.isra.9+0x47/0xa0 [iwlwifi]
> >         iwl_opmode_register+0xaa/0xd0 [iwlwifi]
> >         iwl_mvm_init+0x37/0x1000 [iwlmvm]
> >         do_one_initcall+0x51/0x1a9
> >         do_init_module+0x60/0x20e
> >         load_module+0x203f/0x2b50
> >         SYSC_finit_module+0x96/0xd0
> >         SyS_finit_module+0xe/0x10
> >         entry_SYSCALL_64_fastpath+0x23/0xc2
> >  
> >  other info that might help us debug this:
> > 
> >  Chain exists of:
> >    &mvm->mutex --> cpuhp_state --> &tz->lock
> > 
> >   Possible unsafe locking scenario:
> > 
> >         CPU0                    CPU1
> >         ----                    ----
> >    lock(&tz->lock);
> >                                 lock(cpuhp_state);
> >                                 lock(&tz->lock);
> >    lock(&mvm->mutex);
> >  
> >   *** DEADLOCK ***
> > 
> >  2 locks held by modprobe/881:
> >   #0:  (&iwlwifi_opmode_table_mtx){+.+.+.}, at: [<ffffffffc0aa2df4>] iwl_opmode_register+0x24/0xd0 [iwlwifi]
> >   #1:  (&tz->lock){+.+.+.}, at: [<ffffffff926a9351>] thermal_zone_get_temp+0x41/0x70
> >  
> >  stack backtrace:
> >  CPU: 3 PID: 881 Comm: modprobe Not tainted 4.13.0-rc2-00110-g0b5477d #347
> >  Hardware name: LENOVO 20K5S22R00/20K5S22R00, BIOS R0IET38W (1.16 ) 05/31/2017
> >  Call Trace:
> >   dump_stack+0x85/0xc9
> >   print_circular_bug+0x1f9/0x207
> >   __lock_acquire+0x13e1/0x1400
> >   lock_acquire+0xbd/0x220
> >   ? iwl_mvm_tzone_get_temp+0x32/0x80 [iwlmvm]
> >   ? iwl_mvm_tzone_get_temp+0x32/0x80 [iwlmvm]
> >   __mutex_lock+0x6e/0x900
> >   ? iwl_mvm_tzone_get_temp+0x32/0x80 [iwlmvm]
> >   ? thermal_zone_get_temp+0x41/0x70
> >   ? iwl_mvm_tzone_get_temp+0x32/0x80 [iwlmvm]
> >   ? thermal_zone_get_temp+0x41/0x70
> >   ? find_held_lock+0x39/0xb0
> >   mutex_lock_nested+0x1b/0x20
> >   iwl_mvm_tzone_get_temp+0x32/0x80 [iwlmvm]
> >   thermal_zone_get_temp+0x51/0x70
> >   thermal_zone_device_update+0x3c/0x280
> >   thermal_zone_device_register+0x3b8/0x610
> >   iwl_mvm_thermal_initialize+0x1d1/0x3a0 [iwlmvm]
> >   iwl_op_mode_mvm_start+0xa1d/0xd30 [iwlmvm]
> >   _iwl_op_mode_start.isra.9+0x47/0xa0 [iwlwifi]
> >   iwl_opmode_register+0xaa/0xd0 [iwlwifi]
> >   iwl_mvm_init+0x37/0x1000 [iwlmvm]
> >   ? 0xffffffffc0c87000
> >   do_one_initcall+0x51/0x1a9
> >   ? rcu_read_lock_sched_held+0x98/0xa0
> >   ? kmem_cache_alloc_trace+0x2a5/0x340
> >   do_init_module+0x60/0x20e
> >   load_module+0x203f/0x2b50
> >   ? __symbol_put+0x50/0x50
> >   SYSC_finit_module+0x96/0xd0
> >   SyS_finit_module+0xe/0x10
> >   entry_SYSCALL_64_fastpath+0x23/0xc2
> >  RIP: 0033:0x7f2ef067cc89
> >  RSP: 002b:00007ffea2ea3d78 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
> >  RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f2ef067cc89
> >  RDX: 0000000000000000 RSI: 000000000041af06 RDI: 0000000000000001
> >  RBP: 0000000000000005 R08: 0000000000000000 R09: 000000000096b230
> >  R10: 0000000000000001 R11: 0000000000000246 R12: 00007ffea2ea2d80
> >  R13: 00007ffea2ea2d60 R14: 0000000000000005 R15: 000000000096f3c0
> >  thermal thermal_zone3: failed to read out thermal zone (-5)

CCing David Weinehall who also just reported this to me.

We'll check this ASAP.  Thanks for reporting!

--
Luca.