Noticed (only once so far) the below issue on renesas-drivers-2016-12-27-v4.10-rc1 with lockdep enabled. Anybody else seen it?
[ 2.520105]
[ 2.521598] ======================================================
[ 2.527771] [ INFO: possible circular locking dependency detected ]
[ 2.534033] 4.10.0-rc1-00012-g862fa6e-dirty #19 Not tainted
[ 2.539598] -------------------------------------------------------
[ 2.545857] swapper/0/1 is trying to acquire lock:
[ 2.550641] (&genpd->mlock){+.+.+.}, at: [<ffff0000085bf544>] genpd_lock_mtx+0x24/0x30
[ 2.558654]
[ 2.558654] but task is already holding lock:
[ 2.564479] (prepare_lock){+.+...}, at: [<ffff0000085021d4>] clk_prepare_lock+0x2c/0xe8
[ 2.572575]
[ 2.572575] which lock already depends on the new lock.
[ 2.572575]
[ 2.580745]
[ 2.580745] the existing dependency chain (in reverse order) is:
[ 2.588219]
[ 2.588219] -> #2 (prepare_lock){+.+...}:
[ 2.593702]
[ 2.593712] [<ffff00000812c7e8>] __lock_acquire+0x1608/0x1688
[ 2.601539]
[ 2.601544] [<ffff00000812cc44>] lock_acquire+0xcc/0x298
[ 2.608937]
[ 2.608945] [<ffff0000089a1120>] mutex_lock_nested+0x78/0x648
[ 2.616771]
[ 2.616775] [<ffff0000085021fc>] clk_prepare_lock+0x54/0xe8
[ 2.624428]
[ 2.624433] [<ffff0000085077bc>] __clk_create_clk.part.16+0x5c/0xb0
[ 2.632780]
[ 2.632784] [<ffff00000850858c>] __of_clk_get_from_provider+0x124/0x168
[ 2.641479]
[ 2.641483] [<ffff000008500e48>] __of_clk_get_by_name+0x108/0x120
[ 2.649656]
[ 2.649660] [<ffff000008500eec>] clk_get+0x3c/0x90
[ 2.656532]
[ 2.656535] [<ffff000008500630>] devm_clk_get+0x50/0xa8
[ 2.663842]
[ 2.663849] [<ffff00000885f550>] rsnd_adg_probe+0x98/0x590
[ 2.671415]
[ 2.671420] [<ffff00000885c0d8>] rsnd_probe+0xd8/0x5b8
[ 2.678639]
[ 2.678645] [<ffff0000085a6018>] platform_drv_probe+0x58/0xc0
[ 2.686471]
[ 2.686478] [<ffff0000085a34bc>] driver_probe_device+0x2c4/0x458
[ 2.694565]
[ 2.694568] [<ffff0000085a377c>] __driver_attach+0x12c/0x130
[ 2.702308]
[ 2.702312] [<ffff0000085a0e00>] bus_for_each_dev+0x70/0xb0
[ 2.709965]
[ 2.709969] [<ffff0000085a2bf8>] driver_attach+0x30/0x40
[ 2.717361]
[ 2.717365] [<ffff0000085a25d8>] bus_add_driver+0x250/0x2c0
[ 2.725017]
[ 2.725021] [<ffff0000085a4950>] driver_register+0x68/0x100
[ 2.732674]
[ 2.732677] [<ffff0000085a5f44>] __platform_driver_register+0x54/0x60
[ 2.741198]
[ 2.741207] [<ffff000008d8cecc>] rsnd_driver_init+0x18/0x20
[ 2.748860]
[ 2.748866] [<ffff0000080839ac>] do_one_initcall+0x44/0x138
[ 2.756519]
[ 2.756526] [<ffff000008d40d84>] kernel_init_freeable+0x1f8/0x298
[ 2.764700]
[ 2.764704] [<ffff00000899a498>] kernel_init+0x18/0x108
[ 2.772010]
[ 2.772013] [<ffff000008083710>] ret_from_fork+0x10/0x40
[ 2.779405]
[ 2.779405] -> #1 (of_clk_mutex){+.+.+.}:
[ 2.784888]
[ 2.784892] [<ffff00000812c7e8>] __lock_acquire+0x1608/0x1688
[ 2.792719]
[ 2.792722] [<ffff00000812cc44>] lock_acquire+0xcc/0x298
[ 2.800115]
[ 2.800119] [<ffff0000089a1120>] mutex_lock_nested+0x78/0x648
[ 2.807945]
[ 2.807948] [<ffff0000085084b4>] __of_clk_get_from_provider+0x4c/0x168
[ 2.816557]
[ 2.816560] [<ffff000008508600>] of_clk_get_from_provider+0x30/0x40
[ 2.824907]
[ 2.824912] [<ffff00000850f004>] cpg_mssr_attach_dev+0xcc/0x1e8
[ 2.832912]
[ 2.832915] [<ffff0000085bfe74>] genpd_add_device+0x104/0x228
[ 2.840742]
[ 2.840745] [<ffff0000085c135c>] genpd_dev_pm_attach+0xac/0x2d0
[ 2.848745]
[ 2.848752] [<ffff0000085aeb30>] dev_pm_domain_attach+0x20/0x30
[ 2.856753]
[ 2.856755] [<ffff0000085a5ffc>] platform_drv_probe+0x3c/0xc0
[ 2.864582]
[ 2.864586] [<ffff0000085a34bc>] driver_probe_device+0x2c4/0x458
[ 2.872673]
[ 2.872676] [<ffff0000085a377c>] __driver_attach+0x12c/0x130
[ 2.880416]
[ 2.880419] [<ffff0000085a0e00>] bus_for_each_dev+0x70/0xb0
[ 2.888073]
[ 2.888076] [<ffff0000085a2bf8>] driver_attach+0x30/0x40
[ 2.895469]
[ 2.895472] [<ffff0000085a25d8>] bus_add_driver+0x250/0x2c0
[ 2.903126]
[ 2.903130] [<ffff0000085a4950>] driver_register+0x68/0x100
[ 2.910783]
[ 2.910786] [<ffff0000085a5f44>] __platform_driver_register+0x54/0x60
[ 2.919307]
[ 2.919314] [<ffff000008d72b20>] rcar_gen3_phy_usb2_driver_init+0x18/0x20
[ 2.928182]
[ 2.928185] [<ffff0000080839ac>] do_one_initcall+0x44/0x138
[ 2.935838]
[ 2.935841] [<ffff000008d40d84>] kernel_init_freeable+0x1f8/0x298
[ 2.944015]
[ 2.944019] [<ffff00000899a498>] kernel_init+0x18/0x108
[ 2.951324]
[ 2.951327] [<ffff000008083710>] ret_from_fork+0x10/0x40
[ 2.958721]
[ 2.958721] -> #0 (&genpd->mlock){+.+.+.}:
[ 2.964289]
[ 2.964293] [<ffff000008129778>] print_circular_bug+0x80/0x2e0
[ 2.972206]
[ 2.972210] [<ffff00000812c810>] __lock_acquire+0x1630/0x1688
[ 2.980036]
[ 2.980040] [<ffff00000812cc44>] lock_acquire+0xcc/0x298
[ 2.987432]
[ 2.987436] [<ffff0000089a1120>] mutex_lock_nested+0x78/0x648
[ 2.995262]
[ 2.995265] [<ffff0000085bf544>] genpd_lock_mtx+0x24/0x30
[ 3.002744]
[ 3.002747] [<ffff0000085c1b70>] genpd_runtime_resume+0xe0/0x270
[ 3.010834]
[ 3.010838] [<ffff0000085b20b8>] __rpm_callback+0xe8/0x260
[ 3.018405]
[ 3.018407] [<ffff0000085b2268>] rpm_callback+0x38/0xa8
[ 3.025713]
[ 3.025716] [<ffff0000085b1cdc>] rpm_resume+0x4bc/0x710
[ 3.033021]
[ 3.033024] [<ffff0000085b1f94>] __pm_runtime_resume+0x64/0xa0
[ 3.040938]
[ 3.040945] [<ffff00000875dd3c>] rcar_i2c_master_xfer+0x4c/0x4b8
[ 3.049032]
[ 3.049036] [<ffff0000087530f4>] __i2c_transfer+0x13c/0x9a8
[ 3.056690]
[ 3.056693] [<ffff0000087539cc>] i2c_transfer+0x6c/0xf8
[ 3.063999]
[ 3.064002] [<ffff000008753c4c>] i2c_smbus_xfer_emulated+0x11c/0x528
[ 3.072436]
[ 3.072439] [<ffff000008754204>] i2c_smbus_xfer+0x1ac/0x8e0
[ 3.080092]
[ 3.080095] [<ffff000008754b2c>] i2c_smbus_read_byte_data+0x3c/0x50
[ 3.088442]
[ 3.088446] [<ffff00000850c71c>] cs2000_bset.isra.1+0x34/0x60
[ 3.096273]
[ 3.096277] [<ffff00000850c77c>] cs2000_enable_dev_config+0x34/0x60
[ 3.104624]
[ 3.104628] [<ffff00000850c810>] cs2000_enable+0x28/0xd0
[ 3.112020]
[ 3.112023] [<ffff0000085029f0>] clk_core_prepare+0xf0/0x410
[ 3.119762]
[ 3.119765] [<ffff0000085031f4>] clk_prepare+0x2c/0x58
[ 3.126984]
[ 3.126989] [<ffff00000885f440>] rsnd_adg_clk_control+0x58/0xd0
[ 3.134989]
[ 3.134993] [<ffff00000885f8c8>] rsnd_adg_probe+0x410/0x590
[ 3.142646]
[ 3.142649] [<ffff00000885c0d8>] rsnd_probe+0xd8/0x5b8
[ 3.149868]
[ 3.149871] [<ffff0000085a6018>] platform_drv_probe+0x58/0xc0
[ 3.157698]
[ 3.157702] [<ffff0000085a34bc>] driver_probe_device+0x2c4/0x458
[ 3.165790]
[ 3.165793] [<ffff0000085a377c>] __driver_attach+0x12c/0x130
[ 3.173533]
[ 3.173536] [<ffff0000085a0e00>] bus_for_each_dev+0x70/0xb0
[ 3.181189]
[ 3.181193] [<ffff0000085a2bf8>] driver_attach+0x30/0x40
[ 3.188585]
[ 3.188588] [<ffff0000085a25d8>] bus_add_driver+0x250/0x2c0
[ 3.196241]
[ 3.196245] [<ffff0000085a4950>] driver_register+0x68/0x100
[ 3.203898]
[ 3.203901] [<ffff0000085a5f44>] __platform_driver_register+0x54/0x60
[ 3.212422]
[ 3.212426] [<ffff000008d8cecc>] rsnd_driver_init+0x18/0x20
[ 3.220080]
[ 3.220083] [<ffff0000080839ac>] do_one_initcall+0x44/0x138
[ 3.227736]
[ 3.227739] [<ffff000008d40d84>] kernel_init_freeable+0x1f8/0x298
[ 3.235913]
[ 3.235916] [<ffff00000899a498>] kernel_init+0x18/0x108
[ 3.243222]
[ 3.243225] [<ffff000008083710>] ret_from_fork+0x10/0x40
[ 3.250618]
[ 3.250618] other info that might help us debug this:
[ 3.250618]
[ 3.258614] Chain exists of:
[ 3.258614] &genpd->mlock --> of_clk_mutex --> prepare_lock
[ 3.258614]
[ 3.268701] Possible unsafe locking scenario:
[ 3.268701]
[ 3.274613] CPU0 CPU1
[ 3.279135] ---- ----
[ 3.283656] lock(prepare_lock);
[ 3.286965] lock(of_clk_mutex);
[ 3.292792] lock(prepare_lock);
[ 3.298618] lock(&genpd->mlock);
[ 3.302014]
[ 3.302014] *** DEADLOCK ***
[ 3.302014]
[ 3.307928] 3 locks held by swapper/0/1:
[ 3.311842] #0: (&dev->mutex){......}, at: [<ffff0000085a36d0>] __driver_attach+0x80/0x130
[ 3.320278] #1: (&dev->mutex){......}, at: [<ffff0000085a36e0>] __driver_attach+0x90/0x130
[ 3.328714] #2: (prepare_lock){+.+...}, at: [<ffff0000085021d4>] clk_prepare_lock+0x2c/0xe8
[ 3.337237]
[ 3.337237] stack backtrace:
[ 3.341589] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.10.0-rc1-00012-g862fa6e-dirty #19
[ 3.349757] Hardware name: Renesas Salvator-X board based on r8a7795 (DT)
[ 3.356538] Call trace:
[ 3.358980] [<ffff00000808a4c0>] dump_backtrace+0x0/0x2a0
[ 3.364372] [<ffff00000808a784>] show_stack+0x24/0x30
[ 3.369419] [<ffff00000848daa4>] dump_stack+0xbc/0xf8
[ 3.374465] [<ffff0000081298f0>] print_circular_bug+0x1f8/0x2e0
[ 3.380378] [<ffff00000812c810>] __lock_acquire+0x1630/0x1688
[ 3.386118] [<ffff00000812cc44>] lock_acquire+0xcc/0x298
[ 3.391423] [<ffff0000089a1120>] mutex_lock_nested+0x78/0x648
[ 3.397162] [<ffff0000085bf544>] genpd_lock_mtx+0x24/0x30
[ 3.402553] [<ffff0000085c1b70>] genpd_runtime_resume+0xe0/0x270
[ 3.408552] [<ffff0000085b20b8>] __rpm_callback+0xe8/0x260
[ 3.414030] [<ffff0000085b2268>] rpm_callback+0x38/0xa8
[ 3.419248] [<ffff0000085b1cdc>] rpm_resume+0x4bc/0x710
[ 3.424466] [<ffff0000085b1f94>] __pm_runtime_resume+0x64/0xa0
[ 3.430293] [<ffff00000875dd3c>] rcar_i2c_master_xfer+0x4c/0x4b8
[ 3.436292] [<ffff0000087530f4>] __i2c_transfer+0x13c/0x9a8
[ 3.441857] [<ffff0000087539cc>] i2c_transfer+0x6c/0xf8
[ 3.447075] [<ffff000008753c4c>] i2c_smbus_xfer_emulated+0x11c/0x528
[ 3.453422] [<ffff000008754204>] i2c_smbus_xfer+0x1ac/0x8e0
[ 3.458987] [<ffff000008754b2c>] i2c_smbus_read_byte_data+0x3c/0x50
[ 3.465247] [<ffff00000850c71c>] cs2000_bset.isra.1+0x34/0x60
[ 3.470987] [<ffff00000850c77c>] cs2000_enable_dev_config+0x34/0x60
[ 3.477246] [<ffff00000850c810>] cs2000_enable+0x28/0xd0
[ 3.482550] [<ffff0000085029f0>] clk_core_prepare+0xf0/0x410
[ 3.488202] [<ffff0000085031f4>] clk_prepare+0x2c/0x58
[ 3.493334] [<ffff00000885f440>] rsnd_adg_clk_control+0x58/0xd0
[ 3.499246] [<ffff00000885f8c8>] rsnd_adg_probe+0x410/0x590
[ 3.504812] [<ffff00000885c0d8>] rsnd_probe+0xd8/0x5b8
[ 3.509942] [<ffff0000085a6018>] platform_drv_probe+0x58/0xc0
[ 3.515682] [<ffff0000085a34bc>] driver_probe_device+0x2c4/0x458
[ 3.521681] [<ffff0000085a377c>] __driver_attach+0x12c/0x130
[ 3.527333] [<ffff0000085a0e00>] bus_for_each_dev+0x70/0xb0
[ 3.532899] [<ffff0000085a2bf8>] driver_attach+0x30/0x40
[ 3.538203] [<ffff0000085a25d8>] bus_add_driver+0x250/0x2c0
[ 3.543769] [<ffff0000085a4950>] driver_register+0x68/0x100
[ 3.549333] [<ffff0000085a5f44>] __platform_driver_register+0x54/0x60
[ 3.555767] [<ffff000008d8cecc>] rsnd_driver_init+0x18/0x20
[ 3.561331] [<ffff0000080839ac>] do_one_initcall+0x44/0x138
[ 3.566897] [<ffff000008d40d84>] kernel_init_freeable+0x1f8/0x298
[ 3.572983] [<ffff00000899a498>] kernel_init+0x18/0x108
[ 3.578200] [<ffff000008083710>] ret_from_fork+0x10/0x40
Thanks,
Ramesh
