From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3tHTzf3DwvzDvNT for ; Mon, 14 Nov 2016 23:17:18 +1100 (AEDT) In-Reply-To: <1474457698-3855-1-git-send-email-kda@linux-powerpc.org> To: Denis Kirjanov , linuxppc-dev@lists.ozlabs.org From: Michael Ellerman Cc: Denis Kirjanov Subject: Re: i2c_powermac: shut up lockdep warning Message-Id: <3tHTzf1fxFz9s5w@ozlabs.org> Date: Mon, 14 Nov 2016 23:17:17 +1100 (AEDT) List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 2016-21-09 at 11:34:58 UTC, Denis Kirjanov wrote: > That's unclear why lockdep shows the following warning but adding a > lockdep class to struct pmac_i2c_bus solves it > > [ 20.507795] ====================================================== > [ 20.507796] [ INFO: possible circular locking dependency detected ] > [ 20.507800] 4.8.0-rc7-00037-gd2ffb01 #21 Not tainted > [ 20.507801] ------------------------------------------------------- > [ 20.507803] swapper/0/1 is trying to acquire lock: > [ 20.507818] (&bus->mutex){+.+.+.}, at: [] .pmac_i2c_open+0x30/0x100 > [ 20.507819] > [ 20.507819] but task is already holding lock: > [ 20.507829] (&policy->rwsem){+.+.+.}, at: [] .cpufreq_online+0x1ac/0x9d0 > [ 20.507830] > [ 20.507830] which lock already depends on the new lock. > [ 20.507830] > [ 20.507832] > [ 20.507832] the existing dependency chain (in reverse order) is: > [ 20.507837] > [ 20.507837] -> #4 (&policy->rwsem){+.+.+.}: > [ 20.507844] [] .down_write+0x6c/0x110 > [ 20.507849] [] .cpufreq_online+0x1ac/0x9d0 > [ 20.507855] [] .subsys_interface_register+0xb8/0x110 > [ 20.507860] [] .cpufreq_register_driver+0x1d0/0x250 > [ 20.507866] [] .g5_cpufreq_init+0x9cc/0xa28 > [ 20.507872] [] .do_one_initcall+0x5c/0x1d0 > [ 20.507878] [] .kernel_init_freeable+0x1ac/0x28c > [ 20.507883] [] .kernel_init+0x1c/0x140 > [ 20.507887] [] .ret_from_kernel_thread+0x58/0x64 > [ 20.507894] > [ 20.507894] -> #3 (subsys mutex#2){+.+.+.}: > [ 20.507899] [] .mutex_lock_nested+0xa8/0x590 > [ 20.507903] [] .bus_probe_device+0x44/0xe0 > [ 20.507907] [] .device_add+0x508/0x730 > [ 20.507911] [] .register_cpu+0x118/0x190 > [ 20.507916] [] .topology_init+0x148/0x248 > [ 20.507921] [] .do_one_initcall+0x5c/0x1d0 > [ 20.507925] [] .kernel_init_freeable+0x1ac/0x28c > [ 20.507929] [] .kernel_init+0x1c/0x140 > [ 20.507934] [] .ret_from_kernel_thread+0x58/0x64 > [ 20.507939] > [ 20.507939] -> #2 (cpu_add_remove_lock){+.+.+.}: > [ 20.507944] [] .mutex_lock_nested+0xa8/0x590 > [ 20.507950] [] .register_cpu_notifier+0x2c/0x70 > [ 20.507955] [] .spawn_ksoftirqd+0x18/0x4c > [ 20.507959] [] .do_one_initcall+0x5c/0x1d0 > [ 20.507964] [] .kernel_init_freeable+0xb0/0x28c > [ 20.507968] [] .kernel_init+0x1c/0x140 > [ 20.507972] [] .ret_from_kernel_thread+0x58/0x64 > [ 20.507978] > [ 20.507978] -> #1 (&host->mutex){+.+.+.}: > [ 20.507982] [] .mutex_lock_nested+0xa8/0x590 > [ 20.507987] [] .kw_i2c_open+0x18/0x30 > [ 20.507991] [] .pmac_i2c_open+0x94/0x100 > [ 20.507995] [] .smp_core99_probe+0x260/0x410 > [ 20.507999] [] .smp_prepare_cpus+0x280/0x2ac > [ 20.508003] [] .kernel_init_freeable+0x88/0x28c > [ 20.508008] [] .kernel_init+0x1c/0x140 > [ 20.508012] [] .ret_from_kernel_thread+0x58/0x64 > [ 20.508018] > [ 20.508018] -> #0 (&bus->mutex){+.+.+.}: > [ 20.508023] [] .lock_acquire+0x84/0x100 > [ 20.508027] [] .mutex_lock_nested+0xa8/0x590 > [ 20.508032] [] .pmac_i2c_open+0x30/0x100 > [ 20.508037] [] .pmac_i2c_do_begin+0x34/0x120 > [ 20.508040] [] .pmf_call_one+0x50/0xd0 > [ 20.508045] [] .g5_pfunc_switch_volt+0x2c/0xc0 > [ 20.508050] [] .g5_pfunc_switch_freq+0x1cc/0x1f0 > [ 20.508054] [] .g5_cpufreq_target+0x2c/0x40 > [ 20.508058] [] .__cpufreq_driver_target+0x23c/0x840 > [ 20.508062] [] .cpufreq_gov_performance_limits+0x18/0x30 > [ 20.508067] [] .cpufreq_start_governor+0xac/0x100 > [ 20.508071] [] .cpufreq_set_policy+0x208/0x260 > [ 20.508076] [] .cpufreq_init_policy+0x6c/0xb0 > [ 20.508081] [] .cpufreq_online+0x250/0x9d0 > [ 20.508085] [] .subsys_interface_register+0xb8/0x110 > [ 20.508090] [] .cpufreq_register_driver+0x1d0/0x250 > [ 20.508094] [] .g5_cpufreq_init+0x9cc/0xa28 > [ 20.508099] [] .do_one_initcall+0x5c/0x1d0 > [ 20.508103] [] .kernel_init_freeable+0x1ac/0x28c > [ 20.508107] [] .kernel_init+0x1c/0x140 > [ 20.508112] [] .ret_from_kernel_thread+0x58/0x64 > [ 20.508113] > [ 20.508113] other info that might help us debug this: > [ 20.508113] > [ 20.508121] Chain exists of: > [ 20.508121] &bus->mutex --> subsys mutex#2 --> &policy->rwsem > [ 20.508121] > [ 20.508123] Possible unsafe locking scenario: > [ 20.508123] > [ 20.508124] CPU0 CPU1 > [ 20.508125] ---- ---- > [ 20.508128] lock(&policy->rwsem); > [ 20.508132] lock(subsys mutex#2); > [ 20.508135] lock(&policy->rwsem); > [ 20.508138] lock(&bus->mutex); > [ 20.508139] > [ 20.508139] *** DEADLOCK *** > [ 20.508139] > [ 20.508141] 3 locks held by swapper/0/1: > [ 20.508150] #0: (cpu_hotplug.lock){++++++}, at: [] .get_online_cpus+0x48/0xc0 > [ 20.508159] #1: (subsys mutex#2){+.+.+.}, at: [] .subsys_interface_register+0x50/0x110 > [ 20.508168] #2: (&policy->rwsem){+.+.+.}, at: [] .cpufreq_online+0x1ac/0x9d0 > [ 20.508169] > [ 20.508169] stack backtrace: > [ 20.508173] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.8.0-rc7-00037-gd2ffb01 #21 > [ 20.508175] Call Trace: > [ 20.508180] [c0000000790c2b90] [c00000000082cc70] .dump_stack+0xe0/0x14c (unreliable) > [ 20.508184] [c0000000790c2c20] [c000000000828c88] .print_circular_bug+0x350/0x388 > [ 20.508188] [c0000000790c2cd0] [c0000000000ecb0c] .__lock_acquire+0x196c/0x1d30 > [ 20.508192] [c0000000790c2e50] [c0000000000ed5b4] .lock_acquire+0x84/0x100 > [ 20.508196] [c0000000790c2f20] [c000000000820448] .mutex_lock_nested+0xa8/0x590 > [ 20.508201] [c0000000790c3030] [c000000000052830] .pmac_i2c_open+0x30/0x100 > [ 20.508206] [c0000000790c30c0] [c000000000052e14] .pmac_i2c_do_begin+0x34/0x120 > [ 20.508209] [c0000000790c3150] [c000000000056bc0] .pmf_call_one+0x50/0xd0 > [ 20.508213] [c0000000790c31e0] [c00000000068ff1c] .g5_pfunc_switch_volt+0x2c/0xc0 > [ 20.508217] [c0000000790c3250] [c00000000068fecc] .g5_pfunc_switch_freq+0x1cc/0x1f0 > [ 20.508221] [c0000000790c3320] [c00000000068fc2c] .g5_cpufreq_target+0x2c/0x40 > [ 20.508226] [c0000000790c3390] [c0000000006873ec] .__cpufreq_driver_target+0x23c/0x840 > [ 20.508230] [c0000000790c3440] [c00000000068c798] .cpufreq_gov_performance_limits+0x18/0x30 > [ 20.508235] [c0000000790c34b0] [c00000000068915c] .cpufreq_start_governor+0xac/0x100 > [ 20.508239] [c0000000790c3530] [c00000000068a788] .cpufreq_set_policy+0x208/0x260 > [ 20.508244] [c0000000790c35d0] [c00000000068abdc] .cpufreq_init_policy+0x6c/0xb0 > [ 20.508249] [c0000000790c3940] [c00000000068ae70] .cpufreq_online+0x250/0x9d0 > [ 20.508253] [c0000000790c3a30] [c0000000004d76d8] .subsys_interface_register+0xb8/0x110 > [ 20.508258] [c0000000790c3ad0] [c000000000689bb0] .cpufreq_register_driver+0x1d0/0x250 > [ 20.508262] [c0000000790c3b60] [c000000000b4f8f4] .g5_cpufreq_init+0x9cc/0xa28 > [ 20.508267] [c0000000790c3c20] [c00000000000a98c] .do_one_initcall+0x5c/0x1d0 > [ 20.508271] [c0000000790c3d00] [c000000000b0f86c] .kernel_init_freeable+0x1ac/0x28c > [ 20.508276] [c0000000790c3db0] [c00000000000b3bc] .kernel_init+0x1c/0x140 > [ 20.508280] [c0000000790c3e30] [c0000000000098f4] .ret_from_kernel_thread+0x58/0x64 > > Signed-off-by: Denis Kirjanov Applied to powerpc next, thanks. https://git.kernel.org/powerpc/c/9e607f72748ddc5620aeeb8d1f32f3 cheers