[PATCH] i2c_powermac: shut up lockdep warning
Michael Ellerman
mpe at ellerman.id.au
Mon Oct 10 16:35:17 AEDT 2016
Denis Kirjanov <kda at linux-powerpc.org> writes:
> On 9/21/16, Denis Kirjanov <kda at linux-powerpc.org> 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: [<c000000000052830>]
>> .pmac_i2c_open+0x30/0x100
>> [ 20.507819]
>> [ 20.507819] but task is already holding lock:
>> [ 20.507829] (&policy->rwsem){+.+.+.}, at: [<c00000000068adcc>]
>> .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] [<c00000000082385c>] .down_write+0x6c/0x110
>> [ 20.507849] [<c00000000068adcc>] .cpufreq_online+0x1ac/0x9d0
>> [ 20.507855] [<c0000000004d76d8>]
>> .subsys_interface_register+0xb8/0x110
>> [ 20.507860] [<c000000000689bb0>]
>> .cpufreq_register_driver+0x1d0/0x250
>> [ 20.507866] [<c000000000b4f8f4>] .g5_cpufreq_init+0x9cc/0xa28
>> [ 20.507872] [<c00000000000a98c>] .do_one_initcall+0x5c/0x1d0
>> [ 20.507878] [<c000000000b0f86c>]
>> .kernel_init_freeable+0x1ac/0x28c
>> [ 20.507883] [<c00000000000b3bc>] .kernel_init+0x1c/0x140
>> [ 20.507887] [<c0000000000098f4>]
>> .ret_from_kernel_thread+0x58/0x64
>> [ 20.507894]
>> [ 20.507894] -> #3 (subsys mutex#2){+.+.+.}:
>> [ 20.507899] [<c000000000820448>] .mutex_lock_nested+0xa8/0x590
>> [ 20.507903] [<c0000000004d7f24>] .bus_probe_device+0x44/0xe0
>> [ 20.507907] [<c0000000004d5208>] .device_add+0x508/0x730
>> [ 20.507911] [<c0000000004dd528>] .register_cpu+0x118/0x190
>> [ 20.507916] [<c000000000b14450>] .topology_init+0x148/0x248
>> [ 20.507921] [<c00000000000a98c>] .do_one_initcall+0x5c/0x1d0
>> [ 20.507925] [<c000000000b0f86c>]
>> .kernel_init_freeable+0x1ac/0x28c
>> [ 20.507929] [<c00000000000b3bc>] .kernel_init+0x1c/0x140
>> [ 20.507934] [<c0000000000098f4>]
>> .ret_from_kernel_thread+0x58/0x64
>> [ 20.507939]
>> [ 20.507939] -> #2 (cpu_add_remove_lock){+.+.+.}:
>> [ 20.507944] [<c000000000820448>] .mutex_lock_nested+0xa8/0x590
>> [ 20.507950] [<c000000000087a9c>] .register_cpu_notifier+0x2c/0x70
>> [ 20.507955] [<c000000000b267e0>] .spawn_ksoftirqd+0x18/0x4c
>> [ 20.507959] [<c00000000000a98c>] .do_one_initcall+0x5c/0x1d0
>> [ 20.507964] [<c000000000b0f770>] .kernel_init_freeable+0xb0/0x28c
>> [ 20.507968] [<c00000000000b3bc>] .kernel_init+0x1c/0x140
>> [ 20.507972] [<c0000000000098f4>]
>> .ret_from_kernel_thread+0x58/0x64
>> [ 20.507978]
>> [ 20.507978] -> #1 (&host->mutex){+.+.+.}:
>> [ 20.507982] [<c000000000820448>] .mutex_lock_nested+0xa8/0x590
>> [ 20.507987] [<c0000000000527e8>] .kw_i2c_open+0x18/0x30
>> [ 20.507991] [<c000000000052894>] .pmac_i2c_open+0x94/0x100
>> [ 20.507995] [<c000000000b220a0>] .smp_core99_probe+0x260/0x410
>> [ 20.507999] [<c000000000b185bc>] .smp_prepare_cpus+0x280/0x2ac
>> [ 20.508003] [<c000000000b0f748>] .kernel_init_freeable+0x88/0x28c
>> [ 20.508008] [<c00000000000b3bc>] .kernel_init+0x1c/0x140
>> [ 20.508012] [<c0000000000098f4>]
>> .ret_from_kernel_thread+0x58/0x64
>> [ 20.508018]
>> [ 20.508018] -> #0 (&bus->mutex){+.+.+.}:
>> [ 20.508023] [<c0000000000ed5b4>] .lock_acquire+0x84/0x100
>> [ 20.508027] [<c000000000820448>] .mutex_lock_nested+0xa8/0x590
>> [ 20.508032] [<c000000000052830>] .pmac_i2c_open+0x30/0x100
>> [ 20.508037] [<c000000000052e14>] .pmac_i2c_do_begin+0x34/0x120
>> [ 20.508040] [<c000000000056bc0>] .pmf_call_one+0x50/0xd0
>> [ 20.508045] [<c00000000068ff1c>] .g5_pfunc_switch_volt+0x2c/0xc0
>> [ 20.508050] [<c00000000068fecc>]
>> .g5_pfunc_switch_freq+0x1cc/0x1f0
>> [ 20.508054] [<c00000000068fc2c>] .g5_cpufreq_target+0x2c/0x40
>> [ 20.508058] [<c0000000006873ec>]
>> .__cpufreq_driver_target+0x23c/0x840
>> [ 20.508062] [<c00000000068c798>]
>> .cpufreq_gov_performance_limits+0x18/0x30
>> [ 20.508067] [<c00000000068915c>]
>> .cpufreq_start_governor+0xac/0x100
>> [ 20.508071] [<c00000000068a788>] .cpufreq_set_policy+0x208/0x260
>> [ 20.508076] [<c00000000068abdc>] .cpufreq_init_policy+0x6c/0xb0
>> [ 20.508081] [<c00000000068ae70>] .cpufreq_online+0x250/0x9d0
>> [ 20.508085] [<c0000000004d76d8>]
>> .subsys_interface_register+0xb8/0x110
>> [ 20.508090] [<c000000000689bb0>]
>> .cpufreq_register_driver+0x1d0/0x250
>> [ 20.508094] [<c000000000b4f8f4>] .g5_cpufreq_init+0x9cc/0xa28
>> [ 20.508099] [<c00000000000a98c>] .do_one_initcall+0x5c/0x1d0
>> [ 20.508103] [<c000000000b0f86c>]
>> .kernel_init_freeable+0x1ac/0x28c
>> [ 20.508107] [<c00000000000b3bc>] .kernel_init+0x1c/0x140
>> [ 20.508112] [<c0000000000098f4>]
>> .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: [<c000000000087838>]
>> .get_online_cpus+0x48/0xc0
>> [ 20.508159] #1: (subsys mutex#2){+.+.+.}, at: [<c0000000004d7670>]
>> .subsys_interface_register+0x50/0x110
>> [ 20.508168] #2: (&policy->rwsem){+.+.+.}, at: [<c00000000068adcc>]
>> .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 <kda at linux-powerpc.org>
>> ---
>
> Hi Michael,
>
> are you going to take this patch? The issue appears to me for a long time
I guess. Ben's response was a bit equivocal. But I guess he meant "seems
OK". So yeah I'll pick it up for 4.10.
cheers
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