On Wednesday, September 21, 2016, Denis Kirjanov <k...@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
HI Ben,
could you give any comments on this?
Thanks!
>
> [ 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 <k...@linux-powerpc.org <javascript:;>>
> ---
> arch/powerpc/platforms/powermac/low_i2c.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/arch/powerpc/platforms/powermac/low_i2c.c
> b/arch/powerpc/platforms/powermac/low_i2c.c
> index 6d6f277..0159363 100644
> --- a/arch/powerpc/platforms/powermac/low_i2c.c
> +++ b/arch/powerpc/platforms/powermac/low_i2c.c
> @@ -90,6 +90,7 @@ struct pmac_i2c_bus
> int opened;
> int polled; /* open mode */
> struct platform_device *platform_dev;
> + struct lock_class_key lock_key;
>
> /* ops */
> int (*open)(struct pmac_i2c_bus *bus);
> @@ -587,6 +588,7 @@ static void __init kw_i2c_add(struct pmac_i2c_host_kw
> *host,
> bus->close = kw_i2c_close;
> bus->xfer = kw_i2c_xfer;
> mutex_init(&bus->mutex);
> + lockdep_set_class(&bus->mutex, &bus->lock_key);
> if (controller == busnode)
> bus->flags = pmac_i2c_multibus;
> list_add(&bus->link, &pmac_i2c_busses);
> @@ -815,6 +817,7 @@ static void __init pmu_i2c_probe(void)
> bus->hostdata = bus + 1;
> bus->xfer = pmu_i2c_xfer;
> mutex_init(&bus->mutex);
> + lockdep_set_class(&bus->mutex, &bus->lock_key);
> bus->flags = pmac_i2c_multibus;
> list_add(&bus->link, &pmac_i2c_busses);
>
> @@ -938,6 +941,7 @@ static void __init smu_i2c_probe(void)
> bus->hostdata = bus + 1;
> bus->xfer = smu_i2c_xfer;
> mutex_init(&bus->mutex);
> + lockdep_set_class(&bus->mutex, &bus->lock_key);
> bus->flags = 0;
> list_add(&bus->link, &pmac_i2c_busses);
>
> --
> 2.4.0
>
>
