On 2023/02/07 0:45, Alan Stern wrote:
> On Mon, Feb 06, 2023 at 11:13:38PM +0900, Tetsuo Handa wrote:
>> On 2023/02/05 10:23, Alan Stern wrote:
>>> I suppose we could create separate lockdep classes for every bus_type
>>> and device_type combination, as well as for the different sorts of
>>> devices -- treat things like class devices separately from normal
>>> devices, and so on. But even then there would be trouble.
>>
>> Sorry, since I'm not familiar with devices, I can't interpret what you
>> are talking about in this response. But why don't you try test5() approach
>> in an example module shown below (i.e. treat all dev->mutex instances
>> independent to each other) ?
>>
>> Sharing mutex_init() (like test2() approach) causes false positives,
>> but allocating a key on each dev->mutex (like test5() approach) should
>> avoid false positives.
>
> Interesting idea. I'm doubtful that it will accomplish all that you
> want. After all, one of lockdep's biggest advantages is that it can
> detect the potential for deadlocks without a deadlock actually
> occurring. By putting each mutex into its own class, you lose much of
> this ability.
>
> But who knows? Maybe it will be a big help.
>
> Anyway, below is a patch you can try, based on the code for your test5.
> Let me know what happens.
>
It boots, except lockdep_register_key() hit WARN_ON_ONCE() at
device_register(&platform_bus) from platform_bus_init(), for
platform_bus is a static object.
struct device platform_bus = {
.init_name = "platform",
};
We need to skip lockdep_register_key()/lockdep_unregister_key() on
static "struct device" instances...
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[ 0.550046][ T1] smpboot: Total of 12 processors activated (74513.31 BogoMIPS)
[ 0.559082][ T1] devtmpfs: initialized
[ 0.560054][ T1] ------------[ cut here ]------------
[ 0.562046][ T1] WARNING: CPU: 0 PID: 1 at kernel/locking/lockdep.c:1223 lockdep_register_key+0x1a2/0x230
[ 0.564046][ T1] Modules linked in:
[ 0.565050][ T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.2.0-rc7+ #16
[ 0.567046][ T1] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020
[ 0.569077][ T1] RIP: 0010:lockdep_register_key+0x1a2/0x230
[ 0.571046][ T1] Code: 89 03 4a 89 1c e5 60 b1 e8 84 48 85 c0 0f 84 27 ff ff ff 8b 3d c7 68 f8 01 48 89 58 08 85 ff 0f 85 54 ff ff ff e9 1a ff ff ff <0f> 0b 5b 41 5c 41 5d 41 5e 5d c3 89 c6 48 c7 c7 70 41 05 85 e8 35
[ 0.573046][ T1] RSP: 0000:ffffadbb00017e80 EFLAGS: 00010202
[ 0.575046][ T1] RAX: 0000000000000001 RBX: ffffffff8443f5d0 RCX: 0000000000000000
[ 0.577054][ T1] RDX: 0000000000000001 RSI: 0000000000000001 RDI: ffffffff8443f5d0
[ 0.579069][ T1] RBP: ffffadbb00017ea0 R08: 0000000000000003 R09: 0000000000000000
[ 0.581069][ T1] R10: d6bf87c490213bdc R11: 0000000000000001 R12: ffffffff8443f5d0
[ 0.583069][ T1] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
[ 0.585058][ T1] FS: 0000000000000000(0000) GS:ffff9b7ef6e00000(0000) knlGS:0000000000000000
[ 0.587046][ T1] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 0.589046][ T1] CR2: ffff9b7df0202000 CR3: 000000012f011001 CR4: 0000000000370ef0
[ 0.591046][ T1] Call Trace:
[ 0.592310][ T1] <TASK>
[ 0.594046][ T1] device_initialize+0x5f/0x170
[ 0.595046][ T1] device_register+0xd/0x20
[ 0.597046][ T1] platform_bus_init+0x16/0x4d
[ 0.598061][ T1] driver_init+0x2e/0x3a
[ 0.600054][ T1] kernel_init_freeable+0xc3/0x1d2
[ 0.601051][ T1] ? rest_init+0x190/0x190
[ 0.603051][ T1] kernel_init+0x15/0x120
[ 0.604273][ T1] ret_from_fork+0x1f/0x30
[ 0.606058][ T1] </TASK>
[ 0.607069][ T1] irq event stamp: 38345
[ 0.608284][ T1] hardirqs last enabled at (38357): [<ffffffff830d9953>] __up_console_sem+0x53/0x60
[ 0.610046][ T1] hardirqs last disabled at (38370): [<ffffffff830d9938>] __up_console_sem+0x38/0x60
[ 0.613054][ T1] softirqs last enabled at (38314): [<ffffffff838d54db>] __do_softirq+0x30b/0x46f
[ 0.615061][ T1] softirqs last disabled at (38309): [<ffffffff8306e859>] irq_exit_rcu+0xb9/0xf0
[ 0.617059][ T1] ---[ end trace 0000000000000000 ]---
[ 0.622102][ T1] ACPI: PM: Registering ACPI NVS region [mem 0xbfeff000-0xbfefffff] (4096 bytes)
[ 0.625130][ T1] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 1911260446275000 ns
----------
