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Message-ID: <e60c6055ad3902031e3bb632b7503ff68a9c215d.camel@siemens.com>
Date:   Mon, 15 May 2023 12:04:10 +0000
From:   "Sverdlin, Alexander" <alexander.sverdlin@...mens.com>
To:     "alexander.stein@...tq-group.com" <alexander.stein@...tq-group.com>
CC:     "linux-imx@....com" <linux-imx@....com>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "aisheng.dong@....com" <aisheng.dong@....com>
Subject: Re: [PATCH v3] i2c: lpi2c: cache peripheral clock rate

Hello Alexander!

On Mon, 2023-05-15 at 11:11 +0200, Alexander Stein wrote:
> > [   22.503179] other info that might help us debug this:
> > [   22.503179]
> > [   22.503183] Chain exists of:
> > [   22.503183]   prepare_lock --> rtc_pcf85063:594:(&config-
> > >regmap)->lock
> > --> i2c_register_adapter
> > [   22.503183]
> > [   22.503207]  Possible unsafe locking scenario:
> > [   22.503207]
> > [   22.503210]        CPU0                    CPU1
> > [   22.503213]        ----                    ----
> > [   22.503216]   lock(i2c_register_adapter);
> > [   22.503225]                               
> > lock(rtc_pcf85063:594:(&config-
> > > regmap)->lock);
> > 
> > [   22.503235]                               
> > lock(i2c_register_adapter);
> > [   22.503244]   lock(prepare_lock);
> > [   22.503253]
> > [   22.503253]  *** DEADLOCK ***
> > 
> > Now lpi2c_runtime_resume will call into clk_prepare() which also
> > calls
> > clk_prepare_lock() (identical to clk_get_rate).
> > 
> > Best regards,
> > Alexader
> > 
> > >         pm_runtime_set_autosuspend_delay(&pdev->dev,
> > > I2C_PM_TIMEOUT);
> > >         pm_runtime_use_autosuspend(&pdev->dev);
> > >         pm_runtime_get_noresume(&pdev->dev);
> 
> With commit fa39065833db ("i2c: imx-lpi2c: avoid taking clk_prepare
> mutex in 
> PM callbacks") in place, the additional deadlock warning regarding
> runtime 
> resume is gone.
> So only the ordering issue needs to be addressed.

Unfortunately with both your (backported) and my patches applied I've
got a 3rd warning:

======================================================
WARNING: possible circular locking dependency detected
5.15.71+git8e43aee #1 Tainted: G           O     
------------------------------------------------------
xxxxxxx/2238 is trying to acquire lock:
ffff0000040bda40 (&desc->request_mutex){+.+.}-{3:3}, at:
__setup_irq+0xbc/0x8bc

but task is already holding lock:
ffff000010ef1100 (i2c_register_adapter){+.+.}-{3:3}, at:
i2c_adapter_lock_bus+0x2c/0x3c

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #5 (i2c_register_adapter){+.+.}-{3:3}:
       lock_acquire+0x68/0x84
       rt_mutex_lock_nested+0x88/0xe0
       i2c_adapter_lock_bus+0x2c/0x3c
       i2c_transfer+0x58/0x130
       regmap_i2c_read+0x64/0xb0
       _regmap_raw_read+0x114/0x440
       _regmap_bus_read+0x4c/0x84
       _regmap_read+0x6c/0x270
       regmap_read+0x54/0x80
       pcf85063_probe+0xec/0x4cc
       i2c_device_probe+0x10c/0x350
       really_probe+0xc4/0x470
       __driver_probe_device+0x11c/0x190
       driver_probe_device+0x48/0x110
       __device_attach_driver+0xc4/0x160
       bus_for_each_drv+0x80/0xe0
       __device_attach+0xb0/0x1f0
       device_initial_probe+0x1c/0x2c
       bus_probe_device+0xa4/0xb0
       device_add+0x398/0x8ac
       device_register+0x28/0x40
       i2c_new_client_device+0x144/0x290
       of_i2c_register_devices+0x18c/0x230
       i2c_register_adapter+0x1dc/0x6b0
       __i2c_add_numbered_adapter+0x68/0xbc
       i2c_add_adapter+0xb0/0xe0
       lpi2c_imx_probe+0x3a4/0x670
       platform_probe+0x70/0xec
       really_probe+0xc4/0x470
       __driver_probe_device+0x11c/0x190
       driver_probe_device+0x48/0x110
       __device_attach_driver+0xc4/0x160
       bus_for_each_drv+0x80/0xe0
       __device_attach+0xb0/0x1f0
       device_initial_probe+0x1c/0x2c
       bus_probe_device+0xa4/0xb0
       deferred_probe_work_func+0xb8/0x110
       process_one_work+0x27c/0x6c4
       worker_thread+0x7c/0x450
       kthread+0x168/0x17c
       ret_from_fork+0x10/0x20

-> #4 (rtc_pcf85063:560:(&config->regmap)->lock){+.+.}-{3:3}:
       lock_acquire+0x68/0x84
       __mutex_lock+0xa8/0x4d0
       mutex_lock_nested+0x48/0x54
       regmap_lock_mutex+0x1c/0x30
       regmap_read+0x44/0x80
       pcf85063_clkout_recalc_rate+0x34/0x80
       __clk_register+0x520/0x880
       devm_clk_register+0x64/0xc4
       pcf85063_probe+0x24c/0x4cc
       i2c_device_probe+0x10c/0x350
       really_probe+0xc4/0x470
       __driver_probe_device+0x11c/0x190
       driver_probe_device+0x48/0x110
       __device_attach_driver+0xc4/0x160
       bus_for_each_drv+0x80/0xe0
       __device_attach+0xb0/0x1f0
       device_initial_probe+0x1c/0x2c
       bus_probe_device+0xa4/0xb0
       device_add+0x398/0x8ac
       device_register+0x28/0x40
       i2c_new_client_device+0x144/0x290
       of_i2c_register_devices+0x18c/0x230
       i2c_register_adapter+0x1dc/0x6b0
       __i2c_add_numbered_adapter+0x68/0xbc
       i2c_add_adapter+0xb0/0xe0
       lpi2c_imx_probe+0x3a4/0x670
       platform_probe+0x70/0xec
       really_probe+0xc4/0x470
       __driver_probe_device+0x11c/0x190
       driver_probe_device+0x48/0x110
       __device_attach_driver+0xc4/0x160
       bus_for_each_drv+0x80/0xe0
       __device_attach+0xb0/0x1f0
       device_initial_probe+0x1c/0x2c
       bus_probe_device+0xa4/0xb0
       deferred_probe_work_func+0xb8/0x110
       process_one_work+0x27c/0x6c4
       worker_thread+0x7c/0x450
       kthread+0x168/0x17c
       ret_from_fork+0x10/0x20

-> #3 (prepare_lock){+.+.}-{3:3}:
       lock_acquire+0x68/0x84
       __mutex_lock+0xa8/0x4d0
       mutex_lock_nested+0x48/0x54
       clk_prepare_lock+0x50/0xb0
       clk_prepare+0x28/0x50
       fec_runtime_resume+0x3c/0xe0
       pm_generic_runtime_resume+0x34/0x50
       __genpd_runtime_resume+0x38/0x90
       genpd_runtime_resume+0xa0/0x304
       __rpm_callback+0x50/0x1b0
       rpm_callback+0x40/0x80
       rpm_resume+0x448/0x6e0
       __pm_runtime_resume+0x50/0xc0
       fec_enet_mdio_read+0x48/0x190
       __mdiobus_read+0x48/0xb0
       mdiobus_read_nested+0x48/0x70
       mv88e6xxx_smi_dual_direct_read+0x2c/0x50
       mv88e6xxx_read+0x64/0xf0
       mv88e6xxx_g1_read+0x28/0x34
       mv88e6xxx_g1_irq_thread_work+0x50/0x17c
       mv88e6xxx_irq_poll+0x28/0x50
       kthread_worker_fn+0x100/0x480
       kthread+0x168/0x17c
       ret_from_fork+0x10/0x20

-> #2 (&bus->mdio_lock/2){+.+.}-{3:3}:
       lock_acquire+0x68/0x84
       __mutex_lock+0xa8/0x4d0
       mutex_lock_nested+0x48/0x54
       mdiobus_read_nested+0x38/0x70
       mv88e6xxx_smi_dual_direct_read+0x2c/0x50
       mv88e6xxx_read+0x64/0xf0
       mv88e6xxx_port_read+0x24/0x30
       mv88e6xxx_probe+0x250/0x7f0
       mdio_probe+0x3c/0x80
       really_probe+0xc4/0x470
       __driver_probe_device+0x11c/0x190
       driver_probe_device+0x48/0x110
       __device_attach_driver+0xc4/0x160
       bus_for_each_drv+0x80/0xe0
       __device_attach+0xb0/0x1f0
       device_initial_probe+0x1c/0x2c
       bus_probe_device+0xa4/0xb0
       deferred_probe_work_func+0xb8/0x110
       process_one_work+0x27c/0x6c4
       worker_thread+0x7c/0x450
       kthread+0x168/0x17c
       ret_from_fork+0x10/0x20

-> #1 (&chip->reg_lock){+.+.}-{3:3}:
       lock_acquire+0x68/0x84
       __mutex_lock+0xa8/0x4d0
       mutex_lock_nested+0x48/0x54
       mv88e6xxx_g1_irq_bus_lock+0x24/0x30
       __setup_irq+0x6e0/0x8bc
       request_threaded_irq+0xf4/0x1b4
       mv88e6xxx_g2_irq_setup+0x1f0/0x2b4
       mv88e6xxx_probe+0x480/0x7f0
       mdio_probe+0x3c/0x80
       really_probe+0xc4/0x470
       __driver_probe_device+0x11c/0x190
       driver_probe_device+0x48/0x110
       __device_attach_driver+0xc4/0x160
       bus_for_each_drv+0x80/0xe0
       __device_attach+0xb0/0x1f0
       device_initial_probe+0x1c/0x2c
       bus_probe_device+0xa4/0xb0
       deferred_probe_work_func+0xb8/0x110
       process_one_work+0x27c/0x6c4
       worker_thread+0x7c/0x450
       kthread+0x168/0x17c
       ret_from_fork+0x10/0x20

-> #0 (&desc->request_mutex){+.+.}-{3:3}:
       __lock_acquire+0x12a4/0x20a0
       lock_acquire.part.0+0xe0/0x230
       lock_acquire+0x68/0x84
       __mutex_lock+0xa8/0x4d0
       mutex_lock_nested+0x48/0x54
       __setup_irq+0xbc/0x8bc
       request_threaded_irq+0xf4/0x1b4
       devm_request_threaded_irq+0x88/0x104
       lpi2c_runtime_resume+0x70/0xe4
       pm_generic_runtime_resume+0x34/0x50
       __genpd_runtime_resume+0x38/0x90
       genpd_runtime_resume+0xa0/0x304
       __rpm_callback+0x50/0x1b0
       rpm_callback+0x74/0x80
       rpm_resume+0x448/0x6e0
       __pm_runtime_resume+0x50/0xc0
       lpi2c_imx_xfer+0x60/0xa5c
       __i2c_transfer+0x174/0xa80
       i2c_transfer+0x68/0x130
       regmap_i2c_read+0x64/0xb0
       _regmap_raw_read+0x114/0x440
       regmap_raw_read+0x19c/0x28c
       regmap_bulk_read+0x1b8/0x244
       at24_read+0x14c/0x2c4
       nvmem_reg_read+0x2c/0x54
       bin_attr_nvmem_read+0x8c/0xbc
       sysfs_kf_bin_read+0x74/0x94
       kernfs_fop_read_iter+0xb0/0x1d0
       new_sync_read+0xf0/0x184
       vfs_read+0x154/0x1f0
       ksys_read+0x70/0x100
       __arm64_sys_read+0x24/0x30
       invoke_syscall+0x50/0x120
       el0_svc_common.constprop.0+0x68/0x124
       do_el0_svc+0x30/0x9c
       el0_svc+0x54/0x110
       el0t_64_sync_handler+0xa4/0x130
       el0t_64_sync+0x1a0/0x1a4

other info that might help us debug this:

Chain exists of:
  &desc->request_mutex --> rtc_pcf85063:560:(&config->regmap)->lock -->
i2c_register_adapter

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(i2c_register_adapter);
                               lock(rtc_pcf85063:560:(&config->regmap)-
>lock);
                               lock(i2c_register_adapter);
  lock(&desc->request_mutex);

 *** DEADLOCK ***

4 locks held by xxxxxxx/2238:
 #0: ffff000015a64488 (&of->mutex){+.+.}-{3:3}, at:
kernfs_fop_read_iter+0x74/0x1d0
 #1: ffff0000119e2400 (kn->active#58){.+.+}-{0:0}, at:
kernfs_fop_read_iter+0x7c/0x1d0
 #2: ffff0000119a26e8 (&at24->lock){+.+.}-{3:3}, at:
at24_read+0x8c/0x2c4
 #3: ffff000010ef1100 (i2c_register_adapter){+.+.}-{3:3}, at:
i2c_adapter_lock_bus+0x2c/0x3c

stack backtrace:
CPU: 1 PID: 2238 Comm: xxxxxxx Tainted: G           O     
5.15.71+git8e43aee #1
Hardware name: Siemens PXC5.E24 (DT)
Call trace:
 dump_backtrace+0x0/0x1d4
 show_stack+0x20/0x2c
 dump_stack_lvl+0x8c/0xb8
 dump_stack+0x18/0x34
 print_circular_bug+0x1f8/0x200
 check_noncircular+0x130/0x144
 __lock_acquire+0x12a4/0x20a0
 lock_acquire.part.0+0xe0/0x230
 lock_acquire+0x68/0x84
 __mutex_lock+0xa8/0x4d0
 mutex_lock_nested+0x48/0x54
 __setup_irq+0xbc/0x8bc
 request_threaded_irq+0xf4/0x1b4
 devm_request_threaded_irq+0x88/0x104
 lpi2c_runtime_resume+0x70/0xe4
 pm_generic_runtime_resume+0x34/0x50
 __genpd_runtime_resume+0x38/0x90
 genpd_runtime_resume+0xa0/0x304
 __rpm_callback+0x50/0x1b0
 rpm_callback+0x74/0x80
 rpm_resume+0x448/0x6e0
 __pm_runtime_resume+0x50/0xc0
 lpi2c_imx_xfer+0x60/0xa5c
 __i2c_transfer+0x174/0xa80
 i2c_transfer+0x68/0x130
 regmap_i2c_read+0x64/0xb0
 _regmap_raw_read+0x114/0x440
 regmap_raw_read+0x19c/0x28c
 regmap_bulk_read+0x1b8/0x244
 at24_read+0x14c/0x2c4
 nvmem_reg_read+0x2c/0x54
 bin_attr_nvmem_read+0x8c/0xbc
 sysfs_kf_bin_read+0x74/0x94
 kernfs_fop_read_iter+0xb0/0x1d0
 new_sync_read+0xf0/0x184
 vfs_read+0x154/0x1f0
 ksys_read+0x70/0x100
 __arm64_sys_read+0x24/0x30
 invoke_syscall+0x50/0x120
 el0_svc_common.constprop.0+0x68/0x124
 do_el0_svc+0x30/0x9c
 el0_svc+0x54/0x110
 el0t_64_sync_handler+0xa4/0x130
 el0t_64_sync+0x1a0/0x1a4

So this doesn't look like an end of the story yet, unfortunately.

-- 
Alexander Sverdlin
Siemens AG
www.siemens.com

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