[PATCH] [RFC] soc: imx: imx8m-blk-ctrl: Split clock prepare from clock enable in the domain
Marek Vasut
marex at denx.de
Tue Nov 8 16:28:03 PST 2022
On 10/25/22 02:25, Laurent Pinchart wrote:
> Hi Marek,
Hi,
> Thank you for the patch.
>
> On Mon, Oct 24, 2022 at 05:09:47PM +0200, Marek Vasut wrote:
>> It is possible for clk_disable_unused() to trigger lockdep warning
>> regarding lock ordering in this driver. This happens in case of the
>> following conditions:
>>
>> A) clock core clk_disable_unused() triggers the following sequence in a
>> driver which also uses blkctrl domain:
>> - clk_prepare_lock() -> obtains clock core prepare_lock
>> - pm_runtime_get*() -> obtains &blk_ctrl_genpd_lock_class
>>
>> B) driver powers up a power domain and triggers the following sequence
>> in blkctrl:
>> - pm_runtime_get_sync() -> obtains &blk_ctrl_genpd_lock_class
>> - clk_bulk_prepare_enable() -> obtains clock core prepare_lock
>>
>> This can lead to a deadlock in case A and B runs on separate CPUs.
>>
>> To avoid the deadlock, split clk_*prepare() from clk_*enable() and
>> call the former before pm_runtime_get_sync(). This way, the blkctrl
>> driver always claims the prepare_lock before blk_ctrl_genpd_lock_class
>> and the deadlock is avoided.
>
> I'm afraid I'm still getting occasional warnings from lockdep :-( This
> one happened at boot time:
>
> [ 17.837243]
> [ 17.837254] ======================================================
> [ 17.837256] WARNING: possible circular locking dependency detected
> [ 17.837260] 6.1.0-rc2-00199-gd504fb27855a-dirty #301 Not tainted
> [ 17.837265] ------------------------------------------------------
> [ 17.837267] kworker/u8:6/152 is trying to acquire lock:
> [ 17.837273] ffff000000eab6f0 (&blk_ctrl_genpd_lock_class){+.+.}-{3:3}, at: genpd_lock_mtx+0x20/0x30
> [ 17.837300]
> [ 17.837300] but task is already holding lock:
> [ 17.837302] ffff800009c1e5e8 (prepare_lock){+.+.}-{3:3}, at: clk_prepare_lock+0x34/0xb0
> [ 17.837321]
> [ 17.837321] which lock already depends on the new lock.
> [ 17.837321]
> [ 17.837323]
> [ 17.837323] the existing dependency chain (in reverse order) is:
> [ 17.837326]
> [ 17.837326] -> #1 (prepare_lock){+.+.}-{3:3}:
> [ 17.837337] lock_acquire+0x68/0x90
> [ 17.837345] __mutex_lock+0x8c/0x420
> [ 17.837354] mutex_lock_nested+0x34/0x40
> [ 17.837360] clk_prepare_lock+0x54/0xb0
> [ 17.837367] clk_unprepare+0x2c/0x50
> [ 17.837373] clk_bulk_unprepare+0x44/0x60
> [ 17.837380] imx8mp_blk_ctrl_power_off+0xb4/0x100
> [ 17.837386] _genpd_power_off+0x9c/0x180
> [ 17.837392] genpd_power_off.part.0.isra.0+0x130/0x2a0
> [ 17.837399] genpd_power_off_work_fn+0x6c/0x90
> [ 17.837405] process_one_work+0x294/0x6b0
> [ 17.837412] worker_thread+0x7c/0x450
> [ 17.837416] kthread+0x114/0x120
> [ 17.837424] ret_from_fork+0x10/0x20
> [ 17.837431]
> [ 17.837431] -> #0 (&blk_ctrl_genpd_lock_class){+.+.}-{3:3}:
> [ 17.837442] __lock_acquire+0x1148/0x1910
> [ 17.837448] lock_acquire.part.0+0xec/0x260
> [ 17.837454] lock_acquire+0x68/0x90
> [ 17.837459] __mutex_lock+0x8c/0x420
> [ 17.837466] mutex_lock_nested+0x34/0x40
> [ 17.837472] genpd_lock_mtx+0x20/0x30
> [ 17.837478] genpd_runtime_resume+0xfc/0x2e0
> [ 17.837484] __rpm_callback+0x50/0x1b0
> [ 17.837492] rpm_callback+0x74/0x80
> [ 17.837499] rpm_resume+0x434/0x6e0
> [ 17.837505] __pm_runtime_resume+0x54/0xa0
> [ 17.837512] clk_pm_runtime_get.part.0.isra.0+0x24/0xa0
> [ 17.837518] clk_core_set_rate_nolock+0xbc/0x2b0
> [ 17.837524] clk_set_rate+0x40/0xa0
> [ 17.837529] lcdif_crtc_atomic_enable+0x98/0x880 [imx_lcdif]
> [ 17.837544] drm_atomic_helper_commit_modeset_enables+0xac/0x2b0
> [ 17.837551] drm_atomic_helper_commit_tail_rpm+0x58/0xb0
> [ 17.837558] commit_tail+0xac/0x1a0
> [ 17.837563] drm_atomic_helper_commit+0x1a0/0x1c0
> [ 17.837569] drm_atomic_commit+0x94/0x130
> [ 17.837574] drm_client_modeset_commit_atomic+0x230/0x2a0
> [ 17.837582] drm_client_modeset_commit_locked+0x68/0x1d0
> [ 17.837588] drm_client_modeset_commit+0x38/0x60
> [ 17.837594] drm_fb_helper_set_par+0xd4/0x130
> [ 17.837600] fbcon_init+0x3d4/0x540
> [ 17.837606] visual_init+0xb8/0x110
> [ 17.837613] do_bind_con_driver.isra.0+0x1c8/0x3a0
> [ 17.837620] do_take_over_console+0x148/0x200
> [ 17.837627] do_fbcon_takeover+0x74/0xf0
> [ 17.837632] fbcon_fb_registered+0x18c/0x200
> [ 17.837637] register_framebuffer+0x1bc/0x2b0
> [ 17.837645] __drm_fb_helper_initial_config_and_unlock+0x338/0x5c0
> [ 17.837650] drm_fbdev_client_hotplug+0xd8/0x1c0
> [ 17.837656] drm_fbdev_generic_setup+0xbc/0x1b0
> [ 17.837661] lcdif_probe+0x2b0/0x310 [imx_lcdif]
> [ 17.837672] platform_probe+0x70/0xf0
> [ 17.837678] really_probe+0xc8/0x3e0
> [ 17.837685] __driver_probe_device+0x84/0x190
> [ 17.837692] driver_probe_device+0x44/0x120
> [ 17.837699] __device_attach_driver+0xc4/0x160
> [ 17.837707] bus_for_each_drv+0x80/0xe0
> [ 17.837713] __device_attach+0xb0/0x1f0
> [ 17.837720] device_initial_probe+0x1c/0x30
> [ 17.837727] bus_probe_device+0xa4/0xb0
> [ 17.837734] deferred_probe_work_func+0xac/0x100
> [ 17.837740] process_one_work+0x294/0x6b0
> [ 17.837746] worker_thread+0x7c/0x450
> [ 17.837751] kthread+0x114/0x120
> [ 17.837758] ret_from_fork+0x10/0x20
> [ 17.837764]
> [ 17.837764] other info that might help us debug this:
> [ 17.837764]
> [ 17.837766] Possible unsafe locking scenario:
> [ 17.837766]
> [ 17.837768] CPU0 CPU1
> [ 17.837770] ---- ----
> [ 17.837772] lock(prepare_lock);
> [ 17.837779] lock(&blk_ctrl_genpd_lock_class);
> [ 17.837785] lock(prepare_lock);
> [ 17.837790] lock(&blk_ctrl_genpd_lock_class);
> [ 17.837796]
> [ 17.837796] *** DEADLOCK ***
> [ 17.837796]
> [ 17.837799] 11 locks held by kworker/u8:6/152:
> [ 17.837803] #0: ffff000000040938 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1fc/0x6b0
> [ 17.837821] #1: ffff80000b74bdd0 (deferred_probe_work){+.+.}-{0:0}, at: process_one_work+0x1fc/0x6b0
> [ 17.837838] #2: ffff0000003f58f8 (&dev->mutex){....}-{3:3}, at: __device_attach+0x40/0x1f0
> [ 17.837856] #3: ffff800009c1ddc0 (registration_lock){+.+.}-{3:3}, at: register_framebuffer+0x4c/0x2b0
> [ 17.837875] #4: ffff800009ae4e68 (console_lock){+.+.}-{0:0}, at: fbcon_fb_registered+0x1f8/0x200
> [ 17.837892] #5: ffff000002f1ee78 (&helper->lock){+.+.}-{3:3}, at: drm_fb_helper_set_par+0x98/0x130
> [ 17.837909] #6: ffff0000038611a8 (&dev->master_mutex){+.+.}-{3:3}, at: drm_master_internal_acquire+0x2c/0x70
> [ 17.837928] #7: ffff000002f1ec98 (&client->modeset_mutex){+.+.}-{3:3}, at: drm_client_modeset_commit_locked+0x34/0x1d0
> [ 17.837947] #8: ffff80000b74b690 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_client_modeset_commit_atomic+0x50/0x2a0
> [ 17.837964] #9: ffff000003863138 (crtc_ww_class_mutex){+.+.}-{3:3}, at: drm_modeset_lock+0x48/0x130
> [ 17.837984] #10: ffff800009c1e5e8 (prepare_lock){+.+.}-{3:3}, at: clk_prepare_lock+0x34/0xb0
> [ 17.838003]
> [ 17.838003] stack backtrace:
> [ 17.838007] CPU: 1 PID: 152 Comm: kworker/u8:6 Not tainted 6.1.0-rc2-00199-gd504fb27855a-dirty #301
> [ 17.838013] Hardware name: Polyhex Debix Model A i.MX8MPlus board (DT)
> [ 17.838018] Workqueue: events_unbound deferred_probe_work_func
> [ 17.838029] Call trace:
> [ 17.838031] dump_backtrace+0xe4/0x140
> [ 17.838042] show_stack+0x20/0x50
> [ 17.838049] dump_stack_lvl+0x9c/0xd8
> [ 17.838055] dump_stack+0x18/0x34
> [ 17.838060] print_circular_bug+0x1f8/0x200
> [ 17.838066] check_noncircular+0x160/0x180
> [ 17.838072] __lock_acquire+0x1148/0x1910
> [ 17.838078] lock_acquire.part.0+0xec/0x260
> [ 17.838084] lock_acquire+0x68/0x90
> [ 17.838089] __mutex_lock+0x8c/0x420
> [ 17.838098] mutex_lock_nested+0x34/0x40
> [ 17.838104] genpd_lock_mtx+0x20/0x30
> [ 17.838110] genpd_runtime_resume+0xfc/0x2e0
> [ 17.838117] __rpm_callback+0x50/0x1b0
> [ 17.838125] rpm_callback+0x74/0x80
> [ 17.838132] rpm_resume+0x434/0x6e0
> [ 17.838138] __pm_runtime_resume+0x54/0xa0
> [ 17.838145] clk_pm_runtime_get.part.0.isra.0+0x24/0xa0
> [ 17.838150] clk_core_set_rate_nolock+0xbc/0x2b0
> [ 17.838157] clk_set_rate+0x40/0xa0
> [ 17.838162] lcdif_crtc_atomic_enable+0x98/0x880 [imx_lcdif]
> [ 17.838175] drm_atomic_helper_commit_modeset_enables+0xac/0x2b0
> [ 17.838182] drm_atomic_helper_commit_tail_rpm+0x58/0xb0
> [ 17.838188] commit_tail+0xac/0x1a0
> [ 17.838194] drm_atomic_helper_commit+0x1a0/0x1c0
> [ 17.838200] drm_atomic_commit+0x94/0x130
> [ 17.838205] drm_client_modeset_commit_atomic+0x230/0x2a0
> [ 17.838212] drm_client_modeset_commit_locked+0x68/0x1d0
> [ 17.838218] drm_client_modeset_commit+0x38/0x60
> [ 17.838224] drm_fb_helper_set_par+0xd4/0x130
> [ 17.838230] fbcon_init+0x3d4/0x540
> [ 17.838235] visual_init+0xb8/0x110
> [ 17.838243] do_bind_con_driver.isra.0+0x1c8/0x3a0
> [ 17.838250] do_take_over_console+0x148/0x200
> [ 17.838257] do_fbcon_takeover+0x74/0xf0
> [ 17.838262] fbcon_fb_registered+0x18c/0x200
> [ 17.838268] register_framebuffer+0x1bc/0x2b0
> [ 17.838275] __drm_fb_helper_initial_config_and_unlock+0x338/0x5c0
> [ 17.838282] drm_fbdev_client_hotplug+0xd8/0x1c0
> [ 17.838288] drm_fbdev_generic_setup+0xbc/0x1b0
> [ 17.838293] lcdif_probe+0x2b0/0x310 [imx_lcdif]
> [ 17.838304] platform_probe+0x70/0xf0
> [ 17.838309] really_probe+0xc8/0x3e0
> [ 17.838316] __driver_probe_device+0x84/0x190
> [ 17.838323] driver_probe_device+0x44/0x120
> [ 17.838330] __device_attach_driver+0xc4/0x160
> [ 17.838338] bus_for_each_drv+0x80/0xe0
> [ 17.838344] __device_attach+0xb0/0x1f0
> [ 17.838351] device_initial_probe+0x1c/0x30
> [ 17.838358] bus_probe_device+0xa4/0xb0
> [ 17.838365] deferred_probe_work_func+0xac/0x100
> [ 17.838372] process_one_work+0x294/0x6b0
> [ 17.838378] worker_thread+0x7c/0x450
> [ 17.838383] kthread+0x114/0x120
> [ 17.838390] ret_from_fork+0x10/0x20
Let's see if this works any better:
https://patchwork.kernel.org/project/linux-pm/list/?series=693012
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