Hi Serge,
I noticed that on various Cherry Trail (x86) based
devices, which use a 8250_dw UART for their blue-tooth,
I'm now (with 5.9) seeing a lockdep warning on suspend/resume",
see below.
This is caused by commit cc816969d7b5 ("serial: 8250_dw: Fix common
clocks usage race condition"). If I revert that commit the lockdep
warning goes away.
Regards,
Hans
Here is the promised lockdep output:
[ 843.852886] ======================================================
[ 843.852888] WARNING: possible circular locking dependency detected
[ 843.852894] 5.9.0-rc3+ #38 Tainted: G W E
[ 843.852896] ------------------------------------------------------
[ 843.852900] systemd-sleep/1628 is trying to acquire lock:
[ 843.852905] ffff935e30344d80 ((work_completion)(&data->clk_work)){+.+.}-{0:0}, at: __flush_work+0x2e6/0x460
[ 843.852922]
but task is already holding lock:
[ 843.852924] ffff935e302f1420 (&port->mutex){+.+.}-{3:3}, at: uart_suspend_port+0x3f/0x1f0
[ 843.852938]
which lock already depends on the new lock.
[ 843.852940]
the existing dependency chain (in reverse order) is:
[ 843.852943]
-> #1 (&port->mutex){+.+.}-{3:3}:
[ 843.852954] __mutex_lock+0x7b/0x820
[ 843.852959] serial8250_update_uartclk+0x34/0x1b0
[ 843.852965] process_one_work+0x23f/0x570
[ 843.852969] worker_thread+0x55/0x3c0
[ 843.852974] kthread+0x138/0x160
[ 843.852981] ret_from_fork+0x22/0x30
[ 843.852984]
-> #0 ((work_completion)(&data->clk_work)){+.+.}-{0:0}:
[ 843.852995] __lock_acquire+0x1238/0x2080
[ 843.852999] lock_acquire+0xa7/0x3d0
[ 843.853003] __flush_work+0x30d/0x460
[ 843.853008] uart_suspend_port+0x1b9/0x1f0
[ 843.853014] dw8250_suspend+0x10/0x20
[ 843.853020] dpm_run_callback+0x51/0xc0
[ 843.853025] __device_suspend+0x1f9/0x450
[ 843.853029] dpm_suspend+0x13d/0x1e0
[ 843.853033] dpm_suspend_start+0x77/0x80
[ 843.853040] suspend_devices_and_enter+0xe6/0x620
[ 843.853044] pm_suspend.cold+0x333/0x389
[ 843.853048] state_store+0x71/0xd0
[ 843.853056] kernfs_fop_write+0xdc/0x1c0
[ 843.853063] vfs_write+0xec/0x230
[ 843.853068] ksys_write+0x58/0xd0
[ 843.853075] do_syscall_64+0x33/0x40
[ 843.853079] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 843.853081]
other info that might help us debug this:
[ 843.853083] Possible unsafe locking scenario:
[ 843.853087] CPU0 CPU1
[ 843.853090] ---- ----
[ 843.853091] lock(&port->mutex);
[ 843.853095] lock((work_completion)(&data->clk_work));
[ 843.853098] lock(&port->mutex);
[ 843.853101] lock((work_completion)(&data->clk_work));
[ 843.853105]
*** DEADLOCK ***
[ 843.853109] 7 locks held by systemd-sleep/1628:
[ 843.853111] #0: ffff935e302a9488 (sb_writers#4){.+.+}-{0:0}, at: vfs_write+0x1a0/0x230
[ 843.853123] #1: ffff935e0e56a290 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write+0xa5/0x1c0
[ 843.853134] #2: ffff935e392a7848 (kn->active#206){.+.+}-{0:0}, at: kernfs_fop_write+0xad/0x1c0
[ 843.853144] #3: ffffffffb487b0b0 (system_transition_mutex){+.+.}-{3:3}, at: pm_suspend.cold+0xee/0x389
[ 843.853155] #4: ffffffffb4a42370 (acpi_scan_lock){+.+.}-{3:3}, at: acpi_s2idle_begin+0xa/0x10
[ 843.853167] #5: ffff935e39ee29a0 (&dev->mutex){....}-{3:3}, at: __device_suspend+0xe8/0x450
[ 843.853178] #6: ffff935e302f1420 (&port->mutex){+.+.}-{3:3}, at: uart_suspend_port+0x3f/0x1f0
[ 843.853187]
stack backtrace:
[ 843.853195] CPU: 3 PID: 1628 Comm: systemd-sleep Tainted: G W E 5.9.0-rc3+ #38
[ 843.853199] Hardware name: Acer One S1003/One S1003, BIOS V1.19 03/20/2018
[ 843.853203] Call Trace:
[ 843.853213] dump_stack+0x8b/0xb8
[ 843.853222] check_noncircular+0x134/0x150
[ 843.853234] __lock_acquire+0x1238/0x2080
[ 843.853244] ? lock_acquire+0xa7/0x3d0
[ 843.853252] lock_acquire+0xa7/0x3d0
[ 843.853257] ? __flush_work+0x2e6/0x460
[ 843.853265] ? lockdep_hardirqs_on_prepare+0x116/0x190
[ 843.853270] ? asm_sysvec_apic_timer_interrupt+0x12/0x20
[ 843.853276] ? trace_hardirqs_on+0x1c/0xe0
[ 843.853284] __flush_work+0x30d/0x460
[ 843.853289] ? __flush_work+0x2e6/0x460
[ 843.853295] ? sched_clock+0x5/0x10
[ 843.853300] ? sched_clock_cpu+0xc/0xb0
[ 843.853311] ? __mutex_unlock_slowpath+0x35/0x270
[ 843.853321] ? clk_notifier_unregister+0xf8/0x120
[ 843.853328] uart_suspend_port+0x1b9/0x1f0
[ 843.853337] ? acpi_pm_notify_work_func+0x30/0x30
[ 843.853342] dw8250_suspend+0x10/0x20
[ 843.853346] dpm_run_callback+0x51/0xc0
[ 843.853353] __device_suspend+0x1f9/0x450
[ 843.853360] dpm_suspend+0x13d/0x1e0
[ 843.853367] dpm_suspend_start+0x77/0x80
[ 843.853373] suspend_devices_and_enter+0xe6/0x620
[ 843.853381] ? rcu_read_lock_sched_held+0x3f/0x80
[ 843.853388] pm_suspend.cold+0x333/0x389
[ 843.853394] state_store+0x71/0xd0
[ 843.853405] kernfs_fop_write+0xdc/0x1c0
[ 843.853413] vfs_write+0xec/0x230
[ 843.853420] ksys_write+0x58/0xd0
[ 843.853427] do_syscall_64+0x33/0x40
[ 843.853432] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 843.853441] RIP: 0033:0x7f2a99d184b7
[ 843.853450] Code: 0d 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24
[ 843.853453] RSP: 002b:00007ffedaca0ef8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[ 843.853459] RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007f2a99d184b7
[ 843.853462] RDX: 0000000000000004 RSI: 00007ffedaca0fe0 RDI: 0000000000000004
[ 843.853465] RBP: 00007ffedaca0fe0 R08: 000000000000c0d0 R09: 00007f2a99daf0c0
[ 843.853468] R10: 00007f2a99daefc0 R11: 0000000000000246 R12: 0000000000000004
[ 843.853471] R13: 000055f1a8c67330 R14: 0000000000000004 R15: 00007f2a99dec720
