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Message-ID: <5751F267.50803@gmail.com>
Date: Fri, 3 Jun 2016 14:11:03 -0700
From: Florian Fainelli <f.fainelli@...il.com>
To: Andrew Lunn <andrew@...n.ch>, David Miller <davem@...emloft.net>,
Vivien Didelot <vivien.didelot@...oirfairelinux.com>
Cc: netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 02/17] net: dsa: mv88e6xxx: fix circular lock in
PPU work
On 06/03/2016 09:44 AM, Andrew Lunn wrote:
> From: Vivien Didelot <vivien.didelot@...oirfairelinux.com>
>
> Lock debugging shows that there is a possible circular lock in the PPU
> work code. Switch the lock order of smi_mutex and ppu_mutex to fix this.
>
> Here's the full trace:
>
> [ 4.341325] ======================================================
> [ 4.347519] [ INFO: possible circular locking dependency detected ]
> [ 4.353800] 4.6.0 #4 Not tainted
> [ 4.357039] -------------------------------------------------------
> [ 4.363315] kworker/0:1/328 is trying to acquire lock:
> [ 4.368463] (&ps->smi_mutex){+.+.+.}, at: [<8049c758>] mv88e6xxx_reg_read+0x30/0x54
> [ 4.376313]
> [ 4.376313] but task is already holding lock:
> [ 4.382160] (&ps->ppu_mutex){+.+...}, at: [<8049cac0>] mv88e6xxx_ppu_reenable_work+0x28/0xd4
> [ 4.390772]
> [ 4.390772] which lock already depends on the new lock.
> [ 4.390772]
> [ 4.398963]
> [ 4.398963] the existing dependency chain (in reverse order) is:
> [ 4.406461]
> [ 4.406461] -> #1 (&ps->ppu_mutex){+.+...}:
> [ 4.410897] [<806d86bc>] mutex_lock_nested+0x54/0x360
> [ 4.416606] [<8049a800>] mv88e6xxx_ppu_access_get+0x28/0x100
> [ 4.422906] [<8049b778>] mv88e6xxx_phy_read+0x90/0xdc
> [ 4.428599] [<806a4534>] dsa_slave_phy_read+0x3c/0x40
> [ 4.434300] [<804943ec>] mdiobus_read+0x68/0x80
> [ 4.439481] [<804939d4>] get_phy_device+0x58/0x1d8
> [ 4.444914] [<80493ed0>] mdiobus_scan+0x24/0xf4
> [ 4.450078] [<8049409c>] __mdiobus_register+0xfc/0x1ac
> [ 4.455857] [<806a40b0>] dsa_probe+0x860/0xca8
> [ 4.460934] [<8043246c>] platform_drv_probe+0x5c/0xc0
> [ 4.466627] [<804305a0>] driver_probe_device+0x118/0x450
> [ 4.472589] [<80430b00>] __device_attach_driver+0xac/0x128
> [ 4.478724] [<8042e350>] bus_for_each_drv+0x74/0xa8
> [ 4.484235] [<804302d8>] __device_attach+0xc4/0x154
> [ 4.489755] [<80430cec>] device_initial_probe+0x1c/0x20
> [ 4.495612] [<8042f620>] bus_probe_device+0x98/0xa0
> [ 4.501123] [<8042fbd0>] deferred_probe_work_func+0x4c/0xd4
> [ 4.507328] [<8013a794>] process_one_work+0x1a8/0x604
> [ 4.513030] [<8013ac54>] worker_thread+0x64/0x528
> [ 4.518367] [<801409e8>] kthread+0xec/0x100
> [ 4.523201] [<80108f30>] ret_from_fork+0x14/0x24
> [ 4.528462]
> [ 4.528462] -> #0 (&ps->smi_mutex){+.+.+.}:
> [ 4.532895] [<8015ad5c>] lock_acquire+0xb4/0x1dc
> [ 4.538154] [<806d86bc>] mutex_lock_nested+0x54/0x360
> [ 4.543856] [<8049c758>] mv88e6xxx_reg_read+0x30/0x54
> [ 4.549549] [<8049cad8>] mv88e6xxx_ppu_reenable_work+0x40/0xd4
> [ 4.556022] [<8013a794>] process_one_work+0x1a8/0x604
> [ 4.561707] [<8013ac54>] worker_thread+0x64/0x528
> [ 4.567053] [<801409e8>] kthread+0xec/0x100
> [ 4.571878] [<80108f30>] ret_from_fork+0x14/0x24
> [ 4.577139]
> [ 4.577139] other info that might help us debug this:
> [ 4.577139]
> [ 4.585159] Possible unsafe locking scenario:
> [ 4.585159]
> [ 4.591093] CPU0 CPU1
> [ 4.595631] ---- ----
> [ 4.600169] lock(&ps->ppu_mutex);
> [ 4.603693] lock(&ps->smi_mutex);
> [ 4.609742] lock(&ps->ppu_mutex);
> [ 4.615790] lock(&ps->smi_mutex);
> [ 4.619314]
> [ 4.619314] *** DEADLOCK ***
> [ 4.619314]
> [ 4.625256] 3 locks held by kworker/0:1/328:
> [ 4.629537] #0: ("events"){.+.+..}, at: [<8013a704>] process_one_work+0x118/0x604
> [ 4.637288] #1: ((&ps->ppu_work)){+.+...}, at: [<8013a704>] process_one_work+0x118/0x604
> [ 4.645653] #2: (&ps->ppu_mutex){+.+...}, at: [<8049cac0>] mv88e6xxx_ppu_reenable_work+0x28/0xd4
> [ 4.654714]
> [ 4.654714] stack backtrace:
> [ 4.659098] CPU: 0 PID: 328 Comm: kworker/0:1 Not tainted 4.6.0 #4
> [ 4.665286] Hardware name: Freescale Vybrid VF5xx/VF6xx (Device Tree)
> [ 4.671748] Workqueue: events mv88e6xxx_ppu_reenable_work
> [ 4.677174] Backtrace:
> [ 4.679674] [<8010d354>] (dump_backtrace) from [<8010d5a0>] (show_stack+0x20/0x24)
> [ 4.687252] r6:80fb3c88 r5:80fb3c88 r4:80fb4728 r3:00000002
> [ 4.693003] [<8010d580>] (show_stack) from [<803b45e8>] (dump_stack+0x24/0x28)
> [ 4.700246] [<803b45c4>] (dump_stack) from [<80157398>] (print_circular_bug+0x208/0x32c)
> [ 4.708361] [<80157190>] (print_circular_bug) from [<8015a630>] (__lock_acquire+0x185c/0x1b80)
> [ 4.716982] r10:9ec22a00 r9:00000060 r8:8164b6bc r7:00000040 r6:00000003 r5:8163a5b4
> [ 4.724905] r4:00000003 r3:9ec22de8
> [ 4.728537] [<80158dd4>] (__lock_acquire) from [<8015ad5c>] (lock_acquire+0xb4/0x1dc)
> [ 4.736378] r10:60000013 r9:00000000 r8:00000000 r7:00000000 r6:9e5e9c50 r5:80e618e0
> [ 4.744301] r4:00000000
> [ 4.746879] [<8015aca8>] (lock_acquire) from [<806d86bc>] (mutex_lock_nested+0x54/0x360)
> [ 4.754976] r10:9e5e9c1c r9:80e616c4 r8:9f685ea0 r7:0000001b r6:9ec22a00 r5:8163a5b4
> [ 4.762899] r4:9e5e9c1c
> [ 4.765477] [<806d8668>] (mutex_lock_nested) from [<8049c758>] (mv88e6xxx_reg_read+0x30/0x54)
> [ 4.774008] r10:80e60c5b r9:80e616c4 r8:9f685ea0 r7:0000001b r6:00000004 r5:9e5e9c10
> [ 4.781930] r4:9e5e9c1c
> [ 4.784507] [<8049c728>] (mv88e6xxx_reg_read) from [<8049cad8>] (mv88e6xxx_ppu_reenable_work+0x40/0xd4)
> [ 4.793907] r7:9ffd5400 r6:9e5e9c68 r5:9e5e9cb0 r4:9e5e9c10
> [ 4.799659] [<8049ca98>] (mv88e6xxx_ppu_reenable_work) from [<8013a794>] (process_one_work+0x1a8/0x604)
> [ 4.809059] r9:80e616c4 r8:9f685ea0 r7:9ffd5400 r6:80e0a1c8 r5:9f5f2e80 r4:9e5e9cb0
> [ 4.816910] [<8013a5ec>] (process_one_work) from [<8013ac54>] (worker_thread+0x64/0x528)
> [ 4.825010] r10:9f5f2e80 r9:00000008 r8:80e0dc80 r7:80e0a1fc r6:80e0a1c8 r5:9f5f2e98
> [ 4.832933] r4:80e0a1c8
> [ 4.835510] [<8013abf0>] (worker_thread) from [<801409e8>] (kthread+0xec/0x100)
> [ 4.842827] r10:00000000 r9:00000000 r8:00000000 r7:8013abf0 r6:9f5f2e80 r5:9ec15740
> [ 4.850749] r4:00000000
> [ 4.853327] [<801408fc>] (kthread) from [<80108f30>] (ret_from_fork+0x14/0x24)
> [ 4.860557] r7:00000000 r6:00000000 r5:801408fc r4:9ec15740
>
> Signed-off-by: Vivien Didelot <vivien.didelot@...oirfairelinux.com>
Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
--
Florian
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