| Message ID | 20220616112550.877118-1-o.rempel@pengutronix.de (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 7a49f2193063b7db60a964fc26774275a4c964cd |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net-next,v1,1/1] net: dsa: ar9331: fix potential dead lock on mdio access | expand |
> static int ar9331_mdio_read(void *ctx, const void *reg_buf, size_t reg_len, > @@ -849,6 +849,8 @@ static int ar9331_mdio_read(void *ctx, const void *reg_buf, size_t reg_len, > return 0; > } > > + mutex_lock_nested(&sbus->mdio_lock, MDIO_MUTEX_NESTED); > + Do you know about mdiobus_read_nested() and mdiobus_write_nested(). The mv88e6xxx driver uses these. Andrew
On Thu, Jun 16, 2022 at 03:34:18PM +0200, Andrew Lunn wrote: > > static int ar9331_mdio_read(void *ctx, const void *reg_buf, size_t reg_len, > > @@ -849,6 +849,8 @@ static int ar9331_mdio_read(void *ctx, const void *reg_buf, size_t reg_len, > > return 0; > > } > > > > + mutex_lock_nested(&sbus->mdio_lock, MDIO_MUTEX_NESTED); > > + > > Do you know about mdiobus_read_nested() and > mdiobus_write_nested(). The mv88e6xxx driver uses these. Yes. I need at least 2 master MDIO accesses to implement 1 slave mdio access. So I decided to get lock one time for all needed accesses instead of taking it multiple times. Regards, Oleksij
Hello: This patch was applied to netdev/net-next.git (master) by Jakub Kicinski <kuba@kernel.org>: On Thu, 16 Jun 2022 13:25:50 +0200 you wrote: > Rework MDIO locking to avoid potential circular locking: > > WARNING: possible circular locking dependency detected > 5.19.0-rc1-ar9331-00017-g3ab364c7c48c #5 Not tainted > ------------------------------------------------------ > kworker/u2:4/68 is trying to acquire lock: > 81f3c83c (ar9331:1005:(&ar9331_mdio_regmap_config)->lock){+.+.}-{4:4}, at: regmap_write+0x50/0x8c > > [...] Here is the summary with links: - [net-next,v1,1/1] net: dsa: ar9331: fix potential dead lock on mdio access https://git.kernel.org/netdev/net-next/c/7a49f2193063 You are awesome, thank you!
diff --git a/drivers/net/dsa/qca/ar9331.c b/drivers/net/dsa/qca/ar9331.c index e5098cfe44bc..f23ce56fa591 100644 --- a/drivers/net/dsa/qca/ar9331.c +++ b/drivers/net/dsa/qca/ar9331.c @@ -818,7 +818,7 @@ static int __ar9331_mdio_write(struct mii_bus *sbus, u8 mode, u16 reg, u16 val) FIELD_GET(AR9331_SW_LOW_ADDR_PHY, reg); r = FIELD_GET(AR9331_SW_LOW_ADDR_REG, reg); - return mdiobus_write(sbus, p, r, val); + return __mdiobus_write(sbus, p, r, val); } static int __ar9331_mdio_read(struct mii_bus *sbus, u16 reg) @@ -829,7 +829,7 @@ static int __ar9331_mdio_read(struct mii_bus *sbus, u16 reg) FIELD_GET(AR9331_SW_LOW_ADDR_PHY, reg); r = FIELD_GET(AR9331_SW_LOW_ADDR_REG, reg); - return mdiobus_read(sbus, p, r); + return __mdiobus_read(sbus, p, r); } static int ar9331_mdio_read(void *ctx, const void *reg_buf, size_t reg_len, @@ -849,6 +849,8 @@ static int ar9331_mdio_read(void *ctx, const void *reg_buf, size_t reg_len, return 0; } + mutex_lock_nested(&sbus->mdio_lock, MDIO_MUTEX_NESTED); + ret = __ar9331_mdio_read(sbus, reg); if (ret < 0) goto error; @@ -860,9 +862,13 @@ static int ar9331_mdio_read(void *ctx, const void *reg_buf, size_t reg_len, *(u32 *)val_buf |= ret << 16; + mutex_unlock(&sbus->mdio_lock); + return 0; error: + mutex_unlock(&sbus->mdio_lock); dev_err_ratelimited(&sbus->dev, "Bus error. Failed to read register.\n"); + return ret; } @@ -872,12 +878,15 @@ static int ar9331_mdio_write(void *ctx, u32 reg, u32 val) struct mii_bus *sbus = priv->sbus; int ret; + mutex_lock_nested(&sbus->mdio_lock, MDIO_MUTEX_NESTED); if (reg == AR9331_SW_REG_PAGE) { ret = __ar9331_mdio_write(sbus, AR9331_SW_MDIO_PHY_MODE_PAGE, 0, val); if (ret < 0) goto error; + mutex_unlock(&sbus->mdio_lock); + return 0; } @@ -897,10 +906,14 @@ static int ar9331_mdio_write(void *ctx, u32 reg, u32 val) if (ret < 0) goto error; + mutex_unlock(&sbus->mdio_lock); + return 0; error: + mutex_unlock(&sbus->mdio_lock); dev_err_ratelimited(&sbus->dev, "Bus error. Failed to write register.\n"); + return ret; }
Rework MDIO locking to avoid potential circular locking: WARNING: possible circular locking dependency detected 5.19.0-rc1-ar9331-00017-g3ab364c7c48c #5 Not tainted ------------------------------------------------------ kworker/u2:4/68 is trying to acquire lock: 81f3c83c (ar9331:1005:(&ar9331_mdio_regmap_config)->lock){+.+.}-{4:4}, at: regmap_write+0x50/0x8c but task is already holding lock: 81f60494 (&bus->mdio_lock){+.+.}-{4:4}, at: mdiobus_read+0x40/0x78 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&bus->mdio_lock){+.+.}-{4:4}: lock_acquire+0x2d4/0x360 __mutex_lock+0xf8/0x384 mutex_lock_nested+0x2c/0x38 mdiobus_write+0x44/0x80 ar9331_sw_bus_write+0x50/0xe4 _regmap_raw_write_impl+0x604/0x724 _regmap_bus_raw_write+0x9c/0xb4 _regmap_write+0xdc/0x1a0 _regmap_update_bits+0xf4/0x118 _regmap_select_page+0x108/0x138 _regmap_raw_read+0x25c/0x288 _regmap_bus_read+0x60/0x98 _regmap_read+0xd4/0x1b0 _regmap_update_bits+0xc4/0x118 regmap_update_bits_base+0x64/0x8c ar9331_sw_irq_bus_sync_unlock+0x40/0x6c __irq_set_handler+0x7c/0xac ar9331_sw_irq_map+0x48/0x7c irq_domain_associate+0x174/0x208 irq_create_mapping_affinity+0x1a8/0x230 ar9331_sw_probe+0x22c/0x388 mdio_probe+0x44/0x70 really_probe+0x200/0x424 __driver_probe_device+0x290/0x298 driver_probe_device+0x54/0xe4 __device_attach_driver+0xe4/0x130 bus_for_each_drv+0xb4/0xd8 __device_attach+0x104/0x1a4 bus_probe_device+0x48/0xc4 device_add+0x600/0x800 mdio_device_register+0x68/0xa0 of_mdiobus_register+0x2bc/0x3c4 ag71xx_probe+0x6e4/0x984 platform_probe+0x78/0xd0 really_probe+0x200/0x424 __driver_probe_device+0x290/0x298 driver_probe_device+0x54/0xe4 __driver_attach+0x17c/0x190 bus_for_each_dev+0x8c/0xd0 bus_add_driver+0x110/0x228 driver_register+0xe4/0x12c do_one_initcall+0x104/0x2a0 kernel_init_freeable+0x250/0x288 kernel_init+0x34/0x130 ret_from_kernel_thread+0x14/0x1c -> #0 (ar9331:1005:(&ar9331_mdio_regmap_config)->lock){+.+.}-{4:4}: check_noncircular+0x88/0xc0 __lock_acquire+0x10bc/0x18bc lock_acquire+0x2d4/0x360 __mutex_lock+0xf8/0x384 mutex_lock_nested+0x2c/0x38 regmap_write+0x50/0x8c ar9331_sw_mbus_read+0x74/0x1b8 __mdiobus_read+0x90/0xec mdiobus_read+0x50/0x78 get_phy_device+0xa0/0x18c fwnode_mdiobus_register_phy+0x120/0x1d4 of_mdiobus_register+0x244/0x3c4 devm_of_mdiobus_register+0xe8/0x100 ar9331_sw_setup+0x16c/0x3a0 dsa_register_switch+0x7dc/0xcc0 ar9331_sw_probe+0x370/0x388 mdio_probe+0x44/0x70 really_probe+0x200/0x424 __driver_probe_device+0x290/0x298 driver_probe_device+0x54/0xe4 __device_attach_driver+0xe4/0x130 bus_for_each_drv+0xb4/0xd8 __device_attach+0x104/0x1a4 bus_probe_device+0x48/0xc4 deferred_probe_work_func+0xf0/0x10c process_one_work+0x314/0x4d4 worker_thread+0x2a4/0x354 kthread+0x134/0x13c ret_from_kernel_thread+0x14/0x1c other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&bus->mdio_lock); lock(ar9331:1005:(&ar9331_mdio_regmap_config)->lock); lock(&bus->mdio_lock); lock(ar9331:1005:(&ar9331_mdio_regmap_config)->lock); *** DEADLOCK *** 5 locks held by kworker/u2:4/68: #0: 81c04eb4 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1e4/0x4d4 #1: 81f0de78 (deferred_probe_work){+.+.}-{0:0}, at: process_one_work+0x1e4/0x4d4 #2: 81f0a880 (&dev->mutex){....}-{4:4}, at: __device_attach+0x40/0x1a4 #3: 80c8aee0 (dsa2_mutex){+.+.}-{4:4}, at: dsa_register_switch+0x5c/0xcc0 #4: 81f60494 (&bus->mdio_lock){+.+.}-{4:4}, at: mdiobus_read+0x40/0x78 stack backtrace: CPU: 0 PID: 68 Comm: kworker/u2:4 Not tainted 5.19.0-rc1-ar9331-00017-g3ab364c7c48c #5 Workqueue: events_unbound deferred_probe_work_func Stack : 00000056 800d4638 81f0d64c 00000004 00000018 00000000 80a20000 80a20000 80937590 81ef3858 81f0d760 3913578a 00000005 8045e824 81f0d600 a8db84cc 00000000 00000000 80937590 00000a44 00000000 00000002 00000001 ffffffff 81f0d6a4 80982d7c 0000000f 20202020 80a20000 00000001 80937590 81ef3858 81f0d760 3913578a 00000005 00000005 00000000 03bd0000 00000000 80e00000 ... Call Trace: [<80069db0>] show_stack+0x94/0x130 [<8045e824>] dump_stack_lvl+0x54/0x8c [<800c7fac>] check_noncircular+0x88/0xc0 [<800ca068>] __lock_acquire+0x10bc/0x18bc [<800cb478>] lock_acquire+0x2d4/0x360 [<807b84c4>] __mutex_lock+0xf8/0x384 [<807b877c>] mutex_lock_nested+0x2c/0x38 [<804ea640>] regmap_write+0x50/0x8c [<80501e38>] ar9331_sw_mbus_read+0x74/0x1b8 [<804fe9a0>] __mdiobus_read+0x90/0xec [<804feac4>] mdiobus_read+0x50/0x78 [<804fcf74>] get_phy_device+0xa0/0x18c [<804ffeb4>] fwnode_mdiobus_register_phy+0x120/0x1d4 [<805004f0>] of_mdiobus_register+0x244/0x3c4 [<804f0c50>] devm_of_mdiobus_register+0xe8/0x100 [<805017a0>] ar9331_sw_setup+0x16c/0x3a0 [<807355c8>] dsa_register_switch+0x7dc/0xcc0 [<80501468>] ar9331_sw_probe+0x370/0x388 [<804ff0c0>] mdio_probe+0x44/0x70 [<804d1848>] really_probe+0x200/0x424 [<804d1cfc>] __driver_probe_device+0x290/0x298 [<804d1d58>] driver_probe_device+0x54/0xe4 [<804d2298>] __device_attach_driver+0xe4/0x130 [<804cf048>] bus_for_each_drv+0xb4/0xd8 [<804d200c>] __device_attach+0x104/0x1a4 [<804d026c>] bus_probe_device+0x48/0xc4 [<804d108c>] deferred_probe_work_func+0xf0/0x10c [<800a0ffc>] process_one_work+0x314/0x4d4 [<800a17fc>] worker_thread+0x2a4/0x354 [<800a9a54>] kthread+0x134/0x13c [<8006306c>] ret_from_kernel_thread+0x14/0x1c [ Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de> --- drivers/net/dsa/qca/ar9331.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-)