From: Dmitry Baryshkov Date: Thu, 5 Jun 2025 11:25:49 +0000 (+0300) Subject: phy: use per-PHY lockdep keys X-Git-Tag: v6.16-rc7~33^2~1 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=cf0233491b3a15933234a26efd9ecbc1c0764674;p=thirdparty%2Flinux.git phy: use per-PHY lockdep keys If the PHY driver uses another PHY internally (e.g. in case of eUSB2, repeaters are represented as PHYs), then it would trigger the following lockdep splat because all PHYs use a single static lockdep key and thus lockdep can not identify whether there is a dependency or not and reports a false positive. Make PHY subsystem use dynamic lockdep keys, assigning each driver a separate key. This way lockdep can correctly identify dependency graph between mutexes. ============================================ WARNING: possible recursive locking detected 6.15.0-rc7-next-20250522-12896-g3932f283970c #3455 Not tainted -------------------------------------------- kworker/u51:0/78 is trying to acquire lock: ffff0008116554f0 (&phy->mutex){+.+.}-{4:4}, at: phy_init+0x4c/0x12c but task is already holding lock: ffff000813c10cf0 (&phy->mutex){+.+.}-{4:4}, at: phy_init+0x4c/0x12c other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&phy->mutex); lock(&phy->mutex); *** DEADLOCK *** May be due to missing lock nesting notation 4 locks held by kworker/u51:0/78: #0: ffff000800010948 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x18c/0x5ec #1: ffff80008036bdb0 (deferred_probe_work){+.+.}-{0:0}, at: process_one_work+0x1b4/0x5ec #2: ffff0008094ac8f8 (&dev->mutex){....}-{4:4}, at: __device_attach+0x38/0x188 #3: ffff000813c10cf0 (&phy->mutex){+.+.}-{4:4}, at: phy_init+0x4c/0x12c stack backtrace: CPU: 0 UID: 0 PID: 78 Comm: kworker/u51:0 Not tainted 6.15.0-rc7-next-20250522-12896-g3932f283970c #3455 PREEMPT Hardware name: Qualcomm CRD, BIOS 6.0.240904.BOOT.MXF.2.4-00528.1-HAMOA-1 09/ 4/2024 Workqueue: events_unbound deferred_probe_work_func Call trace: show_stack+0x18/0x24 (C) dump_stack_lvl+0x90/0xd0 dump_stack+0x18/0x24 print_deadlock_bug+0x258/0x348 __lock_acquire+0x10fc/0x1f84 lock_acquire+0x1c8/0x338 __mutex_lock+0xb8/0x59c mutex_lock_nested+0x24/0x30 phy_init+0x4c/0x12c snps_eusb2_hsphy_init+0x54/0x1a0 phy_init+0xe0/0x12c dwc3_core_init+0x450/0x10b4 dwc3_core_probe+0xce4/0x15fc dwc3_probe+0x64/0xb0 platform_probe+0x68/0xc4 really_probe+0xbc/0x298 __driver_probe_device+0x78/0x12c driver_probe_device+0x3c/0x160 __device_attach_driver+0xb8/0x138 bus_for_each_drv+0x84/0xe0 __device_attach+0x9c/0x188 device_initial_probe+0x14/0x20 bus_probe_device+0xac/0xb0 deferred_probe_work_func+0x8c/0xc8 process_one_work+0x208/0x5ec worker_thread+0x1c0/0x368 kthread+0x14c/0x20c ret_from_fork+0x10/0x20 Fixes: 3584f6392f09 ("phy: qcom: phy-qcom-snps-eusb2: Add support for eUSB2 repeater") Fixes: e2463559ff1d ("phy: amlogic: Add Amlogic AXG PCIE PHY Driver") Reviewed-by: Neil Armstrong Reviewed-by: Abel Vesa Reported-by: Johan Hovold Link: https://lore.kernel.org/lkml/ZnpoAVGJMG4Zu-Jw@hovoldconsulting.com/ Reviewed-by: Johan Hovold Tested-by: Johan Hovold Signed-off-by: Dmitry Baryshkov Link: https://lore.kernel.org/r/20250605-phy-subinit-v3-1-1e1e849e10cd@oss.qualcomm.com Signed-off-by: Vinod Koul --- diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c index 8e2daea81666..04a5a34e7a95 100644 --- a/drivers/phy/phy-core.c +++ b/drivers/phy/phy-core.c @@ -994,7 +994,8 @@ struct phy *phy_create(struct device *dev, struct device_node *node, } device_initialize(&phy->dev); - mutex_init(&phy->mutex); + lockdep_register_key(&phy->lockdep_key); + mutex_init_with_key(&phy->mutex, &phy->lockdep_key); phy->dev.class = &phy_class; phy->dev.parent = dev; @@ -1259,6 +1260,8 @@ static void phy_release(struct device *dev) dev_vdbg(dev, "releasing '%s'\n", dev_name(dev)); debugfs_remove_recursive(phy->debugfs); regulator_put(phy->pwr); + mutex_destroy(&phy->mutex); + lockdep_unregister_key(&phy->lockdep_key); ida_free(&phy_ida, phy->id); kfree(phy); } diff --git a/include/linux/phy/phy.h b/include/linux/phy/phy.h index 437769e061b7..13add0c2c407 100644 --- a/include/linux/phy/phy.h +++ b/include/linux/phy/phy.h @@ -154,6 +154,7 @@ struct phy_attrs { * @id: id of the phy device * @ops: function pointers for performing phy operations * @mutex: mutex to protect phy_ops + * @lockdep_key: lockdep information for this mutex * @init_count: used to protect when the PHY is used by multiple consumers * @power_count: used to protect when the PHY is used by multiple consumers * @attrs: used to specify PHY specific attributes @@ -165,6 +166,7 @@ struct phy { int id; const struct phy_ops *ops; struct mutex mutex; + struct lock_class_key lockdep_key; int init_count; int power_count; struct phy_attrs attrs;