On Wed, Dec 18, 2024 at 08:59:51PM +0900, Ryo Takakura wrote: > PCI config access is locked with pci_lock which serializes > pci_user/bus_write_config*() and pci_user/bus_read_config*(). > The subsequently invoked vmd_pci_write() and vmd_pci_read() are also > serialized as they are only invoked by them respectively. > > Remove cfg_lock which is taken by vmd_pci_write() and vmd_pci_read() > for their serialization as its already serialized by pci_lock. > > This fixes the spinlock_t(cfg_lock) usage within > raw_spinlock_t(pci_lock) on RT kernels where spinlock_t becomes > sleepable. > > Reported as following: > [ 18.756807] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48 > [ 18.756810] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 1617, name: nodedev-init > [ 18.756810] preempt_count: 1, expected: 0 > [ 18.756811] RCU nest depth: 0, expected: 0 > [ 18.756811] INFO: lockdep is turned off. > [ 18.756812] irq event stamp: 0 > [ 18.756812] hardirqs last enabled at (0): [<0000000000000000>] 0x0 > [ 18.756815] hardirqs last disabled at (0): [<ffffffff864f1fe2>] copy_process+0xa62/0x2d90 > [ 18.756819] softirqs last enabled at (0): [<ffffffff864f1fe2>] copy_process+0xa62/0x2d90 > [ 18.756820] softirqs last disabled at (0): [<0000000000000000>] 0x0 > [ 18.756822] CPU: 3 UID: 0 PID: 1617 Comm: nodedev-init Tainted: G W 6.12.1 #11 > [ 18.756823] Tainted: [W]=WARN > [ 18.756824] Hardware name: Dell Inc. Vostro 3710/0K1D6X, BIOS 1.14.0 06/09/2023 > [ 18.756825] Call Trace: > [ 18.756826] <TASK> > [ 18.756827] dump_stack_lvl+0x9b/0xf0 > [ 18.756830] dump_stack+0x10/0x20 > [ 18.756831] __might_resched+0x158/0x230 > [ 18.756833] rt_spin_lock+0x4e/0x130 > [ 18.756837] ? vmd_pci_read+0x8d/0x100 [vmd] > [ 18.756839] vmd_pci_read+0x8d/0x100 [vmd] > [ 18.756840] pci_user_read_config_byte+0x6f/0xe0 > [ 18.756843] pci_read_config+0xfe/0x290 > [ 18.756845] sysfs_kf_bin_read+0x68/0x90 > [ 18.756847] kernfs_fop_read_iter+0xd7/0x200 > [ 18.756850] vfs_read+0x26d/0x360 > [ 18.756853] ksys_read+0x70/0xf0 > [ 18.756855] __x64_sys_read+0x1a/0x20 > [ 18.756857] x64_sys_call+0x1715/0x20d0 > [ 18.756859] do_syscall_64+0x8f/0x170 > [ 18.756861] ? syscall_exit_to_user_mode+0xcd/0x2c0 > [ 18.756863] ? do_syscall_64+0x9b/0x170 > [ 18.756865] entry_SYSCALL_64_after_hwframe+0x76/0x7e > > Signed-off-by: Ryo Takakura <ryotkkr98@xxxxxxxxx> > --- Reviewed-by: Luis Claudio R. Goncalves <lgoncalv@xxxxxxxxxx> Best regards, Luis > Thanks Luis for feedback! > > Changes since v1: > https://lore.kernel.org/lkml/20241215141321.383144-1-ryotkkr98@xxxxxxxxx/T/ > > - Remove cfg_lock instead of converting it to raw spinlock as suggested > by Sebastian[0]. > > [0] https://lore.kernel.org/linux-rt-users/20230620154434.MosrzRUh@xxxxxxxxxxxxx/ > > --- > drivers/pci/controller/vmd.c | 8 -------- > 1 file changed, 8 deletions(-) > > diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c > index 9d9596947..2be898424 100644 > --- a/drivers/pci/controller/vmd.c > +++ b/drivers/pci/controller/vmd.c > @@ -125,7 +125,6 @@ struct vmd_irq_list { > struct vmd_dev { > struct pci_dev *dev; > > - spinlock_t cfg_lock; > void __iomem *cfgbar; > > int msix_count; > @@ -385,13 +384,11 @@ static int vmd_pci_read(struct pci_bus *bus, unsigned int devfn, int reg, > { > struct vmd_dev *vmd = vmd_from_bus(bus); > void __iomem *addr = vmd_cfg_addr(vmd, bus, devfn, reg, len); > - unsigned long flags; > int ret = 0; > > if (!addr) > return -EFAULT; > > - spin_lock_irqsave(&vmd->cfg_lock, flags); > switch (len) { > case 1: > *value = readb(addr); > @@ -406,7 +403,6 @@ static int vmd_pci_read(struct pci_bus *bus, unsigned int devfn, int reg, > ret = -EINVAL; > break; > } > - spin_unlock_irqrestore(&vmd->cfg_lock, flags); > return ret; > } > > @@ -420,13 +416,11 @@ static int vmd_pci_write(struct pci_bus *bus, unsigned int devfn, int reg, > { > struct vmd_dev *vmd = vmd_from_bus(bus); > void __iomem *addr = vmd_cfg_addr(vmd, bus, devfn, reg, len); > - unsigned long flags; > int ret = 0; > > if (!addr) > return -EFAULT; > > - spin_lock_irqsave(&vmd->cfg_lock, flags); > switch (len) { > case 1: > writeb(value, addr); > @@ -444,7 +438,6 @@ static int vmd_pci_write(struct pci_bus *bus, unsigned int devfn, int reg, > ret = -EINVAL; > break; > } > - spin_unlock_irqrestore(&vmd->cfg_lock, flags); > return ret; > } > > @@ -1009,7 +1002,6 @@ static int vmd_probe(struct pci_dev *dev, const struct pci_device_id *id) > if (features & VMD_FEAT_OFFSET_FIRST_VECTOR) > vmd->first_vec = 1; > > - spin_lock_init(&vmd->cfg_lock); > pci_set_drvdata(dev, vmd); > err = vmd_enable_domain(vmd, features); > if (err) > -- > 2.34.1 > ---end quoted text---
