From 93093ea1f05928b123dae38b710631362bef1601 Mon Sep 17 00:00:00 2001 From: Keith Busch Date: Tue, 22 Oct 2024 15:48:47 -0700 Subject: PCI: Make pci_stop_dev() concurrent safe Use the atomic ADDED flag to ensure concurrent callers can't attempt to stop the device multiple times. Callers should currently all be holding the pci_rescan_remove_lock, so there shouldn't be an existing race. But that global lock can cause lock dependency issues, so this is preparing to reduce reliance on that lock by using the existing existing atomic bit ops. Link: https://lore.kernel.org/r/20241022224851.340648-2-kbusch@meta.com Signed-off-by: Keith Busch [bhelgaas: squash https://lore.kernel.org/r/20241111180659.3321671-1-kbusch@meta.com] Signed-off-by: Bjorn Helgaas Reviewed-by: Jonathan Cameron --- drivers/pci/bus.c | 2 +- drivers/pci/pci.h | 11 +++++++++-- drivers/pci/remove.c | 19 +++++++++---------- 3 files changed, 19 insertions(+), 13 deletions(-) diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c index 55c853686051..e41dfece0d96 100644 --- a/drivers/pci/bus.c +++ b/drivers/pci/bus.c @@ -348,7 +348,7 @@ void pci_bus_add_device(struct pci_dev *dev) if (retval < 0 && retval != -EPROBE_DEFER) pci_warn(dev, "device attach failed (%d)\n", retval); - pci_dev_assign_added(dev, true); + pci_dev_assign_added(dev); if (dev_of_node(&dev->dev) && pci_is_bridge(dev)) { retval = of_platform_populate(dev_of_node(&dev->dev), NULL, NULL, diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index 14d00ce45bfa..0d9169e0e7d2 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -470,9 +470,16 @@ static inline int pci_dev_set_disconnected(struct pci_dev *dev, void *unused) #define PCI_DPC_RECOVERED 1 #define PCI_DPC_RECOVERING 2 -static inline void pci_dev_assign_added(struct pci_dev *dev, bool added) +static inline void pci_dev_assign_added(struct pci_dev *dev) { - assign_bit(PCI_DEV_ADDED, &dev->priv_flags, added); + smp_mb__before_atomic(); + set_bit(PCI_DEV_ADDED, &dev->priv_flags); + smp_mb__after_atomic(); +} + +static inline bool pci_dev_test_and_clear_added(struct pci_dev *dev) +{ + return test_and_clear_bit(PCI_DEV_ADDED, &dev->priv_flags); } static inline bool pci_dev_is_added(const struct pci_dev *dev) diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c index e4ce1145aa3e..78863f241a88 100644 --- a/drivers/pci/remove.c +++ b/drivers/pci/remove.c @@ -33,16 +33,15 @@ static void pci_stop_dev(struct pci_dev *dev) { pci_pme_active(dev, false); - if (pci_dev_is_added(dev)) { - device_for_each_child(dev->dev.parent, dev_of_node(&dev->dev), - pci_pwrctl_unregister); - device_release_driver(&dev->dev); - pci_proc_detach_device(dev); - pci_remove_sysfs_dev_files(dev); - of_pci_remove_node(dev); - - pci_dev_assign_added(dev, false); - } + if (!pci_dev_test_and_clear_added(dev)) + return; + + device_for_each_child(dev->dev.parent, dev_of_node(&dev->dev), + pci_pwrctl_unregister); + device_release_driver(&dev->dev); + pci_proc_detach_device(dev); + pci_remove_sysfs_dev_files(dev); + of_pci_remove_node(dev); } static void pci_destroy_dev(struct pci_dev *dev) -- cgit v1.2.3 From e3f30d563a388220a7c4e3b9a7b52ac0b0324b26 Mon Sep 17 00:00:00 2001 From: Keith Busch Date: Tue, 22 Oct 2024 15:48:48 -0700 Subject: PCI: Make pci_destroy_dev() concurrent safe Use an atomic flag instead of the racy check against the device's kobj parent. We shouldn't be poking into device implementation details at this level anyway. Link: https://lore.kernel.org/r/20241022224851.340648-3-kbusch@meta.com Signed-off-by: Keith Busch Signed-off-by: Bjorn Helgaas Reviewed-by: Jonathan Cameron --- drivers/pci/pci.h | 6 ++++++ drivers/pci/remove.c | 2 +- 2 files changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index 0d9169e0e7d2..187c5c83412d 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -469,6 +469,7 @@ static inline int pci_dev_set_disconnected(struct pci_dev *dev, void *unused) #define PCI_DEV_ADDED 0 #define PCI_DPC_RECOVERED 1 #define PCI_DPC_RECOVERING 2 +#define PCI_DEV_REMOVED 3 static inline void pci_dev_assign_added(struct pci_dev *dev) { @@ -487,6 +488,11 @@ static inline bool pci_dev_is_added(const struct pci_dev *dev) return test_bit(PCI_DEV_ADDED, &dev->priv_flags); } +static inline bool pci_dev_test_and_set_removed(struct pci_dev *dev) +{ + return test_and_set_bit(PCI_DEV_REMOVED, &dev->priv_flags); +} + #ifdef CONFIG_PCIEAER #include diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c index 78863f241a88..1f35945459fd 100644 --- a/drivers/pci/remove.c +++ b/drivers/pci/remove.c @@ -46,7 +46,7 @@ static void pci_stop_dev(struct pci_dev *dev) static void pci_destroy_dev(struct pci_dev *dev) { - if (!dev->dev.kobj.parent) + if (pci_dev_test_and_set_removed(dev)) return; pci_npem_remove(dev); -- cgit v1.2.3 From 4d6dcd6c2fa3a80898651d323c150e5ebc03881d Mon Sep 17 00:00:00 2001 From: Keith Busch Date: Tue, 22 Oct 2024 15:48:49 -0700 Subject: PCI: Move __pci_walk_bus() mutex to where we need it MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Simplify __pci_walk_bus() by moving the pci_bus_sem mutex into pci_walk_bus(), the only place it is needed, and removing the parameter that told __pci_walk_bus() whether to acquire the mutex. Link: https://lore.kernel.org/r/20241022224851.340648-4-kbusch@meta.com Signed-off-by: Keith Busch [bhelgaas: commit log] Signed-off-by: Bjorn Helgaas Reviewed-by: Jonathan Cameron Reviewed-by: Davidlohr Bueso Reviewed-by: Ilpo Järvinen --- drivers/pci/bus.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c index e41dfece0d96..7c07a141e877 100644 --- a/drivers/pci/bus.c +++ b/drivers/pci/bus.c @@ -390,7 +390,7 @@ void pci_bus_add_devices(const struct pci_bus *bus) EXPORT_SYMBOL(pci_bus_add_devices); static void __pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *), - void *userdata, bool locked) + void *userdata) { struct pci_dev *dev; struct pci_bus *bus; @@ -398,8 +398,6 @@ static void __pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void int retval; bus = top; - if (!locked) - down_read(&pci_bus_sem); next = top->devices.next; for (;;) { if (next == &bus->devices) { @@ -422,8 +420,6 @@ static void __pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void if (retval) break; } - if (!locked) - up_read(&pci_bus_sem); } /** @@ -441,7 +437,9 @@ static void __pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void */ void pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *), void *userdata) { - __pci_walk_bus(top, cb, userdata, false); + down_read(&pci_bus_sem); + __pci_walk_bus(top, cb, userdata); + up_read(&pci_bus_sem); } EXPORT_SYMBOL_GPL(pci_walk_bus); @@ -449,7 +447,7 @@ void pci_walk_bus_locked(struct pci_bus *top, int (*cb)(struct pci_dev *, void * { lockdep_assert_held(&pci_bus_sem); - __pci_walk_bus(top, cb, userdata, true); + __pci_walk_bus(top, cb, userdata); } EXPORT_SYMBOL_GPL(pci_walk_bus_locked); -- cgit v1.2.3 From ee061da777f704976c6d3fdc1707788d11a052c5 Mon Sep 17 00:00:00 2001 From: Keith Busch Date: Tue, 22 Oct 2024 15:48:50 -0700 Subject: PCI: Convert __pci_walk_bus() to be recursive MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The original implementation of __pci_walk_bus() chose a non-recursive walk, presumably as a precaution on stack use. We do recursive bus walking in other places though. For example: pci_bus_resettable() pci_stop_bus_device() pci_remove_bus_device() pci_bus_allocate_dev_resources() So recursive pci bus walking is well tested and safe, and is easier to follow. Convert __pci_walk_bus() to be recursive to make it easier to introduce finer grain locking in the future. Link: https://lore.kernel.org/r/20241022224851.340648-5-kbusch@meta.com Signed-off-by: Keith Busch [bhelgaas: commit log] Signed-off-by: Bjorn Helgaas Reviewed-by: Jonathan Cameron Reviewed-by: Ilpo Järvinen --- drivers/pci/bus.c | 36 +++++++++++------------------------- 1 file changed, 11 insertions(+), 25 deletions(-) diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c index 7c07a141e877..8491e9c7f058 100644 --- a/drivers/pci/bus.c +++ b/drivers/pci/bus.c @@ -389,37 +389,23 @@ void pci_bus_add_devices(const struct pci_bus *bus) } EXPORT_SYMBOL(pci_bus_add_devices); -static void __pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *), - void *userdata) +static int __pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *), + void *userdata) { struct pci_dev *dev; - struct pci_bus *bus; - struct list_head *next; - int retval; + int ret = 0; - bus = top; - next = top->devices.next; - for (;;) { - if (next == &bus->devices) { - /* end of this bus, go up or finish */ - if (bus == top) + list_for_each_entry(dev, &top->devices, bus_list) { + ret = cb(dev, userdata); + if (ret) + break; + if (dev->subordinate) { + ret = __pci_walk_bus(dev->subordinate, cb, userdata); + if (ret) break; - next = bus->self->bus_list.next; - bus = bus->self->bus; - continue; } - dev = list_entry(next, struct pci_dev, bus_list); - if (dev->subordinate) { - /* this is a pci-pci bridge, do its devices next */ - next = dev->subordinate->devices.next; - bus = dev->subordinate; - } else - next = dev->bus_list.next; - - retval = cb(dev, userdata); - if (retval) - break; } + return ret; } /** -- cgit v1.2.3 From 38a18dfe9035d5a02a53271824de1854129c61dc Mon Sep 17 00:00:00 2001 From: Keith Busch Date: Tue, 22 Oct 2024 15:48:51 -0700 Subject: PCI: Unexport pci_walk_bus_locked() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit There's only one user of pci_walk_bus_locked(), and it's internal to the PCI core. Unexport it and make it private to drivers/pci/. Link: https://lore.kernel.org/r/20241022224851.340648-6-kbusch@meta.com Signed-off-by: Keith Busch [bhelgaas: move decl to drivers/pci/pci.h] Signed-off-by: Bjorn Helgaas Reviewed-by: Jonathan Cameron Reviewed-by: Davidlohr Bueso Reviewed-by: Ilpo Järvinen --- drivers/pci/bus.c | 1 - drivers/pci/pci.h | 3 +++ include/linux/pci.h | 2 -- 3 files changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c index 8491e9c7f058..30620f3bb0e2 100644 --- a/drivers/pci/bus.c +++ b/drivers/pci/bus.c @@ -435,7 +435,6 @@ void pci_walk_bus_locked(struct pci_bus *top, int (*cb)(struct pci_dev *, void * __pci_walk_bus(top, cb, userdata); } -EXPORT_SYMBOL_GPL(pci_walk_bus_locked); struct pci_bus *pci_bus_get(struct pci_bus *bus) { diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index 187c5c83412d..28cccfeb8076 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -323,6 +323,9 @@ void __pci_bus_assign_resources(const struct pci_bus *bus, struct list_head *realloc_head, struct list_head *fail_head); bool pci_bus_clip_resource(struct pci_dev *dev, int idx); +void pci_walk_bus_locked(struct pci_bus *top, + int (*cb)(struct pci_dev *, void *), + void *userdata); const char *pci_resource_name(struct pci_dev *dev, unsigned int i); diff --git a/include/linux/pci.h b/include/linux/pci.h index 573b4c4c2be6..056290377273 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -1623,8 +1623,6 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max, void pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *), void *userdata); -void pci_walk_bus_locked(struct pci_bus *top, int (*cb)(struct pci_dev *, void *), - void *userdata); int pci_cfg_space_size(struct pci_dev *dev); unsigned char pci_bus_max_busnr(struct pci_bus *bus); void pci_setup_bridge(struct pci_bus *bus); -- cgit v1.2.3