From a9e3760b0838299649c0d57cca44daaf40ba3c33 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 14 Sep 2026 22:12:34 -1000 Subject: sched_ext: Maintain an online cid mask in the scheduler arena Schedulers on the default cid mapping treat [0, nr_online_cids) as the online set and restart on hotplug. Schedulers that install their own mapping with scx_bpf_cid_override() have no way to learn which cids are online: the count no longer identifies members and the CPU-form cpumask is unusable from cid programs. This is an obvious hole in the cid API. Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's arena, allocated alongside the per-CPU scratch masks and populated after the cid mapping is finalized and before ops.init(), for child schedulers too. The pointer stays valid through ops.exit() with no reference to take. It is the arena offset as a void pointer, the same form struct_ops arena arguments arrive in. The verifier types the void return as a scalar for the program's arena cast. The mask follows the SCX hotplug notifications: seeded from cpu_active_mask and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask only inside a hotplug transition. Updates walk the scheduler list under the lock that also serializes unlinking. Reads are live, not atomic snapshots. Root initialization excludes hotplug. v2: Reworded the getter kerneldoc (Andrea Righi). Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi --- drivers/base/driver.c | 204 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 204 insertions(+) create mode 100644 drivers/base/driver.c (limited to 'drivers/base/driver.c') diff --git a/drivers/base/driver.c b/drivers/base/driver.c new file mode 100644 index 000000000..5d9c39081 --- /dev/null +++ b/drivers/base/driver.c @@ -0,0 +1,204 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * driver.c - centralized device driver management + * + * Copyright (c) 2002-3 Patrick Mochel + * Copyright (c) 2002-3 Open Source Development Labs + * Copyright (c) 2007 Greg Kroah-Hartman + * Copyright (c) 2007 Novell Inc. + */ + +#include +#include +#include +#include +#include +#include +#include +#include "base.h" + +static struct device *next_device(struct klist_iter *i) +{ + struct klist_node *n = klist_next(i); + struct device *dev = NULL; + struct device_private *dev_prv; + + if (n) { + dev_prv = to_device_private_driver(n); + dev = dev_prv->device; + } + return dev; +} + +/** + * driver_for_each_device - Iterator for devices bound to a driver. + * @drv: Driver we're iterating. + * @start: Device to begin with + * @data: Data to pass to the callback. + * @fn: Function to call for each device. + * + * Iterate over the @drv's list of devices calling @fn for each one. + */ +int driver_for_each_device(struct device_driver *drv, struct device *start, + void *data, device_iter_t fn) +{ + struct klist_iter i; + struct device *dev; + int error = 0; + + if (!drv) + return -EINVAL; + + klist_iter_init_node(&drv->p->klist_devices, &i, + start ? &start->p->knode_driver : NULL); + while (!error && (dev = next_device(&i))) + error = fn(dev, data); + klist_iter_exit(&i); + return error; +} +EXPORT_SYMBOL_GPL(driver_for_each_device); + +/** + * driver_find_device - device iterator for locating a particular device. + * @drv: The device's driver + * @start: Device to begin with + * @data: Data to pass to match function + * @match: Callback function to check device + * + * This is similar to the driver_for_each_device() function above, but + * it returns a reference to a device that is 'found' for later use, as + * determined by the @match callback. + * + * The callback should return 0 if the device doesn't match and non-zero + * if it does. If the callback returns non-zero, this function will + * return to the caller and not iterate over any more devices. + */ +struct device *driver_find_device(const struct device_driver *drv, + struct device *start, const void *data, + device_match_t match) +{ + struct klist_iter i; + struct device *dev; + + if (!drv || !drv->p) + return NULL; + + klist_iter_init_node(&drv->p->klist_devices, &i, + (start ? &start->p->knode_driver : NULL)); + while ((dev = next_device(&i))) { + if (match(dev, data)) { + get_device(dev); + break; + } + } + klist_iter_exit(&i); + return dev; +} +EXPORT_SYMBOL_GPL(driver_find_device); + +/** + * driver_create_file - create sysfs file for driver. + * @drv: driver. + * @attr: driver attribute descriptor. + */ +int driver_create_file(const struct device_driver *drv, + const struct driver_attribute *attr) +{ + int error; + + if (drv) + error = sysfs_create_file(&drv->p->kobj, &attr->attr); + else + error = -EINVAL; + return error; +} +EXPORT_SYMBOL_GPL(driver_create_file); + +/** + * driver_remove_file - remove sysfs file for driver. + * @drv: driver. + * @attr: driver attribute descriptor. + */ +void driver_remove_file(const struct device_driver *drv, + const struct driver_attribute *attr) +{ + if (drv) + sysfs_remove_file(&drv->p->kobj, &attr->attr); +} +EXPORT_SYMBOL_GPL(driver_remove_file); + +int driver_add_groups(const struct device_driver *drv, + const struct attribute_group *const *groups) +{ + return sysfs_create_groups(&drv->p->kobj, groups); +} + +void driver_remove_groups(const struct device_driver *drv, + const struct attribute_group *const *groups) +{ + sysfs_remove_groups(&drv->p->kobj, groups); +} + +/** + * driver_register - register driver with bus + * @drv: driver to register + * + * We pass off most of the work to the bus_add_driver() call, + * since most of the things we have to do deal with the bus + * structures. + */ +int driver_register(struct device_driver *drv) +{ + int ret; + struct device_driver *other; + + if (!bus_is_registered(drv->bus)) { + pr_err("Driver '%s' was unable to register with bus_type '%s' because the bus was not initialized.\n", + drv->name, drv->bus->name); + return -EINVAL; + } + + if ((drv->bus->probe && drv->probe) || + (drv->bus->remove && drv->remove) || + (drv->bus->shutdown && drv->shutdown)) + pr_warn("Driver '%s' needs updating - please use " + "bus_type methods\n", drv->name); + + other = driver_find(drv->name, drv->bus); + if (other) { + pr_err("Error: Driver '%s' is already registered, " + "aborting...\n", drv->name); + return -EBUSY; + } + + ret = bus_add_driver(drv); + if (ret) + return ret; + ret = driver_add_groups(drv, drv->groups); + if (ret) { + bus_remove_driver(drv); + return ret; + } + kobject_uevent(&drv->p->kobj, KOBJ_ADD); + deferred_probe_extend_timeout(); + + return ret; +} +EXPORT_SYMBOL_GPL(driver_register); + +/** + * driver_unregister - remove driver from system. + * @drv: driver. + * + * Again, we pass off most of the work to the bus-level call. + */ +void driver_unregister(struct device_driver *drv) +{ + if (!drv || !drv->p) { + WARN(1, "Unexpected driver unregister!\n"); + return; + } + driver_remove_groups(drv, drv->groups); + bus_remove_driver(drv); +} +EXPORT_SYMBOL_GPL(driver_unregister); -- cgit v1.3.1