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 --- samples/configfs/Makefile | 3 + samples/configfs/configfs_sample.c | 368 +++++++++++++++++++++++++++++++++++++ 2 files changed, 371 insertions(+) create mode 100644 samples/configfs/Makefile create mode 100644 samples/configfs/configfs_sample.c (limited to 'samples/configfs') diff --git a/samples/configfs/Makefile b/samples/configfs/Makefile new file mode 100644 index 000000000..92d661fcb --- /dev/null +++ b/samples/configfs/Makefile @@ -0,0 +1,3 @@ +# SPDX-License-Identifier: GPL-2.0-only + +obj-$(CONFIG_SAMPLE_CONFIGFS) += configfs_sample.o diff --git a/samples/configfs/configfs_sample.c b/samples/configfs/configfs_sample.c new file mode 100644 index 000000000..c1b108ec4 --- /dev/null +++ b/samples/configfs/configfs_sample.c @@ -0,0 +1,368 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * configfs_example_macros.c - This file is a demonstration module + * containing a number of configfs subsystems. It uses the helper + * macros defined by configfs.h + * + * Based on sysfs: + * sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel + * + * configfs Copyright (C) 2005 Oracle. All rights reserved. + */ + +#include +#include +#include +#include +#include + +/* + * 01-childless + * + * This first example is a childless subsystem. It cannot create + * any config_items. It just has attributes. + * + * Note that we are enclosing the configfs_subsystem inside a container. + * This is not necessary if a subsystem has no attributes directly + * on the subsystem. See the next example, 02-simple-children, for + * such a subsystem. + */ + +struct childless { + struct configfs_subsystem subsys; + int showme; + int storeme; +}; + +static inline struct childless *to_childless(struct config_item *item) +{ + return container_of(to_configfs_subsystem(to_config_group(item)), + struct childless, subsys); +} + +static ssize_t childless_showme_show(struct config_item *item, char *page) +{ + struct childless *childless = to_childless(item); + ssize_t pos; + + pos = sprintf(page, "%d\n", childless->showme); + childless->showme++; + + return pos; +} + +static ssize_t childless_storeme_show(struct config_item *item, char *page) +{ + return sprintf(page, "%d\n", to_childless(item)->storeme); +} + +static ssize_t childless_storeme_store(struct config_item *item, + const char *page, size_t count) +{ + struct childless *childless = to_childless(item); + int ret; + + ret = kstrtoint(page, 10, &childless->storeme); + if (ret) + return ret; + + return count; +} + +static ssize_t childless_description_show(struct config_item *item, char *page) +{ + return sprintf(page, +"[01-childless]\n" +"\n" +"The childless subsystem is the simplest possible subsystem in\n" +"configfs. It does not support the creation of child config_items.\n" +"It only has a few attributes. In fact, it isn't much different\n" +"than a directory in /proc.\n"); +} + +CONFIGFS_ATTR_RO(childless_, showme); +CONFIGFS_ATTR(childless_, storeme); +CONFIGFS_ATTR_RO(childless_, description); + +static struct configfs_attribute *childless_attrs[] = { + &childless_attr_showme, + &childless_attr_storeme, + &childless_attr_description, + NULL, +}; + +static const struct config_item_type childless_type = { + .ct_attrs = childless_attrs, + .ct_owner = THIS_MODULE, +}; + +static struct childless childless_subsys = { + .subsys = { + .su_group = { + .cg_item = { + .ci_namebuf = "01-childless", + .ci_type = &childless_type, + }, + }, + }, +}; + +/* ----------------------------------------------------------------- */ + +/* + * 02-simple-children + * + * This example merely has a simple one-attribute child. Note that + * there is no extra attribute structure, as the child's attribute is + * known from the get-go. Also, there is no container for the + * subsystem, as it has no attributes of its own. + */ + +struct simple_child { + struct config_item item; + int storeme; +}; + +static inline struct simple_child *to_simple_child(struct config_item *item) +{ + return container_of(item, struct simple_child, item); +} + +static ssize_t simple_child_storeme_show(struct config_item *item, char *page) +{ + return sprintf(page, "%d\n", to_simple_child(item)->storeme); +} + +static ssize_t simple_child_storeme_store(struct config_item *item, + const char *page, size_t count) +{ + struct simple_child *simple_child = to_simple_child(item); + int ret; + + ret = kstrtoint(page, 10, &simple_child->storeme); + if (ret) + return ret; + + return count; +} + +CONFIGFS_ATTR(simple_child_, storeme); + +static struct configfs_attribute *simple_child_attrs[] = { + &simple_child_attr_storeme, + NULL, +}; + +static void simple_child_release(struct config_item *item) +{ + kfree(to_simple_child(item)); +} + +static const struct configfs_item_operations simple_child_item_ops = { + .release = simple_child_release, +}; + +static const struct config_item_type simple_child_type = { + .ct_item_ops = &simple_child_item_ops, + .ct_attrs = simple_child_attrs, + .ct_owner = THIS_MODULE, +}; + +struct simple_children { + struct config_group group; +}; + +static inline struct simple_children *to_simple_children(struct config_item *item) +{ + return container_of(to_config_group(item), + struct simple_children, group); +} + +static struct config_item *simple_children_make_item(struct config_group *group, + const char *name) +{ + struct simple_child *simple_child; + + simple_child = kzalloc(sizeof(struct simple_child), GFP_KERNEL); + if (!simple_child) + return ERR_PTR(-ENOMEM); + + config_item_init_type_name(&simple_child->item, name, + &simple_child_type); + + return &simple_child->item; +} + +static ssize_t simple_children_description_show(struct config_item *item, + char *page) +{ + return sprintf(page, +"[02-simple-children]\n" +"\n" +"This subsystem allows the creation of child config_items. These\n" +"items have only one attribute that is readable and writeable.\n"); +} + +CONFIGFS_ATTR_RO(simple_children_, description); + +static struct configfs_attribute *simple_children_attrs[] = { + &simple_children_attr_description, + NULL, +}; + +static void simple_children_release(struct config_item *item) +{ + kfree(to_simple_children(item)); +} + +static const struct configfs_item_operations simple_children_item_ops = { + .release = simple_children_release, +}; + +/* + * Note that, since no extra work is required on ->drop_item(), + * no ->drop_item() is provided. + */ +static const struct configfs_group_operations simple_children_group_ops = { + .make_item = simple_children_make_item, +}; + +static const struct config_item_type simple_children_type = { + .ct_item_ops = &simple_children_item_ops, + .ct_group_ops = &simple_children_group_ops, + .ct_attrs = simple_children_attrs, + .ct_owner = THIS_MODULE, +}; + +static struct configfs_subsystem simple_children_subsys = { + .su_group = { + .cg_item = { + .ci_namebuf = "02-simple-children", + .ci_type = &simple_children_type, + }, + }, +}; + +/* ----------------------------------------------------------------- */ + +/* + * 03-group-children + * + * This example reuses the simple_children group from above. However, + * the simple_children group is not the subsystem itself, it is a + * child of the subsystem. Creation of a group in the subsystem creates + * a new simple_children group. That group can then have simple_child + * children of its own. + */ + +static struct config_group *group_children_make_group( + struct config_group *group, const char *name) +{ + struct simple_children *simple_children; + + simple_children = kzalloc(sizeof(struct simple_children), + GFP_KERNEL); + if (!simple_children) + return ERR_PTR(-ENOMEM); + + config_group_init_type_name(&simple_children->group, name, + &simple_children_type); + + return &simple_children->group; +} + +static ssize_t group_children_description_show(struct config_item *item, + char *page) +{ + return sprintf(page, +"[03-group-children]\n" +"\n" +"This subsystem allows the creation of child config_groups. These\n" +"groups are like the subsystem simple-children.\n"); +} + +CONFIGFS_ATTR_RO(group_children_, description); + +static struct configfs_attribute *group_children_attrs[] = { + &group_children_attr_description, + NULL, +}; + +/* + * Note that, since no extra work is required on ->drop_item(), + * no ->drop_item() is provided. + */ +static const struct configfs_group_operations group_children_group_ops = { + .make_group = group_children_make_group, +}; + +static const struct config_item_type group_children_type = { + .ct_group_ops = &group_children_group_ops, + .ct_attrs = group_children_attrs, + .ct_owner = THIS_MODULE, +}; + +static struct configfs_subsystem group_children_subsys = { + .su_group = { + .cg_item = { + .ci_namebuf = "03-group-children", + .ci_type = &group_children_type, + }, + }, +}; + +/* ----------------------------------------------------------------- */ + +/* + * We're now done with our subsystem definitions. + * For convenience in this module, here's a list of them all. It + * allows the init function to easily register them. Most modules + * will only have one subsystem, and will only call register_subsystem + * on it directly. + */ +static struct configfs_subsystem *example_subsys[] = { + &childless_subsys.subsys, + &simple_children_subsys, + &group_children_subsys, + NULL, +}; + +static int __init configfs_example_init(void) +{ + struct configfs_subsystem *subsys; + int ret, i; + + for (i = 0; example_subsys[i]; i++) { + subsys = example_subsys[i]; + + config_group_init(&subsys->su_group); + mutex_init(&subsys->su_mutex); + ret = configfs_register_subsystem(subsys); + if (ret) { + pr_err("Error %d while registering subsystem %s\n", + ret, subsys->su_group.cg_item.ci_namebuf); + goto out_unregister; + } + } + + return 0; + +out_unregister: + for (i--; i >= 0; i--) + configfs_unregister_subsystem(example_subsys[i]); + + return ret; +} + +static void __exit configfs_example_exit(void) +{ + int i; + + for (i = 0; example_subsys[i]; i++) + configfs_unregister_subsystem(example_subsys[i]); +} + +module_init(configfs_example_init); +module_exit(configfs_example_exit); +MODULE_DESCRIPTION("Sample configfs module"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1