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/media/mc/mc-devnode.c | 326 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 326 insertions(+) create mode 100644 drivers/media/mc/mc-devnode.c (limited to 'drivers/media/mc/mc-devnode.c') diff --git a/drivers/media/mc/mc-devnode.c b/drivers/media/mc/mc-devnode.c new file mode 100644 index 000000000..51260a7d6 --- /dev/null +++ b/drivers/media/mc/mc-devnode.c @@ -0,0 +1,326 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Media device node + * + * Copyright (C) 2010 Nokia Corporation + * + * Based on drivers/media/video/v4l2_dev.c code authored by + * Mauro Carvalho Chehab (version 2) + * Alan Cox, (version 1) + * + * Contacts: Laurent Pinchart + * Sakari Ailus + * + * -- + * + * Generic media device node infrastructure to register and unregister + * character devices using a dynamic major number and proper reference + * counting. + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include + +#define MEDIA_NUM_DEVICES 256 +#define MEDIA_NAME "media" + +static dev_t media_dev_t; + +/* + * Active devices + */ +static DEFINE_MUTEX(media_devnode_lock); +static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES); + +/* debugfs */ +struct dentry *media_debugfs_root; + +/* Called when the last user of the media device exits. */ +static void media_devnode_release(struct device *cd) +{ + struct media_devnode *devnode = to_media_devnode(cd); + + /* Release media_devnode and perform other cleanups as needed. */ + if (devnode->release) + devnode->release(devnode); + + kfree(devnode); + pr_debug("%s: Media Devnode Deallocated\n", __func__); +} + +static const struct bus_type media_bus_type = { + .name = MEDIA_NAME, +}; + +static ssize_t media_read(struct file *filp, char __user *buf, + size_t sz, loff_t *off) +{ + struct media_devnode *devnode = media_devnode_data(filp); + + if (!devnode->fops->read) + return -EINVAL; + if (!media_devnode_is_registered(devnode)) + return -EIO; + return devnode->fops->read(filp, buf, sz, off); +} + +static ssize_t media_write(struct file *filp, const char __user *buf, + size_t sz, loff_t *off) +{ + struct media_devnode *devnode = media_devnode_data(filp); + + if (!devnode->fops->write) + return -EINVAL; + if (!media_devnode_is_registered(devnode)) + return -EIO; + return devnode->fops->write(filp, buf, sz, off); +} + +static __poll_t media_poll(struct file *filp, + struct poll_table_struct *poll) +{ + struct media_devnode *devnode = media_devnode_data(filp); + + if (!media_devnode_is_registered(devnode)) + return EPOLLERR | EPOLLHUP; + if (!devnode->fops->poll) + return DEFAULT_POLLMASK; + return devnode->fops->poll(filp, poll); +} + +static long +__media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg, + long (*ioctl_func)(struct file *filp, unsigned int cmd, + unsigned long arg)) +{ + struct media_devnode *devnode = media_devnode_data(filp); + + if (!ioctl_func) + return -ENOTTY; + + if (!media_devnode_is_registered(devnode)) + return -EIO; + + return ioctl_func(filp, cmd, arg); +} + +static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) +{ + struct media_devnode *devnode = media_devnode_data(filp); + + return __media_ioctl(filp, cmd, arg, devnode->fops->ioctl); +} + +#ifdef CONFIG_COMPAT + +static long media_compat_ioctl(struct file *filp, unsigned int cmd, + unsigned long arg) +{ + struct media_devnode *devnode = media_devnode_data(filp); + + return __media_ioctl(filp, cmd, arg, devnode->fops->compat_ioctl); +} + +#endif /* CONFIG_COMPAT */ + +/* Override for the open function */ +static int media_open(struct inode *inode, struct file *filp) +{ + struct media_devnode *devnode; + int ret; + + /* Check if the media device is available. This needs to be done with + * the media_devnode_lock held to prevent an open/unregister race: + * without the lock, the device could be unregistered and freed between + * the media_devnode_is_registered() and get_device() calls, leading to + * a crash. + */ + mutex_lock(&media_devnode_lock); + devnode = container_of(inode->i_cdev, struct media_devnode, cdev); + /* return ENXIO if the media device has been removed + already or if it is not registered anymore. */ + if (!media_devnode_is_registered(devnode)) { + mutex_unlock(&media_devnode_lock); + return -ENXIO; + } + /* and increase the device refcount */ + get_device(&devnode->dev); + mutex_unlock(&media_devnode_lock); + + filp->private_data = devnode; + + if (devnode->fops->open) { + ret = devnode->fops->open(filp); + if (ret) { + put_device(&devnode->dev); + filp->private_data = NULL; + return ret; + } + } + + return 0; +} + +/* Override for the release function */ +static int media_release(struct inode *inode, struct file *filp) +{ + struct media_devnode *devnode = media_devnode_data(filp); + + if (devnode->fops->release) + devnode->fops->release(filp); + + filp->private_data = NULL; + + /* decrease the refcount unconditionally since the release() + return value is ignored. */ + put_device(&devnode->dev); + + return 0; +} + +static const struct file_operations media_devnode_fops = { + .owner = THIS_MODULE, + .read = media_read, + .write = media_write, + .open = media_open, + .unlocked_ioctl = media_ioctl, +#ifdef CONFIG_COMPAT + .compat_ioctl = media_compat_ioctl, +#endif /* CONFIG_COMPAT */ + .release = media_release, + .poll = media_poll, +}; + +int __must_check media_devnode_register(struct media_device *mdev, + struct media_devnode *devnode, + struct module *owner) +{ + int minor; + int ret; + + /* Part 1: Find a free minor number */ + mutex_lock(&media_devnode_lock); + minor = find_first_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES); + if (minor == MEDIA_NUM_DEVICES) { + mutex_unlock(&media_devnode_lock); + pr_err("could not get a free minor\n"); + kfree(devnode); + return -ENFILE; + } + + set_bit(minor, media_devnode_nums); + mutex_unlock(&media_devnode_lock); + + devnode->minor = minor; + devnode->media_dev = mdev; + + /* Part 1: Initialize dev now to use dev.kobj for cdev.kobj.parent */ + devnode->dev.bus = &media_bus_type; + devnode->dev.devt = MKDEV(MAJOR(media_dev_t), devnode->minor); + devnode->dev.release = media_devnode_release; + if (devnode->parent) + devnode->dev.parent = devnode->parent; + dev_set_name(&devnode->dev, "media%d", devnode->minor); + dev_set_drvdata(&devnode->dev, mdev); + device_initialize(&devnode->dev); + + /* Part 2: Initialize the character device */ + cdev_init(&devnode->cdev, &media_devnode_fops); + devnode->cdev.owner = owner; + kobject_set_name(&devnode->cdev.kobj, "media%d", devnode->minor); + + /* Part 3: Add the media and char device */ + set_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); + ret = cdev_device_add(&devnode->cdev, &devnode->dev); + if (ret < 0) { + clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); + pr_err("%s: cdev_device_add failed\n", __func__); + goto cdev_add_error; + } + + return 0; + +cdev_add_error: + mutex_lock(&media_devnode_lock); + clear_bit(devnode->minor, media_devnode_nums); + devnode->media_dev = NULL; + mutex_unlock(&media_devnode_lock); + + put_device(&devnode->dev); + return ret; +} + +void media_devnode_unregister_prepare(struct media_devnode *devnode) +{ + /* Check if devnode was ever registered at all */ + if (!media_devnode_is_registered(devnode)) + return; + + mutex_lock(&media_devnode_lock); + clear_bit(MEDIA_FLAG_REGISTERED, &devnode->flags); + mutex_unlock(&media_devnode_lock); +} + +void media_devnode_unregister(struct media_devnode *devnode) +{ + mutex_lock(&media_devnode_lock); + /* Delete the cdev on this minor as well */ + cdev_device_del(&devnode->cdev, &devnode->dev); + devnode->media_dev = NULL; + clear_bit(devnode->minor, media_devnode_nums); + mutex_unlock(&media_devnode_lock); + + put_device(&devnode->dev); +} + +/* + * Initialise media for linux + */ +static int __init media_devnode_init(void) +{ + int ret; + + pr_info("Linux media interface: v0.10\n"); + ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES, + MEDIA_NAME); + if (ret < 0) { + pr_warn("unable to allocate major\n"); + return ret; + } + + ret = bus_register(&media_bus_type); + if (ret < 0) { + unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES); + pr_warn("bus_register failed\n"); + return -EIO; + } + + return 0; +} + +static void __exit media_devnode_exit(void) +{ + debugfs_remove_recursive(media_debugfs_root); + bus_unregister(&media_bus_type); + unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES); +} + +subsys_initcall(media_devnode_init); +module_exit(media_devnode_exit) + +MODULE_AUTHOR("Laurent Pinchart "); +MODULE_DESCRIPTION("Device node registration for media drivers"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1