Merge tag 'linux-can-next-for-3.19-20141207' of git://gitorious.org/linux-can/linux-can-next

Marc Kleine-Budde says:

====================
pull-request: can-next 2014-12-07

this is a pull request of 8 patches for net-next/master.

Andri Yngvason contributes 4 patches in which the CAN state change
handling is consolidated and unified among the sja1000, mscan and
flexcan driver. The three patches by Jeremiah Mahler fix spelling
mistakes and eliminate the banner[] variable in various parts. And a
patch by me that switches on sparse endianess checking by default.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

0 files changed, 0 insertions, 0 deletions

path: root/include/uapi/linux/kernelcapi.h

/*
 * Generic pidhash and scalable, time-bounded PID allocator
 *
 * (C) 2002-2003 Nadia Yvette Chambers, IBM
 * (C) 2004 Nadia Yvette Chambers, Oracle
 * (C) 2002-2004 Ingo Molnar, Red Hat
 *
 * pid-structures are backing objects for tasks sharing a given ID to chain
 * against. There is very little to them aside from hashing them and
 * parking tasks using given ID's on a list.
 *
 * The hash is always changed with the tasklist_lock write-acquired,
 * and the hash is only accessed with the tasklist_lock at least
 * read-acquired, so there's no additional SMP locking needed here.
 *
 * We have a list of bitmap pages, which bitmaps represent the PID space.
 * Allocating and freeing PIDs is completely lockless. The worst-case
 * allocation scenario when all but one out of 1 million PIDs possible are
 * allocated already: the scanning of 32 list entries and at most PAGE_SIZE
 * bytes. The typical fastpath is a single successful setbit. Freeing is O(1).
 *
 * Pid namespaces:
 *    (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
 *    (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
 *     Many thanks to Oleg Nesterov for comments and help
 *
 */

#include <linux/mm.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/rculist.h>
#include <linux/bootmem.h>
#include <linux/hash.h>
#include <linux/pid_namespace.h>
#include <linux/init_task.h>
#include <linux/syscalls.h>
#include <linux/proc_ns.h>
#include <linux/proc_fs.h>

#define pid_hashfn(nr, ns)	\
	hash_long((unsigned long)nr + (unsigned long)ns, pidhash_shift)
static struct hlist_head *pid_hash;
static unsigned int pidhash_shift = 4;
struct pid init_struct_pid = INIT_STRUCT_PID;

int pid_max = PID_MAX_DEFAULT;

#define RESERVED_PIDS		300

int pid_max_min = RESERVED_PIDS + 1;
int pid_max_max = PID_MAX_LIMIT;

static inline int mk_pid(struct pid_namespace *pid_ns,
		struct pidmap *map, int off)
{
	return (map - pid_ns->pidmap)*BITS_PER_PAGE + off;
}

#define find_next_offset(map, off)					\
		find_next_zero_bit((map)->page, BITS_PER_PAGE, off)

/*
 * PID-map pages start out as NULL, they get allocated upon
 * first use and are never deallocated. This way a low pid_max
 * value does not cause lots of bitmaps to be allocated, but
 * the scheme scales to up to 4 million PIDs, runtime.
 */
struct pid_namespace init_pid_ns = {
	.kref = {
		.refcount       = ATOMIC_INIT(2),
	},
	.pidmap = {
		[ 0 ... PIDMAP_ENTRIES-1] = { ATOMIC_INIT(BITS_PER_PAGE), NULL }
	},
	.last_pid = 0,
	.nr_hashed = PIDNS_HASH_ADDING,
	.level = 0,
	.child_reaper = &init_task,
	.user_ns = &init_user_ns,
	.ns.inum = PROC_PID_INIT_INO,
#ifdef CONFIG_PID_NS
	.ns.ops = &pidns_operations,
#endif
};
EXPORT_SYMBOL_GPL(init_pid_ns);

/*
 * Note: disable interrupts while the pidmap_lock is held as an
 * interrupt might come in and do read_lock(&tasklist_lock).
 *
 * If we don't disable interrupts there is a nasty deadlock between
 * detach_pid()->free_pid() and another cpu that does
 * spin_lock(&pidmap_lock) followed by an interrupt routine that does
 * read_lock(&tasklist_lock);
 *
 * After we clean up the tasklist_lock and know there are no
 * irq handlers that take it we can leave the interrupts enabled.
 * For now it is easier to be safe than to prove it can't happen.
 */

static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(pidmap_lock);

static void free_pidmap(struct upid *upid)
{
	int nr = upid->nr;
	struct pidmap *map = upid->ns->pidmap + nr / BITS_PER_PAGE;
	int offset = nr & BITS_PER_PAGE_MASK;

	clear_bit(offset, map->page);
	atomic_inc(&map->nr_free);
}

/*
 * If we started walking pids at 'base', is 'a' seen before 'b'?
 */
static int pid_before(int base, int a, int b)
{
	/*
	 * This is the same as saying
	 *
	 * (a - base + MAXUINT) % MAXUINT < (b - base + MAXUINT) % MAXUINT
	 * and that mapping orders 'a' and 'b' with respect to 'base'.
	 */
	return (unsigned)(a - base) < (unsigned)(b - base);
}

/*
 * We might be racing with someone else trying to set pid_ns->last_pid
 * at the pid allocation time (there's also a sysctl for this, but racing
 * with this one is OK, see comment in kernel/pid_namespace.c about it).
 * We want the winner to have the "later" value, because if the
 * "earlier" value prevails, then a pid may get reused immediately.
 *
 * Since pids rollover, it is not sufficient to just pick the bigger
 * value.  We have to consider where we started counting from.
 *
 * 'base' is the value of pid_ns->last_pid that we observed when
 * we started looking for a pid.
 *
 * 'pid' is the pid that we eventually found.
 */
static void set_last_pid(struct pid_namespace *pid_ns, int base, int pid)
{
	int prev;
	int last_write = base;
	do {
		prev = last_write;
		last_write = cmpxchg(&pid_ns->last_pid, prev, pid);
	} while ((prev != last_write) && (pid_before(base, last_write, pid)));
}

static int alloc_pidmap(struct pid_namespace *pid_ns)
{
	int i, offset, max_scan, pid, last = pid_ns->last_pid;
	struct pidmap *map;

	pid = last + 1;
	if (pid >= pid_max)
		pid = RESERVED_PIDS;
	offset = pid & BITS_PER_PAGE_MASK;
	map = &pid_ns->pidmap[pid/BITS_PER_PAGE];
	/*
	 * If last_pid points into the middle of the map->page we
	 * want to scan this bitmap block twice, the second time
	 * we start with offset == 0 (or RESERVED_PIDS).
	 */
	max_scan = DIV_ROUND_UP(pid_max, BITS_PER_PAGE) - !offset;
	for (i = 0; i <= max_scan; ++i) {
		if (unlikely(!map->page)) {
			void *page = kzalloc(PAGE_SIZE, GFP_KERNEL);
			/*
			 * Free the page if someone raced with us
			 * installing it:
			 */
			spin_lock_irq(&pidmap_lock);
			if (!map->page) {
				map->page = page;
				page = NULL;
			}
			spin_unlock_irq(&pidmap_lock);
			kfree(page);
			if (unlikely(!map->page))
				break;
		}
		if (likely(atomic_read(&map->nr_free))) {
			for ( ; ; ) {
				if (!test_and_set_bit(offset, map->page)) {
					atomic_dec(&map->nr_free);
					set_last_pid(pid_ns, last, pid);
					return pid;
				}
				offset = find_next_offset(map, offset);
				if (offset >= BITS_PER_PAGE)
					break;
				pid = mk_pid(pid_ns, map, offset);
				if (pid >= pid_max)
					break;
			}
		}
		if (map < &pid_ns->pidmap[(pid_max-1)/BITS_PER_PAGE]) {
			++map;
			offset = 0;
		} else {
			map = &pid_ns->pidmap[0];
			offset = RESERVED_PIDS;
			if (unlikely(last == offset))
				break;
		}
		pid = mk_pid(pid_ns, map, offset);
	}
	return -1;
}

int next_pidmap(struct pid_namespace *pid_ns, unsigned int last)
{
	int offset;
	struct pidmap *map, *end;

	if (last >= PID_MAX_LIMIT)
		return -1;

	offset = (last + 1) & BITS_PER_PAGE_MASK;
	map = &pid_ns->pidmap[(last + 1)/BITS_PER_PAGE];
	end = &pid_ns->pidmap[PIDMAP_ENTRIES];
	for (; map < end; map++, offset = 0) {
		if (unlikely(!map->page))
			continue;
		offset = find_next_bit((map)->page, BITS_PER_PAGE, offset);
		if (offset < BITS_PER_PAGE)
			return mk_pid(pid_ns, map, offset);
	}
	return -1;
}

void put_pid(struct pid *pid)
{
	struct pid_namespace *ns;

	if (!pid)
		return;

	ns = pid->numbers[pid->level].ns;
	if ((atomic_read(&pid->count) == 1) ||
	     atomic_dec_and_test(&pid->count)) {
		kmem_cache_free(ns->pid_cachep, pid);
		put_pid_ns(ns);
	}
}
EXPORT_SYMBOL_GPL(put_pid);

static void delayed_put_pid(struct rcu_head *rhp)
{
	struct pid *pid = container_of(rhp, struct pid, rcu);
	put_pid(pid);
}

void free_pid(struct pid *pid)
{
	/* We can be called with write_lock_irq(&tasklist_lock) held */
	int i;
	unsigned long flags;

	spin_lock_irqsave(&pidmap_lock, flags);
	for (i = 0; i <= pid->level; i++) {
		struct upid *upid = pid->numbers + i;
		struct pid_namespace *ns = upid->ns;
		hlist_del_rcu(&upid->pid_chain);
		switch(--ns->nr_hashed) {
		case 2:
		case 1:
			/* When all that is left in the pid namespace
			 * is the reaper wake up the reaper.  The reaper
			 * may be sleeping in zap_pid_ns_processes().
			 */
			wake_up_process(ns->child_reaper);
			break;
		case PIDNS_HASH_ADDING:
			/* Handle a fork failure of the first process */
			WARN_ON(ns->child_reaper);
			ns->nr_hashed = 0;
			/* fall through */
		case 0:
			schedule_work(&ns->proc_work);
			break;
		}
	}
	spin_unlock_irqrestore(&pidmap_lock, flags);

	for (i = 0; i <= pid->level; i++)
		free_pidmap(pid->numbers + i);

	call_rcu(&pid->rcu, delayed_put_pid);
}

struct pid *alloc_pid(struct pid_namespace *ns)
{
	struct pid *pid;
	enum pid_type type;
	int i, nr;
	struct pid_namespace *tmp;
	struct upid *upid;

	pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL);
	if (!pid)
		goto out;

	tmp = ns;
	pid->level = ns->level;
	for (i = ns->level; i >= 0; i--) {
		nr = alloc_pidmap(tmp);
		if (nr < 0)
			goto out_free;

		pid->numbers[i].nr = nr;
		pid->numbers[i].ns = tmp;
		tmp = tmp->parent;
	}

	if (unlikely(is_child_reaper(pid))) {
		if (pid_ns_prepare_proc(ns))
			goto out_free;
	}

	get_pid_ns(ns);
	atomic_set(&pid->count, 1);
	for (type = 0; type < PIDTYPE_MAX; ++type)
		INIT_HLIST_HEAD(&pid->tasks[type]);

	upid = pid->numbers + ns->level;
	spin_lock_irq(&pidmap_lock);
	if (!(ns->nr_hashed & PIDNS_HASH_ADDING))
		goto out_unlock;
	for ( ; upid >= pid->numbers; --upid) {
		hlist_add_head_rcu(&upid->pid_chain,
				&pid_hash[pid_hashfn(upid->nr, upid->ns)]);
		upid->ns->nr_hashed++;
	}
	spin_unlock_irq(&pidmap_lock);

out:
	return pid;

out_unlock:
	spin_unlock_irq(&pidmap_lock);
	put_pid_ns(ns);

out_free:
	while (++i <= ns->level)
		free_pidmap(pid->numbers + i);

	kmem_cache_free(ns->pid_cachep, pid);
	pid = NULL;
	goto out;
}

void disable_pid_allocation(struct pid_namespace *ns)
{
	spin_lock_irq(&pidmap_lock);
	ns->nr_hashed &= ~PIDNS_HASH_ADDING;
	spin_unlock_irq(&pidmap_lock);
}

struct pid *find_pid_ns(int nr, struct pid_namespace *ns)
{
	struct upid *pnr;

	hlist_for_each_entry_rcu(pnr,
			&pid_hash[pid_hashfn(nr, ns)], pid_chain)
		if (pnr->nr == nr && pnr->ns == ns)
			return container_of(pnr, struct pid,
					numbers[ns->level]);

	return NULL;
}
EXPORT_SYMBOL_GPL(find_pid_ns);

struct pid *find_vpid(int nr)
{
	return find_pid_ns(nr, task_active_pid_ns(current));
}
EXPORT_SYMBOL_GPL(find_vpid);

/*
 * attach_pid() must be called with the tasklist_lock write-held.
 */
void attach_pid(struct task_struct *task, enum pid_type type)
{
	struct pid_link *link = &task->pids[type];
	hlist_add_head_rcu(&link->node, &link->pid->tasks[type]);
}

static void __change_pid(struct task_struct *task, enum pid_type type,
			struct pid *new)
{
	struct pid_link *link;
	struct pid *pid;
	int tmp;