#define pid_hashfn(nr, ns) \
hash_long((unsigned long)nr + (unsigned long)ns, pidhash_shift)
static struct hlist_head *pid_hash;
-static int pidhash_shift;
+static unsigned int pidhash_shift = 4;
struct pid init_struct_pid = INIT_STRUCT_PID;
int pid_max = PID_MAX_DEFAULT;
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.
+ * 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;
pid = RESERVED_PIDS;
offset = pid & BITS_PER_PAGE_MASK;
map = &pid_ns->pidmap[pid/BITS_PER_PAGE];
- max_scan = (pid_max + BITS_PER_PAGE - 1)/BITS_PER_PAGE - !offset;
+ /*
+ * 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);
* installing it:
*/
spin_lock_irq(&pidmap_lock);
- if (map->page)
- kfree(page);
- else
+ if (!map->page) {
map->page = page;
+ page = NULL;
+ }
spin_unlock_irq(&pidmap_lock);
+ kfree(page);
if (unlikely(!map->page))
break;
}
do {
if (!test_and_set_bit(offset, map->page)) {
atomic_dec(&map->nr_free);
- pid_ns->last_pid = pid;
+ set_last_pid(pid_ns, last, pid);
return pid;
}
offset = find_next_offset(map, offset);
pid = mk_pid(pid_ns, map, offset);
- /*
- * find_next_offset() found a bit, the pid from it
- * is in-bounds, and if we fell back to the last
- * bitmap block and the final block was the same
- * as the starting point, pid is before last_pid.
- */
- } while (offset < BITS_PER_PAGE && pid < pid_max &&
- (i != max_scan || pid < last ||
- !((last+1) & BITS_PER_PAGE_MASK)));
+ } while (offset < BITS_PER_PAGE && pid < pid_max);
}
if (map < &pid_ns->pidmap[(pid_max-1)/BITS_PER_PAGE]) {
++map;
return -1;
}
-int next_pidmap(struct pid_namespace *pid_ns, int last)
+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 (type = 0; type < PIDTYPE_MAX; ++type)
INIT_HLIST_HEAD(&pid->tasks[type]);
+ upid = pid->numbers + ns->level;
spin_lock_irq(&pidmap_lock);
- for (i = ns->level; i >= 0; i--) {
- upid = &pid->numbers[i];
+ for ( ; upid >= pid->numbers; --upid)
hlist_add_head_rcu(&upid->pid_chain,
&pid_hash[pid_hashfn(upid->nr, upid->ns)]);
- }
spin_unlock_irq(&pidmap_lock);
out:
struct task_struct *result = NULL;
if (pid) {
struct hlist_node *first;
- first = rcu_dereference(pid->tasks[type].first);
+ first = rcu_dereference_check(hlist_first_rcu(&pid->tasks[type]),
+ rcu_read_lock_held() ||
+ lockdep_tasklist_lock_is_held());
if (first)
result = hlist_entry(first, struct task_struct, pids[(type)].node);
}
EXPORT_SYMBOL(pid_task);
/*
- * Must be called under rcu_read_lock() or with tasklist_lock read-held.
+ * Must be called under rcu_read_lock().
*/
-struct task_struct *find_task_by_pid_type_ns(int type, int nr,
- struct pid_namespace *ns)
+struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)
{
- return pid_task(find_pid_ns(nr, ns), type);
+ rcu_lockdep_assert(rcu_read_lock_held());
+ return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID);
}
-EXPORT_SYMBOL(find_task_by_pid_type_ns);
-
struct task_struct *find_task_by_vpid(pid_t vnr)
{
- return find_task_by_pid_type_ns(PIDTYPE_PID, vnr,
- current->nsproxy->pid_ns);
+ return find_task_by_pid_ns(vnr, current->nsproxy->pid_ns);
}
-EXPORT_SYMBOL(find_task_by_vpid);
-
-struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)
-{
- return find_task_by_pid_type_ns(PIDTYPE_PID, nr, ns);
-}
-EXPORT_SYMBOL(find_task_by_pid_ns);
struct pid *get_task_pid(struct task_struct *task, enum pid_type type)
{
void __init pidhash_init(void)
{
int i, pidhash_size;
- unsigned long megabytes = nr_kernel_pages >> (20 - PAGE_SHIFT);
- pidhash_shift = max(4, fls(megabytes * 4));
- pidhash_shift = min(12, pidhash_shift);
+ pid_hash = alloc_large_system_hash("PID", sizeof(*pid_hash), 0, 18,
+ HASH_EARLY | HASH_SMALL,
+ &pidhash_shift, NULL, 4096);
pidhash_size = 1 << pidhash_shift;
- printk("PID hash table entries: %d (order: %d, %Zd bytes)\n",
- pidhash_size, pidhash_shift,
- pidhash_size * sizeof(struct hlist_head));
-
- pid_hash = alloc_bootmem(pidhash_size * sizeof(*(pid_hash)));
- if (!pid_hash)
- panic("Could not alloc pidhash!\n");
for (i = 0; i < pidhash_size; i++)
INIT_HLIST_HEAD(&pid_hash[i]);
}
void __init pidmap_init(void)
{
+ /* bump default and minimum pid_max based on number of cpus */
+ pid_max = min(pid_max_max, max_t(int, pid_max,
+ PIDS_PER_CPU_DEFAULT * num_possible_cpus()));
+ pid_max_min = max_t(int, pid_max_min,
+ PIDS_PER_CPU_MIN * num_possible_cpus());
+ pr_info("pid_max: default: %u minimum: %u\n", pid_max, pid_max_min);
+
init_pid_ns.pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
/* Reserve PID 0. We never call free_pidmap(0) */
set_bit(0, init_pid_ns.pidmap[0].page);
projects / linux-flexiantxendom0-natty.git / blobdiff