diff options
Diffstat (limited to 'kernel/pid.c')
| -rw-r--r-- | kernel/pid.c | 134 |
1 files changed, 86 insertions, 48 deletions
diff --git a/kernel/pid.c b/kernel/pid.c index 39b65b69584..9b9a2669814 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -1,8 +1,8 @@ /* * Generic pidhash and scalable, time-bounded PID allocator * - * (C) 2002-2003 William Irwin, IBM - * (C) 2004 William Irwin, Oracle + * (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 @@ -27,7 +27,7 @@ */ #include <linux/mm.h> -#include <linux/module.h> +#include <linux/export.h> #include <linux/slab.h> #include <linux/init.h> #include <linux/rculist.h> @@ -36,6 +36,8 @@ #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) @@ -50,9 +52,6 @@ int pid_max = PID_MAX_DEFAULT; int pid_max_min = RESERVED_PIDS + 1; int pid_max_max = PID_MAX_LIMIT; -#define BITS_PER_PAGE (PAGE_SIZE*8) -#define BITS_PER_PAGE_MASK (BITS_PER_PAGE-1) - static inline int mk_pid(struct pid_namespace *pid_ns, struct pidmap *map, int off) { @@ -76,26 +75,14 @@ struct pid_namespace init_pid_ns = { [ 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, + .proc_inum = PROC_PID_INIT_INO, }; EXPORT_SYMBOL_GPL(init_pid_ns); -int is_container_init(struct task_struct *tsk) -{ - int ret = 0; - struct pid *pid; - - rcu_read_lock(); - pid = task_pid(tsk); - if (pid != NULL && pid->numbers[pid->level].nr == 1) - ret = 1; - rcu_read_unlock(); - - return ret; -} -EXPORT_SYMBOL(is_container_init); - /* * Note: disable interrupts while the pidmap_lock is held as an * interrupt might come in and do read_lock(&tasklist_lock). @@ -137,7 +124,9 @@ static int pid_before(int base, int a, int b) } /* - * We might be racing with someone else trying to set pid_ns->last_pid. + * 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. * @@ -193,15 +182,19 @@ static int alloc_pidmap(struct pid_namespace *pid_ns) break; } if (likely(atomic_read(&map->nr_free))) { - do { + 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); - } while (offset < BITS_PER_PAGE && pid < pid_max); + if (pid >= pid_max) + break; + } } if (map < &pid_ns->pidmap[(pid_max-1)/BITS_PER_PAGE]) { ++map; @@ -217,11 +210,14 @@ static int alloc_pidmap(struct pid_namespace *pid_ns) 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]; @@ -264,8 +260,29 @@ void free_pid(struct pid *pid) unsigned long flags; spin_lock_irqsave(&pidmap_lock, flags); - for (i = 0; i <= pid->level; i++) - hlist_del_rcu(&pid->numbers[i].pid_chain); + 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++) @@ -287,6 +304,7 @@ struct pid *alloc_pid(struct pid_namespace *ns) goto out; tmp = ns; + pid->level = ns->level; for (i = ns->level; i >= 0; i--) { nr = alloc_pidmap(tmp); if (nr < 0) @@ -297,22 +315,32 @@ struct pid *alloc_pid(struct pid_namespace *ns) tmp = tmp->parent; } + if (unlikely(is_child_reaper(pid))) { + if (pid_ns_prepare_proc(ns)) + goto out_free; + } + get_pid_ns(ns); - pid->level = ns->level; 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); - for ( ; upid >= pid->numbers; --upid) + 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); out_free: while (++i <= ns->level) free_pidmap(pid->numbers + i); @@ -322,12 +350,18 @@ out_free: 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 hlist_node *elem; struct upid *pnr; - hlist_for_each_entry_rcu(pnr, elem, + 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, @@ -339,21 +373,17 @@ EXPORT_SYMBOL_GPL(find_pid_ns); struct pid *find_vpid(int nr) { - return find_pid_ns(nr, current->nsproxy->pid_ns); + 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 *pid) +void attach_pid(struct task_struct *task, enum pid_type type) { - struct pid_link *link; - - link = &task->pids[type]; - link->pid = pid; - hlist_add_head_rcu(&link->node, &pid->tasks[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, @@ -385,7 +415,7 @@ void change_pid(struct task_struct *task, enum pid_type type, struct pid *pid) { __change_pid(task, type, pid); - attach_pid(task, type, pid); + attach_pid(task, type); } /* transfer_pid is an optimization of attach_pid(new), detach_pid(old) */ @@ -402,7 +432,6 @@ struct task_struct *pid_task(struct pid *pid, enum pid_type type) if (pid) { struct hlist_node *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); @@ -416,13 +445,15 @@ EXPORT_SYMBOL(pid_task); */ struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns) { - rcu_lockdep_assert(rcu_read_lock_held()); + rcu_lockdep_assert(rcu_read_lock_held(), + "find_task_by_pid_ns() needs rcu_read_lock()" + " protection"); return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID); } struct task_struct *find_task_by_vpid(pid_t vnr) { - return find_task_by_pid_ns(vnr, current->nsproxy->pid_ns); + return find_task_by_pid_ns(vnr, task_active_pid_ns(current)); } struct pid *get_task_pid(struct task_struct *task, enum pid_type type) @@ -435,6 +466,7 @@ struct pid *get_task_pid(struct task_struct *task, enum pid_type type) rcu_read_unlock(); return pid; } +EXPORT_SYMBOL_GPL(get_task_pid); struct task_struct *get_pid_task(struct pid *pid, enum pid_type type) { @@ -446,6 +478,7 @@ struct task_struct *get_pid_task(struct pid *pid, enum pid_type type) rcu_read_unlock(); return result; } +EXPORT_SYMBOL_GPL(get_pid_task); struct pid *find_get_pid(pid_t nr) { @@ -471,10 +504,11 @@ pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns) } return nr; } +EXPORT_SYMBOL_GPL(pid_nr_ns); pid_t pid_vnr(struct pid *pid) { - return pid_nr_ns(pid, current->nsproxy->pid_ns); + return pid_nr_ns(pid, task_active_pid_ns(current)); } EXPORT_SYMBOL_GPL(pid_vnr); @@ -485,7 +519,7 @@ pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type, rcu_read_lock(); if (!ns) - ns = current->nsproxy->pid_ns; + ns = task_active_pid_ns(current); if (likely(pid_alive(task))) { if (type != PIDTYPE_PID) task = task->group_leader; @@ -535,12 +569,13 @@ struct pid *find_ge_pid(int nr, struct pid_namespace *ns) */ void __init pidhash_init(void) { - int i, pidhash_size; + unsigned int i, pidhash_size; 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; + &pidhash_shift, NULL, + 0, 4096); + pidhash_size = 1U << pidhash_shift; for (i = 0; i < pidhash_size; i++) INIT_HLIST_HEAD(&pid_hash[i]); @@ -548,6 +583,9 @@ void __init pidhash_init(void) void __init pidmap_init(void) { + /* Veryify no one has done anything silly */ + BUILD_BUG_ON(PID_MAX_LIMIT >= PIDNS_HASH_ADDING); + /* 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())); |