X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=kernel%2Fpid.c;h=5eeb50538164de353554fe235115673dc031c787;hb=7172c64a7cee4dfa95864f49c914f7ea8cf497c8;hp=23706b226f3ad8149984328b95fe73f3742089ea;hpb=9213980e6a70d8473e0ffd4b39ab5b6caaba9ff5;p=linux-2.6.git

diff --git a/kernel/pid.c b/kernel/pid.c
index 23706b226..5eeb50538 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -1,8 +1,9 @@
 /*
  * Generic pidhash and scalable, time-bounded PID allocator
  *
- * (C) 2002 William Irwin, IBM
- * (C) 2002 Ingo Molnar, Red Hat
+ * (C) 2002-2003 William Irwin, IBM
+ * (C) 2004 William Irwin, 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
@@ -28,17 +29,24 @@
 #include <linux/vs_cvirt.h>
 
 #define pid_hashfn(nr) hash_long((unsigned long)nr, pidhash_shift)
-static struct list_head *pid_hash[PIDTYPE_MAX];
+static struct hlist_head *pid_hash;
 static int pidhash_shift;
+static kmem_cache_t *pid_cachep;
 
 int pid_max = PID_MAX_DEFAULT;
 int last_pid;
 
 #define RESERVED_PIDS		300
 
-#define PIDMAP_ENTRIES		(PID_MAX_LIMIT/PAGE_SIZE/8)
+int pid_max_min = RESERVED_PIDS + 1;
+int pid_max_max = PID_MAX_LIMIT;
+
+#define PIDMAP_ENTRIES		((PID_MAX_LIMIT + 8*PAGE_SIZE - 1)/PAGE_SIZE/8)
 #define BITS_PER_PAGE		(PAGE_SIZE*8)
 #define BITS_PER_PAGE_MASK	(BITS_PER_PAGE-1)
+#define mk_pid(map, off)	(((map) - pidmap_array)*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
@@ -54,11 +62,22 @@ typedef struct pidmap {
 static pidmap_t pidmap_array[PIDMAP_ENTRIES] =
 	 { [ 0 ... PIDMAP_ENTRIES-1 ] = { ATOMIC_INIT(BITS_PER_PAGE), NULL } };
 
-static pidmap_t *map_limit = pidmap_array + PIDMAP_ENTRIES;
-
-static spinlock_t pidmap_lock __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
+/*
+ * 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);
 
-fastcall void free_pidmap(int pid)
+static fastcall void free_pidmap(int pid)
 {
 	pidmap_t *map = pidmap_array + pid / BITS_PER_PAGE;
 	int offset = pid & BITS_PER_PAGE_MASK;
@@ -67,202 +86,227 @@ fastcall void free_pidmap(int pid)
 	atomic_inc(&map->nr_free);
 }
 
-/*
- * Here we search for the next map that has free bits left.
- * Normally the next map has free PIDs.
- */
-static inline pidmap_t *next_free_map(pidmap_t *map, int *max_steps)
+static int alloc_pidmap(void)
 {
-	while (--*max_steps) {
-		if (++map == map_limit)
-			map = pidmap_array;
+	int i, offset, max_scan, pid, last = last_pid;
+	pidmap_t *map;
+
+	pid = last + 1;
+	if (pid >= pid_max)
+		pid = RESERVED_PIDS;
+	offset = pid & BITS_PER_PAGE_MASK;
+	map = &pidmap_array[pid/BITS_PER_PAGE];
+	max_scan = (pid_max + BITS_PER_PAGE - 1)/BITS_PER_PAGE - !offset;
+	for (i = 0; i <= max_scan; ++i) {
 		if (unlikely(!map->page)) {
 			unsigned long page = get_zeroed_page(GFP_KERNEL);
 			/*
 			 * Free the page if someone raced with us
 			 * installing it:
 			 */
-			spin_lock(&pidmap_lock);
+			spin_lock_irq(&pidmap_lock);
 			if (map->page)
 				free_page(page);
 			else
 				map->page = (void *)page;
-			spin_unlock(&pidmap_lock);
-
-			if (!map->page)
+			spin_unlock_irq(&pidmap_lock);
+			if (unlikely(!map->page))
+				break;
+		}
+		if (likely(atomic_read(&map->nr_free))) {
+			do {
+				if (!test_and_set_bit(offset, map->page)) {
+					atomic_dec(&map->nr_free);
+					last_pid = pid;
+					return pid;
+				}
+				offset = find_next_offset(map, offset);
+				pid = mk_pid(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)));
+		}
+		if (map < &pidmap_array[(pid_max-1)/BITS_PER_PAGE]) {
+			++map;
+			offset = 0;
+		} else {
+			map = &pidmap_array[0];
+			offset = RESERVED_PIDS;
+			if (unlikely(last == offset))
 				break;
 		}
-		if (atomic_read(&map->nr_free))
-			return map;
+		pid = mk_pid(map, offset);
 	}
-	return NULL;
+	return -1;
 }
 
-int alloc_pidmap(void)
+fastcall void put_pid(struct pid *pid)
 {
-	int pid, offset, max_steps = PIDMAP_ENTRIES + 1;
-	pidmap_t *map;
+	if (!pid)
+		return;
+	if ((atomic_read(&pid->count) == 1) ||
+	     atomic_dec_and_test(&pid->count))
+		kmem_cache_free(pid_cachep, pid);
+}
 
-	pid = last_pid + 1;
-	if (pid >= pid_max)
-		pid = RESERVED_PIDS;
+static void delayed_put_pid(struct rcu_head *rhp)
+{
+	struct pid *pid = container_of(rhp, struct pid, rcu);
+	put_pid(pid);
+}
 
-	offset = pid & BITS_PER_PAGE_MASK;
-	map = pidmap_array + pid / BITS_PER_PAGE;
-
-	if (likely(map->page && !test_and_set_bit(offset, map->page))) {
-		/*
-		 * There is a small window for last_pid updates to race,
-		 * but in that case the next allocation will go into the
-		 * slowpath and that fixes things up.
-		 */
-return_pid:
-		atomic_dec(&map->nr_free);
-		last_pid = pid;
-		return pid;
-	}
-	
-	if (!offset || !atomic_read(&map->nr_free)) {
-next_map:
-		map = next_free_map(map, &max_steps);
-		if (!map)
-			goto failure;
-		offset = 0;
-	}
-	/*
-	 * Find the next zero bit:
-	 */
-scan_more:
-	offset = find_next_zero_bit(map->page, BITS_PER_PAGE, offset);
-	if (offset >= BITS_PER_PAGE)
-		goto next_map;
-	if (test_and_set_bit(offset, map->page))
-		goto scan_more;
-
-	/* we got the PID: */
-	pid = (map - pidmap_array) * BITS_PER_PAGE + offset;
-	goto return_pid;
-
-failure:
-	return -1;
+fastcall void free_pid(struct pid *pid)
+{
+	/* We can be called with write_lock_irq(&tasklist_lock) held */
+	unsigned long flags;
+
+	spin_lock_irqsave(&pidmap_lock, flags);
+	hlist_del_rcu(&pid->pid_chain);
+	spin_unlock_irqrestore(&pidmap_lock, flags);
+
+	free_pidmap(pid->nr);
+	call_rcu(&pid->rcu, delayed_put_pid);
+}
+
+struct pid *alloc_pid(void)
+{
+	struct pid *pid;
+	enum pid_type type;
+	int nr = -1;
+
+	pid = kmem_cache_alloc(pid_cachep, GFP_KERNEL);
+	if (!pid)
+		goto out;
+
+	nr = alloc_pidmap();
+	if (nr < 0)
+		goto out_free;
+
+	atomic_set(&pid->count, 1);
+	pid->nr = nr;
+	for (type = 0; type < PIDTYPE_MAX; ++type)
+		INIT_HLIST_HEAD(&pid->tasks[type]);
+
+	spin_lock_irq(&pidmap_lock);
+	hlist_add_head_rcu(&pid->pid_chain, &pid_hash[pid_hashfn(pid->nr)]);
+	spin_unlock_irq(&pidmap_lock);
+
+out:
+	return pid;
+
+out_free:
+	kmem_cache_free(pid_cachep, pid);
+	pid = NULL;
+	goto out;
 }
 
-fastcall struct pid *find_pid(enum pid_type type, int nr)
+struct pid * fastcall find_pid(int nr)
 {
-	struct list_head *elem, *bucket = &pid_hash[type][pid_hashfn(nr)];
+	struct hlist_node *elem;
 	struct pid *pid;
 
-	__list_for_each(elem, bucket) {
-		pid = list_entry(elem, struct pid, hash_chain);
+	hlist_for_each_entry_rcu(pid, elem,
+			&pid_hash[pid_hashfn(nr)], pid_chain) {
 		if (pid->nr == nr)
 			return pid;
 	}
 	return NULL;
 }
 
-void fastcall link_pid(task_t *task, struct pid_link *link, struct pid *pid)
+int fastcall attach_pid(struct task_struct *task, enum pid_type type, int nr)
 {
-	atomic_inc(&pid->count);
-	list_add_tail(&link->pid_chain, &pid->task_list);
-	link->pidptr = pid;
-}
+	struct pid_link *link;
+	struct pid *pid;
 
-int fastcall attach_pid(task_t *task, enum pid_type type, int nr)
-{
-	struct pid *pid = find_pid(type, nr);
-
-	if (pid)
-		atomic_inc(&pid->count);
-	else {
-		pid = &task->pids[type].pid;
-		pid->nr = nr;
-		atomic_set(&pid->count, 1);
-		INIT_LIST_HEAD(&pid->task_list);
-		pid->task = task;
-		get_task_struct(task);
-		list_add(&pid->hash_chain, &pid_hash[type][pid_hashfn(nr)]);
-	}
-	list_add_tail(&task->pids[type].pid_chain, &pid->task_list);
-	task->pids[type].pidptr = pid;
+	WARN_ON(!task->pid); /* to be removed soon */
+	WARN_ON(!nr); /* to be removed soon */
+
+	link = &task->pids[type];
+	link->pid = pid = find_pid(nr);
+	hlist_add_head_rcu(&link->node, &pid->tasks[type]);
 
 	return 0;
 }
 
-static inline int __detach_pid(task_t *task, enum pid_type type)
+void fastcall detach_pid(struct task_struct *task, enum pid_type type)
 {
-	struct pid_link *link = task->pids + type;
-	struct pid *pid = link->pidptr;
-	int nr;
+	struct pid_link *link;
+	struct pid *pid;
+	int tmp;
+
+	link = &task->pids[type];
+	pid = link->pid;
 
-	list_del(&link->pid_chain);
-	if (!atomic_dec_and_test(&pid->count))
-		return 0;
+	hlist_del_rcu(&link->node);
+	link->pid = NULL;
 
-	nr = pid->nr;
-	list_del(&pid->hash_chain);
-	put_task_struct(pid->task);
+	for (tmp = PIDTYPE_MAX; --tmp >= 0; )
+		if (!hlist_empty(&pid->tasks[tmp]))
+			return;
 
-	return nr;
+	free_pid(pid);
 }
 
-static void _detach_pid(task_t *task, enum pid_type type)
+struct task_struct * fastcall pid_task(struct pid *pid, enum pid_type type)
 {
-	__detach_pid(task, type);
+	struct task_struct *result = NULL;
+	if (pid) {
+		struct hlist_node *first;
+		first = rcu_dereference(pid->tasks[type].first);
+		if (first)
+			result = hlist_entry(first, struct task_struct, pids[(type)].node);
+		if (result && (pid->nr != 1) &&
+			!vx_check(vx_task_xid(result), VX_WATCH|VX_ADMIN|VX_IDENT)) {
+			vxwprintk((type == PIDTYPE_PID) && (current->xid),
+				"pid_task(%d,%d): task %p[#%u,%u] did lookup %p[#%u,%u]",
+				pid->nr, type, current, vx_current_xid(), current->pid,
+				result, vx_task_xid(result), result->pid);
+			result = NULL;
+		}
+	}
+	return result;
 }
 
-void fastcall detach_pid(task_t *task, enum pid_type type)
+/*
+ * Must be called under rcu_read_lock() or with tasklist_lock read-held.
+ */
+struct task_struct *find_task_by_pid_type(int type, int nr)
 {
-	int nr = __detach_pid(task, type);
+	if (type == PIDTYPE_PID)
+		nr = vx_rmap_pid(nr);
+	else if (type == PIDTYPE_REALPID)
+		type = PIDTYPE_PID;
+	return pid_task(find_pid(nr), type);
+}
 
-	if (!nr)
-		return;
+EXPORT_SYMBOL(find_task_by_pid_type);
 
-	for (type = 0; type < PIDTYPE_MAX; ++type)
-		if (find_pid(type, nr))
-			return;
-	free_pidmap(nr);
+struct task_struct *fastcall get_pid_task(struct pid *pid, enum pid_type type)
+{
+	struct task_struct *result;
+	rcu_read_lock();
+	result = pid_task(pid, type);
+	if (result)
+		get_task_struct(result);
+	rcu_read_unlock();
+	return result;
 }
 
-task_t *find_task_by_pid(int nr)
+struct pid *find_get_pid(pid_t nr)
 {
-	struct pid *pid = find_pid(PIDTYPE_PID,
-		vx_rmap_tgid(current->vx_info, nr));
-
-	if (!pid)
-		return NULL;
-	return pid_task(pid->task_list.next, PIDTYPE_PID);
-}
+	struct pid *pid;
 
-EXPORT_SYMBOL(find_task_by_pid);
+	rcu_read_lock();
+	pid = get_pid(find_pid(nr));
+	rcu_read_unlock();
 
-/*
- * This function switches the PIDs if a non-leader thread calls
- * sys_execve() - this must be done without releasing the PID.
- * (which a detach_pid() would eventually do.)
- */
-void switch_exec_pids(task_t *leader, task_t *thread)
-{
-	_detach_pid(leader, PIDTYPE_PID);
-	_detach_pid(leader, PIDTYPE_TGID);
-	_detach_pid(leader, PIDTYPE_PGID);
-	_detach_pid(leader, PIDTYPE_SID);
-
-	_detach_pid(thread, PIDTYPE_PID);
-	_detach_pid(thread, PIDTYPE_TGID);
-
-	leader->pid = leader->tgid = thread->pid;
-	thread->pid = thread->tgid;
-
-	attach_pid(thread, PIDTYPE_PID, thread->pid);
-	attach_pid(thread, PIDTYPE_TGID, thread->tgid);
-	attach_pid(thread, PIDTYPE_PGID, thread->signal->pgrp);
-	attach_pid(thread, PIDTYPE_SID, thread->signal->session);
-	list_add_tail(&thread->tasks, &init_task.tasks);
-
-	attach_pid(leader, PIDTYPE_PID, leader->pid);
-	attach_pid(leader, PIDTYPE_TGID, leader->tgid);
-	attach_pid(leader, PIDTYPE_PGID, leader->signal->pgrp);
-	attach_pid(leader, PIDTYPE_SID, leader->signal->session);
+	return pid;
 }
 
 /*
@@ -272,39 +316,32 @@ void switch_exec_pids(task_t *leader, task_t *thread)
  */
 void __init pidhash_init(void)
 {
-	int i, j, pidhash_size;
-	unsigned long megabytes = max_pfn >> (20 - PAGE_SHIFT);
+	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);
 	pidhash_size = 1 << pidhash_shift;
 
-	printk("PID hash table entries: %d (order %d: %Zd bytes)\n",
+	printk("PID hash table entries: %d (order: %d, %Zd bytes)\n",
 		pidhash_size, pidhash_shift,
-		pidhash_size * sizeof(struct list_head));
-
-	for (i = 0; i < PIDTYPE_MAX; i++) {
-		pid_hash[i] = alloc_bootmem(pidhash_size *
-					sizeof(struct list_head));
-		if (!pid_hash[i])
-			panic("Could not alloc pidhash!\n");
-		for (j = 0; j < pidhash_size; j++)
-			INIT_LIST_HEAD(&pid_hash[i][j]);
-	}
+		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)
 {
-	int i;
-
 	pidmap_array->page = (void *)get_zeroed_page(GFP_KERNEL);
+	/* Reserve PID 0. We never call free_pidmap(0) */
 	set_bit(0, pidmap_array->page);
 	atomic_dec(&pidmap_array->nr_free);
 
-	/*
-	 * Allocate PID 0, and hash it via all PID types:
-	 */
-
-	for (i = 0; i < PIDTYPE_MAX; i++)
-		attach_pid(current, i, 0);
+	pid_cachep = kmem_cache_create("pid", sizeof(struct pid),
+					__alignof__(struct pid),
+					SLAB_PANIC, NULL, NULL);
 }