* SMP-threaded, sysctl's added
* (c) 1999 Manfred Spraul <manfred@colorfullife.com>
* Enforced range limit on SEM_UNDO
- * (c) 2001 Red Hat Inc <alan@redhat.com>
+ * (c) 2001 Red Hat Inc
* Lockless wakeup
* (c) 2003 Manfred Spraul <manfred@colorfullife.com>
*
void sem_exit_ns(struct ipc_namespace *ns)
{
free_ipcs(ns, &sem_ids(ns), freeary);
+ idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
}
#endif
}
/*
- * This routine is called in the paths where the rw_mutex is held to protect
- * access to the idr tree.
- */
-static inline struct sem_array *sem_lock_check_down(struct ipc_namespace *ns,
- int id)
-{
- struct kern_ipc_perm *ipcp = ipc_lock_check_down(&sem_ids(ns), id);
-
- if (IS_ERR(ipcp))
- return (struct sem_array *)ipcp;
-
- return container_of(ipcp, struct sem_array, sem_perm);
-}
-
-/*
* sem_lock_(check_) routines are called in the paths where the rw_mutex
* is not held.
*/
return container_of(ipcp, struct sem_array, sem_perm);
}
+static inline void sem_lock_and_putref(struct sem_array *sma)
+{
+ ipc_lock_by_ptr(&sma->sem_perm);
+ ipc_rcu_putref(sma);
+}
+
+static inline void sem_getref_and_unlock(struct sem_array *sma)
+{
+ ipc_rcu_getref(sma);
+ ipc_unlock(&(sma)->sem_perm);
+}
+
+static inline void sem_putref(struct sem_array *sma)
+{
+ ipc_lock_by_ptr(&sma->sem_perm);
+ ipc_rcu_putref(sma);
+ ipc_unlock(&(sma)->sem_perm);
+}
+
static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
{
ipc_rmid(&sem_ids(ns), &s->sem_perm);
key_t key = params->key;
int nsems = params->u.nsems;
int semflg = params->flg;
+ int i;
if (!nsems)
return -EINVAL;
ns->used_sems += nsems;
sma->sem_base = (struct sem *) &sma[1];
- /* sma->sem_pending = NULL; */
- sma->sem_pending_last = &sma->sem_pending;
- /* sma->undo = NULL; */
+
+ for (i = 0; i < nsems; i++)
+ INIT_LIST_HEAD(&sma->sem_base[i].sem_pending);
+
+ sma->complex_count = 0;
+ INIT_LIST_HEAD(&sma->sem_pending);
+ INIT_LIST_HEAD(&sma->list_id);
sma->sem_nsems = nsems;
sma->sem_ctime = get_seconds();
sem_unlock(sma);
return 0;
}
-asmlinkage long sys_semget(key_t key, int nsems, int semflg)
+SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
{
struct ipc_namespace *ns;
struct ipc_ops sem_ops;
return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
}
-/* Manage the doubly linked list sma->sem_pending as a FIFO:
- * insert new queue elements at the tail sma->sem_pending_last.
- */
-static inline void append_to_queue (struct sem_array * sma,
- struct sem_queue * q)
-{
- *(q->prev = sma->sem_pending_last) = q;
- *(sma->sem_pending_last = &q->next) = NULL;
-}
-
-static inline void prepend_to_queue (struct sem_array * sma,
- struct sem_queue * q)
-{
- q->next = sma->sem_pending;
- *(q->prev = &sma->sem_pending) = q;
- if (q->next)
- q->next->prev = &q->next;
- else /* sma->sem_pending_last == &sma->sem_pending */
- sma->sem_pending_last = &q->next;
-}
-
-static inline void remove_from_queue (struct sem_array * sma,
- struct sem_queue * q)
-{
- *(q->prev) = q->next;
- if (q->next)
- q->next->prev = q->prev;
- else /* sma->sem_pending_last == &q->next */
- sma->sem_pending_last = q->prev;
- q->prev = NULL; /* mark as removed */
-}
-
/*
* Determine whether a sequence of semaphore operations would succeed
* all at once. Return 0 if yes, 1 if need to sleep, else return error code.
return result;
}
-/* Go through the pending queue for the indicated semaphore
- * looking for tasks that can be completed.
+/*
+ * Wake up a process waiting on the sem queue with a given error.
+ * The queue is invalid (may not be accessed) after the function returns.
*/
-static void update_queue (struct sem_array * sma)
+static void wake_up_sem_queue(struct sem_queue *q, int error)
{
- int error;
- struct sem_queue * q;
+ /*
+ * Hold preempt off so that we don't get preempted and have the
+ * wakee busy-wait until we're scheduled back on. We're holding
+ * locks here so it may not strictly be needed, however if the
+ * locks become preemptible then this prevents such a problem.
+ */
+ preempt_disable();
+ q->status = IN_WAKEUP;
+ wake_up_process(q->sleeper);
+ /* hands-off: q can disappear immediately after writing q->status. */
+ smp_wmb();
+ q->status = error;
+ preempt_enable();
+}
+
+static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
+{
+ list_del(&q->list);
+ if (q->nsops == 1)
+ list_del(&q->simple_list);
+ else
+ sma->complex_count--;
+}
+
+
+/**
+ * update_queue(sma, semnum): Look for tasks that can be completed.
+ * @sma: semaphore array.
+ * @semnum: semaphore that was modified.
+ *
+ * update_queue must be called after a semaphore in a semaphore array
+ * was modified. If multiple semaphore were modified, then @semnum
+ * must be set to -1.
+ */
+static void update_queue(struct sem_array *sma, int semnum)
+{
+ struct sem_queue *q;
+ struct list_head *walk;
+ struct list_head *pending_list;
+ int offset;
+
+ /* if there are complex operations around, then knowing the semaphore
+ * that was modified doesn't help us. Assume that multiple semaphores
+ * were modified.
+ */
+ if (sma->complex_count)
+ semnum = -1;
+
+ if (semnum == -1) {
+ pending_list = &sma->sem_pending;
+ offset = offsetof(struct sem_queue, list);
+ } else {
+ pending_list = &sma->sem_base[semnum].sem_pending;
+ offset = offsetof(struct sem_queue, simple_list);
+ }
+
+again:
+ walk = pending_list->next;
+ while (walk != pending_list) {
+ int error, alter;
+
+ q = (struct sem_queue *)((char *)walk - offset);
+ walk = walk->next;
+
+ /* If we are scanning the single sop, per-semaphore list of
+ * one semaphore and that semaphore is 0, then it is not
+ * necessary to scan the "alter" entries: simple increments
+ * that affect only one entry succeed immediately and cannot
+ * be in the per semaphore pending queue, and decrements
+ * cannot be successful if the value is already 0.
+ */
+ if (semnum != -1 && sma->sem_base[semnum].semval == 0 &&
+ q->alter)
+ break;
- q = sma->sem_pending;
- while(q) {
error = try_atomic_semop(sma, q->sops, q->nsops,
q->undo, q->pid);
/* Does q->sleeper still need to sleep? */
- if (error <= 0) {
- struct sem_queue *n;
- remove_from_queue(sma,q);
- q->status = IN_WAKEUP;
- /*
- * Continue scanning. The next operation
- * that must be checked depends on the type of the
- * completed operation:
- * - if the operation modified the array, then
- * restart from the head of the queue and
- * check for threads that might be waiting
- * for semaphore values to become 0.
- * - if the operation didn't modify the array,
- * then just continue.
- */
- if (q->alter)
- n = sma->sem_pending;
- else
- n = q->next;
- wake_up_process(q->sleeper);
- /* hands-off: q will disappear immediately after
- * writing q->status.
- */
- smp_wmb();
- q->status = error;
- q = n;
- } else {
- q = q->next;
- }
+ if (error > 0)
+ continue;
+
+ unlink_queue(sma, q);
+
+ /*
+ * The next operation that must be checked depends on the type
+ * of the completed operation:
+ * - if the operation modified the array, then restart from the
+ * head of the queue and check for threads that might be
+ * waiting for the new semaphore values.
+ * - if the operation didn't modify the array, then just
+ * continue.
+ */
+ alter = q->alter;
+ wake_up_sem_queue(q, error);
+ if (alter && !error)
+ goto again;
}
}
struct sem_queue * q;
semncnt = 0;
- for (q = sma->sem_pending; q; q = q->next) {
+ list_for_each_entry(q, &sma->sem_pending, list) {
struct sembuf * sops = q->sops;
int nsops = q->nsops;
int i;
}
return semncnt;
}
+
static int count_semzcnt (struct sem_array * sma, ushort semnum)
{
int semzcnt;
struct sem_queue * q;
semzcnt = 0;
- for (q = sma->sem_pending; q; q = q->next) {
+ list_for_each_entry(q, &sma->sem_pending, list) {
struct sembuf * sops = q->sops;
int nsops = q->nsops;
int i;
return semzcnt;
}
+static void free_un(struct rcu_head *head)
+{
+ struct sem_undo *un = container_of(head, struct sem_undo, rcu);
+ kfree(un);
+}
+
/* Free a semaphore set. freeary() is called with sem_ids.rw_mutex locked
* as a writer and the spinlock for this semaphore set hold. sem_ids.rw_mutex
* remains locked on exit.
*/
static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
{
- struct sem_undo *un;
- struct sem_queue *q;
+ struct sem_undo *un, *tu;
+ struct sem_queue *q, *tq;
struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
- /* Invalidate the existing undo structures for this semaphore set.
- * (They will be freed without any further action in exit_sem()
- * or during the next semop.)
- */
- for (un = sma->undo; un; un = un->id_next)
+ /* Free the existing undo structures for this semaphore set. */
+ assert_spin_locked(&sma->sem_perm.lock);
+ list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
+ list_del(&un->list_id);
+ spin_lock(&un->ulp->lock);
un->semid = -1;
+ list_del_rcu(&un->list_proc);
+ spin_unlock(&un->ulp->lock);
+ call_rcu(&un->rcu, free_un);
+ }
/* Wake up all pending processes and let them fail with EIDRM. */
- q = sma->sem_pending;
- while(q) {
- struct sem_queue *n;
- /* lazy remove_from_queue: we are killing the whole queue */
- q->prev = NULL;
- n = q->next;
- q->status = IN_WAKEUP;
- wake_up_process(q->sleeper); /* doesn't sleep */
- smp_wmb();
- q->status = -EIDRM; /* hands-off q */
- q = n;
+ list_for_each_entry_safe(q, tq, &sma->sem_pending, list) {
+ unlink_queue(sma, q);
+ wake_up_sem_queue(q, -EIDRM);
}
/* Remove the semaphore set from the IDR */
static int semctl_nolock(struct ipc_namespace *ns, int semid,
int cmd, int version, union semun arg)
{
- int err = -EINVAL;
+ int err;
struct sem_array *sma;
switch(cmd) {
default:
return -EINVAL;
}
- return err;
out_unlock:
sem_unlock(sma);
return err;
int i;
if(nsems > SEMMSL_FAST) {
- ipc_rcu_getref(sma);
- sem_unlock(sma);
+ sem_getref_and_unlock(sma);
sem_io = ipc_alloc(sizeof(ushort)*nsems);
if(sem_io == NULL) {
- ipc_lock_by_ptr(&sma->sem_perm);
- ipc_rcu_putref(sma);
- sem_unlock(sma);
+ sem_putref(sma);
return -ENOMEM;
}
- ipc_lock_by_ptr(&sma->sem_perm);
- ipc_rcu_putref(sma);
+ sem_lock_and_putref(sma);
if (sma->sem_perm.deleted) {
sem_unlock(sma);
err = -EIDRM;
int i;
struct sem_undo *un;
- ipc_rcu_getref(sma);
- sem_unlock(sma);
+ sem_getref_and_unlock(sma);
if(nsems > SEMMSL_FAST) {
sem_io = ipc_alloc(sizeof(ushort)*nsems);
if(sem_io == NULL) {
- ipc_lock_by_ptr(&sma->sem_perm);
- ipc_rcu_putref(sma);
- sem_unlock(sma);
+ sem_putref(sma);
return -ENOMEM;
}
}
if (copy_from_user (sem_io, arg.array, nsems*sizeof(ushort))) {
- ipc_lock_by_ptr(&sma->sem_perm);
- ipc_rcu_putref(sma);
- sem_unlock(sma);
+ sem_putref(sma);
err = -EFAULT;
goto out_free;
}
for (i = 0; i < nsems; i++) {
if (sem_io[i] > SEMVMX) {
- ipc_lock_by_ptr(&sma->sem_perm);
- ipc_rcu_putref(sma);
- sem_unlock(sma);
+ sem_putref(sma);
err = -ERANGE;
goto out_free;
}
}
- ipc_lock_by_ptr(&sma->sem_perm);
- ipc_rcu_putref(sma);
+ sem_lock_and_putref(sma);
if (sma->sem_perm.deleted) {
sem_unlock(sma);
err = -EIDRM;
for (i = 0; i < nsems; i++)
sma->sem_base[i].semval = sem_io[i];
- for (un = sma->undo; un; un = un->id_next)
+
+ assert_spin_locked(&sma->sem_perm.lock);
+ list_for_each_entry(un, &sma->list_id, list_id) {
for (i = 0; i < nsems; i++)
un->semadj[i] = 0;
+ }
sma->sem_ctime = get_seconds();
/* maybe some queued-up processes were waiting for this */
- update_queue(sma);
+ update_queue(sma, -1);
err = 0;
goto out_unlock;
}
{
int val = arg.val;
struct sem_undo *un;
+
err = -ERANGE;
if (val > SEMVMX || val < 0)
goto out_unlock;
- for (un = sma->undo; un; un = un->id_next)
+ assert_spin_locked(&sma->sem_perm.lock);
+ list_for_each_entry(un, &sma->list_id, list_id)
un->semadj[semnum] = 0;
+
curr->semval = val;
curr->sempid = task_tgid_vnr(current);
sma->sem_ctime = get_seconds();
/* maybe some queued-up processes were waiting for this */
- update_queue(sma);
+ update_queue(sma, semnum);
err = 0;
goto out_unlock;
}
return err;
}
-struct sem_setbuf {
- uid_t uid;
- gid_t gid;
- mode_t mode;
-};
-
-static inline unsigned long copy_semid_from_user(struct sem_setbuf *out, void __user *buf, int version)
+static inline unsigned long
+copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
{
switch(version) {
case IPC_64:
- {
- struct semid64_ds tbuf;
-
- if(copy_from_user(&tbuf, buf, sizeof(tbuf)))
+ if (copy_from_user(out, buf, sizeof(*out)))
return -EFAULT;
-
- out->uid = tbuf.sem_perm.uid;
- out->gid = tbuf.sem_perm.gid;
- out->mode = tbuf.sem_perm.mode;
-
return 0;
- }
case IPC_OLD:
{
struct semid_ds tbuf_old;
if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
return -EFAULT;
- out->uid = tbuf_old.sem_perm.uid;
- out->gid = tbuf_old.sem_perm.gid;
- out->mode = tbuf_old.sem_perm.mode;
+ out->sem_perm.uid = tbuf_old.sem_perm.uid;
+ out->sem_perm.gid = tbuf_old.sem_perm.gid;
+ out->sem_perm.mode = tbuf_old.sem_perm.mode;
return 0;
}
}
}
-static int semctl_down(struct ipc_namespace *ns, int semid, int semnum,
- int cmd, int version, union semun arg)
+/*
+ * This function handles some semctl commands which require the rw_mutex
+ * to be held in write mode.
+ * NOTE: no locks must be held, the rw_mutex is taken inside this function.
+ */
+static int semctl_down(struct ipc_namespace *ns, int semid,
+ int cmd, int version, union semun arg)
{
struct sem_array *sma;
int err;
- struct sem_setbuf uninitialized_var(setbuf);
+ struct semid64_ds semid64;
struct kern_ipc_perm *ipcp;
if(cmd == IPC_SET) {
- if(copy_semid_from_user (&setbuf, arg.buf, version))
+ if (copy_semid_from_user(&semid64, arg.buf, version))
return -EFAULT;
}
- sma = sem_lock_check_down(ns, semid);
- if (IS_ERR(sma))
- return PTR_ERR(sma);
- ipcp = &sma->sem_perm;
-
- err = audit_ipc_obj(ipcp);
- if (err)
- goto out_unlock;
+ ipcp = ipcctl_pre_down(&sem_ids(ns), semid, cmd, &semid64.sem_perm, 0);
+ if (IS_ERR(ipcp))
+ return PTR_ERR(ipcp);
- if (cmd == IPC_SET) {
- err = audit_ipc_set_perm(0, setbuf.uid, setbuf.gid, setbuf.mode);
- if (err)
- goto out_unlock;
- }
- if (current->euid != ipcp->cuid &&
- current->euid != ipcp->uid && !capable(CAP_SYS_ADMIN)) {
- err=-EPERM;
- goto out_unlock;
- }
+ sma = container_of(ipcp, struct sem_array, sem_perm);
err = security_sem_semctl(sma, cmd);
if (err)
switch(cmd){
case IPC_RMID:
freeary(ns, ipcp);
- err = 0;
- break;
+ goto out_up;
case IPC_SET:
- ipcp->uid = setbuf.uid;
- ipcp->gid = setbuf.gid;
- ipcp->mode = (ipcp->mode & ~S_IRWXUGO)
- | (setbuf.mode & S_IRWXUGO);
+ ipc_update_perm(&semid64.sem_perm, ipcp);
sma->sem_ctime = get_seconds();
- sem_unlock(sma);
- err = 0;
break;
default:
- sem_unlock(sma);
err = -EINVAL;
- break;
}
- return err;
out_unlock:
sem_unlock(sma);
+out_up:
+ up_write(&sem_ids(ns).rw_mutex);
return err;
}
-asmlinkage long sys_semctl (int semid, int semnum, int cmd, union semun arg)
+SYSCALL_DEFINE(semctl)(int semid, int semnum, int cmd, union semun arg)
{
int err = -EINVAL;
int version;
return err;
case IPC_RMID:
case IPC_SET:
- down_write(&sem_ids(ns).rw_mutex);
- err = semctl_down(ns,semid,semnum,cmd,version,arg);
- up_write(&sem_ids(ns).rw_mutex);
+ err = semctl_down(ns, semid, cmd, version, arg);
return err;
default:
return -EINVAL;
}
}
+#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
+asmlinkage long SyS_semctl(int semid, int semnum, int cmd, union semun arg)
+{
+ return SYSC_semctl((int) semid, (int) semnum, (int) cmd, arg);
+}
+SYSCALL_ALIAS(sys_semctl, SyS_semctl);
+#endif
/* If the task doesn't already have a undo_list, then allocate one
* here. We guarantee there is only one thread using this undo list,
return -ENOMEM;
spin_lock_init(&undo_list->lock);
atomic_set(&undo_list->refcnt, 1);
+ INIT_LIST_HEAD(&undo_list->list_proc);
+
current->sysvsem.undo_list = undo_list;
}
*undo_listp = undo_list;
return 0;
}
+static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
+{
+ struct sem_undo *un;
+
+ list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) {
+ if (un->semid == semid)
+ return un;
+ }
+ return NULL;
+}
+
static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
{
- struct sem_undo **last, *un;
+ struct sem_undo *un;
- last = &ulp->proc_list;
- un = *last;
- while(un != NULL) {
- if(un->semid==semid)
- break;
- if(un->semid==-1) {
- *last=un->proc_next;
- kfree(un);
- } else {
- last=&un->proc_next;
- }
- un=*last;
+ assert_spin_locked(&ulp->lock);
+
+ un = __lookup_undo(ulp, semid);
+ if (un) {
+ list_del_rcu(&un->list_proc);
+ list_add_rcu(&un->list_proc, &ulp->list_proc);
}
return un;
}
-static struct sem_undo *find_undo(struct ipc_namespace *ns, int semid)
+/**
+ * find_alloc_undo - Lookup (and if not present create) undo array
+ * @ns: namespace
+ * @semid: semaphore array id
+ *
+ * The function looks up (and if not present creates) the undo structure.
+ * The size of the undo structure depends on the size of the semaphore
+ * array, thus the alloc path is not that straightforward.
+ * Lifetime-rules: sem_undo is rcu-protected, on success, the function
+ * performs a rcu_read_lock().
+ */
+static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
{
struct sem_array *sma;
struct sem_undo_list *ulp;
if (error)
return ERR_PTR(error);
+ rcu_read_lock();
spin_lock(&ulp->lock);
un = lookup_undo(ulp, semid);
spin_unlock(&ulp->lock);
if (likely(un!=NULL))
goto out;
+ rcu_read_unlock();
/* no undo structure around - allocate one. */
+ /* step 1: figure out the size of the semaphore array */
sma = sem_lock_check(ns, semid);
if (IS_ERR(sma))
return ERR_PTR(PTR_ERR(sma));
nsems = sma->sem_nsems;
- ipc_rcu_getref(sma);
- sem_unlock(sma);
+ sem_getref_and_unlock(sma);
+ /* step 2: allocate new undo structure */
new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
if (!new) {
- ipc_lock_by_ptr(&sma->sem_perm);
- ipc_rcu_putref(sma);
- sem_unlock(sma);
+ sem_putref(sma);
return ERR_PTR(-ENOMEM);
}
- new->semadj = (short *) &new[1];
- new->semid = semid;
- spin_lock(&ulp->lock);
- un = lookup_undo(ulp, semid);
- if (un) {
- spin_unlock(&ulp->lock);
- kfree(new);
- ipc_lock_by_ptr(&sma->sem_perm);
- ipc_rcu_putref(sma);
- sem_unlock(sma);
- goto out;
- }
- ipc_lock_by_ptr(&sma->sem_perm);
- ipc_rcu_putref(sma);
+ /* step 3: Acquire the lock on semaphore array */
+ sem_lock_and_putref(sma);
if (sma->sem_perm.deleted) {
sem_unlock(sma);
- spin_unlock(&ulp->lock);
kfree(new);
un = ERR_PTR(-EIDRM);
goto out;
}
- new->proc_next = ulp->proc_list;
- ulp->proc_list = new;
- new->id_next = sma->undo;
- sma->undo = new;
- sem_unlock(sma);
+ spin_lock(&ulp->lock);
+
+ /*
+ * step 4: check for races: did someone else allocate the undo struct?
+ */
+ un = lookup_undo(ulp, semid);
+ if (un) {
+ kfree(new);
+ goto success;
+ }
+ /* step 5: initialize & link new undo structure */
+ new->semadj = (short *) &new[1];
+ new->ulp = ulp;
+ new->semid = semid;
+ assert_spin_locked(&ulp->lock);
+ list_add_rcu(&new->list_proc, &ulp->list_proc);
+ assert_spin_locked(&sma->sem_perm.lock);
+ list_add(&new->list_id, &sma->list_id);
un = new;
+
+success:
spin_unlock(&ulp->lock);
+ rcu_read_lock();
+ sem_unlock(sma);
out:
return un;
}
-asmlinkage long sys_semtimedop(int semid, struct sembuf __user *tsops,
- unsigned nsops, const struct timespec __user *timeout)
+SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
+ unsigned, nsops, const struct timespec __user *, timeout)
{
int error = -EINVAL;
struct sem_array *sma;
alter = 1;
}
-retry_undos:
if (undos) {
- un = find_undo(ns, semid);
+ un = find_alloc_undo(ns, semid);
if (IS_ERR(un)) {
error = PTR_ERR(un);
goto out_free;
sma = sem_lock_check(ns, semid);
if (IS_ERR(sma)) {
+ if (un)
+ rcu_read_unlock();
error = PTR_ERR(sma);
goto out_free;
}
/*
- * semid identifiers are not unique - find_undo may have
+ * semid identifiers are not unique - find_alloc_undo may have
* allocated an undo structure, it was invalidated by an RMID
- * and now a new array with received the same id. Check and retry.
+ * and now a new array with received the same id. Check and fail.
+ * This case can be detected checking un->semid. The existance of
+ * "un" itself is guaranteed by rcu.
*/
- if (un && un->semid == -1) {
- sem_unlock(sma);
- goto retry_undos;
+ error = -EIDRM;
+ if (un) {
+ if (un->semid == -1) {
+ rcu_read_unlock();
+ goto out_unlock_free;
+ } else {
+ /*
+ * rcu lock can be released, "un" cannot disappear:
+ * - sem_lock is acquired, thus IPC_RMID is
+ * impossible.
+ * - exit_sem is impossible, it always operates on
+ * current (or a dead task).
+ */
+
+ rcu_read_unlock();
+ }
}
+
error = -EFBIG;
if (max >= sma->sem_nsems)
goto out_unlock_free;
error = try_atomic_semop (sma, sops, nsops, un, task_tgid_vnr(current));
if (error <= 0) {
if (alter && error == 0)
- update_queue (sma);
+ update_queue(sma, (nsops == 1) ? sops[0].sem_num : -1);
+
goto out_unlock_free;
}
* task into the pending queue and go to sleep.
*/
- queue.sma = sma;
queue.sops = sops;
queue.nsops = nsops;
queue.undo = un;
queue.pid = task_tgid_vnr(current);
- queue.id = semid;
queue.alter = alter;
if (alter)
- append_to_queue(sma ,&queue);
+ list_add_tail(&queue.list, &sma->sem_pending);
else
- prepend_to_queue(sma ,&queue);
+ list_add(&queue.list, &sma->sem_pending);
+
+ if (nsops == 1) {
+ struct sem *curr;
+ curr = &sma->sem_base[sops->sem_num];
+
+ if (alter)
+ list_add_tail(&queue.simple_list, &curr->sem_pending);
+ else
+ list_add(&queue.simple_list, &curr->sem_pending);
+ } else {
+ INIT_LIST_HEAD(&queue.simple_list);
+ sma->complex_count++;
+ }
queue.status = -EINTR;
queue.sleeper = current;
sma = sem_lock(ns, semid);
if (IS_ERR(sma)) {
- BUG_ON(queue.prev != NULL);
error = -EIDRM;
goto out_free;
}
*/
if (timeout && jiffies_left == 0)
error = -EAGAIN;
- remove_from_queue(sma,&queue);
- goto out_unlock_free;
+ unlink_queue(sma, &queue);
out_unlock_free:
sem_unlock(sma);
return error;
}
-asmlinkage long sys_semop (int semid, struct sembuf __user *tsops, unsigned nsops)
+SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
+ unsigned, nsops)
{
return sys_semtimedop(semid, tsops, nsops, NULL);
}
*/
void exit_sem(struct task_struct *tsk)
{
- struct sem_undo_list *undo_list;
- struct sem_undo *u, **up;
- struct ipc_namespace *ns;
+ struct sem_undo_list *ulp;
- undo_list = tsk->sysvsem.undo_list;
- if (!undo_list)
+ ulp = tsk->sysvsem.undo_list;
+ if (!ulp)
return;
+ tsk->sysvsem.undo_list = NULL;
- if (!atomic_dec_and_test(&undo_list->refcnt))
+ if (!atomic_dec_and_test(&ulp->refcnt))
return;
- ns = tsk->nsproxy->ipc_ns;
- /* There's no need to hold the semundo list lock, as current
- * is the last task exiting for this undo list.
- */
- for (up = &undo_list->proc_list; (u = *up); *up = u->proc_next, kfree(u)) {
+ for (;;) {
struct sem_array *sma;
- int nsems, i;
- struct sem_undo *un, **unp;
+ struct sem_undo *un;
int semid;
-
- semid = u->semid;
+ int i;
- if(semid == -1)
- continue;
- sma = sem_lock(ns, semid);
+ rcu_read_lock();
+ un = list_entry_rcu(ulp->list_proc.next,
+ struct sem_undo, list_proc);
+ if (&un->list_proc == &ulp->list_proc)
+ semid = -1;
+ else
+ semid = un->semid;
+ rcu_read_unlock();
+
+ if (semid == -1)
+ break;
+
+ sma = sem_lock_check(tsk->nsproxy->ipc_ns, un->semid);
+
+ /* exit_sem raced with IPC_RMID, nothing to do */
if (IS_ERR(sma))
continue;
- if (u->semid == -1)
- goto next_entry;
+ un = __lookup_undo(ulp, semid);
+ if (un == NULL) {
+ /* exit_sem raced with IPC_RMID+semget() that created
+ * exactly the same semid. Nothing to do.
+ */
+ sem_unlock(sma);
+ continue;
+ }
+
+ /* remove un from the linked lists */
+ assert_spin_locked(&sma->sem_perm.lock);
+ list_del(&un->list_id);
- BUG_ON(sem_checkid(sma, u->semid));
+ spin_lock(&ulp->lock);
+ list_del_rcu(&un->list_proc);
+ spin_unlock(&ulp->lock);
- /* remove u from the sma->undo list */
- for (unp = &sma->undo; (un = *unp); unp = &un->id_next) {
- if (u == un)
- goto found;
- }
- printk ("exit_sem undo list error id=%d\n", u->semid);
- goto next_entry;
-found:
- *unp = un->id_next;
- /* perform adjustments registered in u */
- nsems = sma->sem_nsems;
- for (i = 0; i < nsems; i++) {
+ /* perform adjustments registered in un */
+ for (i = 0; i < sma->sem_nsems; i++) {
struct sem * semaphore = &sma->sem_base[i];
- if (u->semadj[i]) {
- semaphore->semval += u->semadj[i];
+ if (un->semadj[i]) {
+ semaphore->semval += un->semadj[i];
/*
* Range checks of the new semaphore value,
* not defined by sus:
}
sma->sem_otime = get_seconds();
/* maybe some queued-up processes were waiting for this */
- update_queue(sma);
-next_entry:
+ update_queue(sma, -1);
sem_unlock(sma);
+
+ call_rcu(&un->rcu, free_un);
}
- kfree(undo_list);
+ kfree(ulp);
}
#ifdef CONFIG_PROC_FS
struct sem_array *sma = it;
return seq_printf(s,
- "%10d %10d %4o %10lu %5u %5u %5u %5u %10lu %10lu\n",
+ "%10d %10d %4o %10u %5u %5u %5u %5u %10lu %10lu\n",
sma->sem_perm.key,
sma->sem_perm.id,
sma->sem_perm.mode,
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff