* 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>
*
#include <linux/seq_file.h>
#include <linux/rwsem.h>
#include <linux/nsproxy.h>
+#include <linux/ipc_namespace.h>
#include <asm/uaccess.h>
#include "util.h"
-#define sem_ids(ns) (*((ns)->ids[IPC_SEM_IDS]))
+#define sem_ids(ns) ((ns)->ids[IPC_SEM_IDS])
#define sem_unlock(sma) ipc_unlock(&(sma)->sem_perm)
#define sem_checkid(sma, semid) ipc_checkid(&sma->sem_perm, semid)
-#define sem_buildid(id, seq) ipc_buildid(id, seq)
-
-static struct ipc_ids init_sem_ids;
static int newary(struct ipc_namespace *, struct ipc_params *);
-static void freeary(struct ipc_namespace *, struct sem_array *);
+static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
#ifdef CONFIG_PROC_FS
static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
#endif
#define sc_semopm sem_ctls[2]
#define sc_semmni sem_ctls[3]
-static void __sem_init_ns(struct ipc_namespace *ns, struct ipc_ids *ids)
+void sem_init_ns(struct ipc_namespace *ns)
{
- ns->ids[IPC_SEM_IDS] = ids;
ns->sc_semmsl = SEMMSL;
ns->sc_semmns = SEMMNS;
ns->sc_semopm = SEMOPM;
ns->sc_semmni = SEMMNI;
ns->used_sems = 0;
- ipc_init_ids(ids);
-}
-
-int sem_init_ns(struct ipc_namespace *ns)
-{
- struct ipc_ids *ids;
-
- ids = kmalloc(sizeof(struct ipc_ids), GFP_KERNEL);
- if (ids == NULL)
- return -ENOMEM;
-
- __sem_init_ns(ns, ids);
- return 0;
+ ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
}
+#ifdef CONFIG_IPC_NS
void sem_exit_ns(struct ipc_namespace *ns)
{
- struct sem_array *sma;
- int next_id;
- int total, in_use;
-
- down_write(&sem_ids(ns).rw_mutex);
-
- in_use = sem_ids(ns).in_use;
-
- for (total = 0, next_id = 0; total < in_use; next_id++) {
- sma = idr_find(&sem_ids(ns).ipcs_idr, next_id);
- if (sma == NULL)
- continue;
- ipc_lock_by_ptr(&sma->sem_perm);
- freeary(ns, sma);
- total++;
- }
- up_write(&sem_ids(ns).rw_mutex);
-
- kfree(ns->ids[IPC_SEM_IDS]);
- ns->ids[IPC_SEM_IDS] = NULL;
+ free_ipcs(ns, &sem_ids(ns), freeary);
}
+#endif
void __init sem_init (void)
{
- __sem_init_ns(&init_ipc_ns, &init_sem_ids);
+ sem_init_ns(&init_ipc_ns);
ipc_init_proc_interface("sysvipc/sem",
" key semid perms nsems uid gid cuid cgid otime ctime\n",
IPC_SEM_IDS, sysvipc_sem_proc_show);
}
/*
- * 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);
-
- 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.
*/
{
struct kern_ipc_perm *ipcp = ipc_lock(&sem_ids(ns), id);
+ if (IS_ERR(ipcp))
+ return (struct sem_array *)ipcp;
+
return container_of(ipcp, struct sem_array, sem_perm);
}
{
struct kern_ipc_perm *ipcp = ipc_lock_check(&sem_ids(ns), id);
+ if (IS_ERR(ipcp))
+ return (struct sem_array *)ipcp;
+
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);
}
ns->used_sems += nsems;
- sma->sem_perm.id = sem_buildid(id, sma->sem_perm.seq);
sma->sem_base = (struct sem *) &sma[1];
- /* sma->sem_pending = NULL; */
- sma->sem_pending_last = &sma->sem_pending;
- /* sma->undo = NULL; */
+ 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.
int error;
struct sem_queue * q;
- q = sma->sem_pending;
- while(q) {
+ q = list_entry(sma->sem_pending.next, struct sem_queue, list);
+ while (&q->list != &sma->sem_pending) {
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
* for semaphore values to become 0.
* - if the operation didn't modify the array,
* then just continue.
+ * The order of list_del() and reading ->next
+ * is crucial: In the former case, the list_del()
+ * must be done first [because we might be the
+ * first entry in ->sem_pending], in the latter
+ * case the list_del() must be done last
+ * [because the list is invalid after the list_del()]
*/
- if (q->alter)
- n = sma->sem_pending;
- else
- n = q->next;
+ if (q->alter) {
+ list_del(&q->list);
+ n = list_entry(sma->sem_pending.next,
+ struct sem_queue, list);
+ } else {
+ n = list_entry(q->list.next, struct sem_queue,
+ list);
+ list_del(&q->list);
+ }
+
+ /* wake up the waiting thread */
+ q->status = IN_WAKEUP;
+
wake_up_process(q->sleeper);
/* hands-off: q will disappear immediately after
* writing q->status.
q->status = error;
q = n;
} else {
- q = q->next;
+ q = list_entry(q->list.next, struct sem_queue, list);
}
}
}
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 sem_array *sma)
+static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
{
- struct sem_undo *un;
- struct sem_queue *q;
-
- /* 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)
+ struct sem_undo *un, *tu;
+ struct sem_queue *q, *tq;
+ struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
+
+ /* 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;
+ list_for_each_entry_safe(q, tq, &sma->sem_pending, list) {
+ list_del(&q->list);
+
q->status = IN_WAKEUP;
wake_up_process(q->sleeper); /* doesn't sleep */
smp_wmb();
q->status = -EIDRM; /* hands-off q */
- q = n;
}
/* Remove the semaphore set from the IDR */
}
}
-static int semctl_nolock(struct ipc_namespace *ns, int semid, int semnum,
- int cmd, int version, union semun arg)
+static int semctl_nolock(struct ipc_namespace *ns, int semid,
+ int cmd, int version, union semun arg)
{
int err = -EINVAL;
struct sem_array *sma;
return -EFAULT;
return (max_id < 0) ? 0: max_id;
}
+ case IPC_STAT:
case SEM_STAT:
{
struct semid64_ds tbuf;
int id;
- sma = sem_lock(ns, semid);
- if (IS_ERR(sma))
- return PTR_ERR(sma);
+ if (cmd == SEM_STAT) {
+ sma = sem_lock(ns, semid);
+ if (IS_ERR(sma))
+ return PTR_ERR(sma);
+ id = sma->sem_perm.id;
+ } else {
+ sma = sem_lock_check(ns, semid);
+ if (IS_ERR(sma))
+ return PTR_ERR(sma);
+ id = 0;
+ }
err = -EACCES;
if (ipcperms (&sma->sem_perm, S_IRUGO))
if (err)
goto out_unlock;
- id = sma->sem_perm.id;
-
memset(&tbuf, 0, sizeof(tbuf));
kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
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);
err = 0;
goto out_unlock;
}
- case IPC_STAT:
- {
- struct semid64_ds tbuf;
- memset(&tbuf,0,sizeof(tbuf));
- kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
- tbuf.sem_otime = sma->sem_otime;
- tbuf.sem_ctime = sma->sem_ctime;
- tbuf.sem_nsems = sma->sem_nsems;
- sem_unlock(sma);
- if (copy_semid_to_user (arg.buf, &tbuf, version))
- return -EFAULT;
- return 0;
- }
/* GETVAL, GETPID, GETNCTN, GETZCNT, SETVAL: fall-through */
}
err = -EINVAL;
{
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();
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, sma);
- err = 0;
- break;
+ freeary(ns, ipcp);
+ 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;
switch(cmd) {
case IPC_INFO:
case SEM_INFO:
+ case IPC_STAT:
case SEM_STAT:
- err = semctl_nolock(ns,semid,semnum,cmd,version,arg);
+ err = semctl_nolock(ns, semid, cmd, version, arg);
return err;
case GETALL:
case GETVAL:
case GETPID:
case GETNCNT:
case GETZCNT:
- case IPC_STAT:
case SETVAL:
case SETALL:
err = semctl_main(ns,semid,semnum,cmd,version,arg);
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;
static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
{
- struct sem_undo **last, *un;
+ struct sem_undo *walk;
- 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;
+ list_for_each_entry_rcu(walk, &ulp->list_proc, list_proc) {
+ if (walk->semid == semid)
+ return walk;
}
- return un;
+ return NULL;
}
-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;
* 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);
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;
+ list_del(&queue.list);
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_dereference(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:
sem_unlock(sma);
+
+ call_rcu(&un->rcu, free_un);
}
- kfree(undo_list);
+ kfree(ulp);
}
#ifdef CONFIG_PROC_FS
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff