ipc/sem.c: remove unused entries from struct sem_queue
[safe/jmp/linux-2.6] / ipc / sem.c
index 40ab34d..d5ce400 100644 (file)
--- a/ipc/sem.c
+++ b/ipc/sem.c
 #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
@@ -117,74 +115,32 @@ static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
 #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.
  */
@@ -192,6 +148,9 @@ static inline struct sem_array *sem_lock(struct ipc_namespace *ns, int id)
 {
        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);
 }
 
@@ -200,9 +159,31 @@ static inline struct sem_array *sem_lock_check(struct ipc_namespace *ns,
 {
        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);
@@ -283,18 +264,17 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
        }
 
        id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
-       if(id == -1) {
+       if (id < 0) {
                security_sem_free(sma);
                ipc_rcu_putref(sma);
-               return -ENOSPC;
+               return id;
        }
        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->list_id);
        sma->sem_nsems = nsems;
        sma->sem_ctime = get_seconds();
        sem_unlock(sma);
@@ -546,16 +526,18 @@ static int count_semzcnt (struct sem_array * sma, ushort semnum)
  * 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;
+       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)
+       assert_spin_locked(&sma->sem_perm.lock);
+       list_for_each_entry(un, &sma->list_id, list_id)
                un->semid = -1;
 
        /* Wake up all pending processes and let them fail with EIDRM. */
@@ -603,8 +585,8 @@ static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in,
        }
 }
 
-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;
@@ -643,14 +625,23 @@ static int semctl_nolock(struct ipc_namespace *ns, int semid, int semnum,
                        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))
@@ -660,8 +651,6 @@ static int semctl_nolock(struct ipc_namespace *ns, int semid, int semnum,
                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);
@@ -714,19 +703,15 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
                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;
@@ -747,38 +732,30 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
                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;
@@ -787,28 +764,18 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
 
                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;
@@ -834,12 +801,15 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
        {
                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();
@@ -857,28 +827,14 @@ out_free:
        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;
@@ -886,9 +842,9 @@ static inline unsigned long copy_semid_from_user(struct sem_setbuf *out, void __
                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;
            }
@@ -897,38 +853,29 @@ static inline unsigned long copy_semid_from_user(struct sem_setbuf *out, void __
        }
 }
 
-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;
+       ipcp = ipcctl_pre_down(&sem_ids(ns), semid, cmd, &semid64.sem_perm, 0);
+       if (IS_ERR(ipcp))
+               return PTR_ERR(ipcp);
 
-       err = audit_ipc_obj(ipcp);
-       if (err)
-               goto out_unlock;
-
-       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)
@@ -936,27 +883,20 @@ static int semctl_down(struct ipc_namespace *ns, int semid, int semnum,
 
        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;
 }
 
@@ -975,60 +915,28 @@ asmlinkage long sys_semctl (int semid, int semnum, int cmd, union semun arg)
        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;
        }
 }
 
-static inline void lock_semundo(void)
-{
-       struct sem_undo_list *undo_list;
-
-       undo_list = current->sysvsem.undo_list;
-       if (undo_list)
-               spin_lock(&undo_list->lock);
-}
-
-/* This code has an interaction with copy_semundo().
- * Consider; two tasks are sharing the undo_list. task1
- * acquires the undo_list lock in lock_semundo().  If task2 now
- * exits before task1 releases the lock (by calling
- * unlock_semundo()), then task1 will never call spin_unlock().
- * This leave the sem_undo_list in a locked state.  If task1 now creats task3
- * and once again shares the sem_undo_list, the sem_undo_list will still be
- * locked, and future SEM_UNDO operations will deadlock.  This case is
- * dealt with in copy_semundo() by having it reinitialize the spin lock when 
- * the refcnt goes from 1 to 2.
- */
-static inline void unlock_semundo(void)
-{
-       struct sem_undo_list *undo_list;
-
-       undo_list = current->sysvsem.undo_list;
-       if (undo_list)
-               spin_unlock(&undo_list->lock);
-}
-
-
 /* 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,
  * and current is THE ONE
@@ -1051,6 +959,8 @@ static inline int get_undo_list(struct sem_undo_list **undo_listp)
                        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;
@@ -1059,25 +969,30 @@ static inline int get_undo_list(struct sem_undo_list **undo_listp)
 
 static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
 {
-       struct sem_undo **last, *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;
+       struct sem_undo *walk, *tmp;
+
+       assert_spin_locked(&ulp->lock);
+       list_for_each_entry_safe(walk, tmp, &ulp->list_proc, list_proc) {
+               if (walk->semid == semid)
+                       return walk;
+               if (walk->semid == -1) {
+                       list_del(&walk->list_proc);
+                       kfree(walk);
                }
-               un=*last;
        }
-       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.
+ */
+static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
 {
        struct sem_array *sma;
        struct sem_undo_list *ulp;
@@ -1089,57 +1004,60 @@ static struct sem_undo *find_undo(struct ipc_namespace *ns, int semid)
        if (error)
                return ERR_PTR(error);
 
-       lock_semundo();
+       spin_lock(&ulp->lock);
        un = lookup_undo(ulp, semid);
-       unlock_semundo();
+       spin_unlock(&ulp->lock);
        if (likely(un!=NULL))
                goto out;
 
        /* 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;
 
-       lock_semundo();
+       /* step 3: Acquire the lock on the undo list pointer */
+       spin_lock(&ulp->lock);
+
+       /* step 4: check for races: someone else allocated the undo struct,
+        *         semaphore array was destroyed.
+        */
        un = lookup_undo(ulp, semid);
        if (un) {
-               unlock_semundo();
+               spin_unlock(&ulp->lock);
                kfree(new);
-               ipc_lock_by_ptr(&sma->sem_perm);
-               ipc_rcu_putref(sma);
-               sem_unlock(sma);
+               sem_putref(sma);
                goto out;
        }
-       ipc_lock_by_ptr(&sma->sem_perm);
-       ipc_rcu_putref(sma);
+       sem_lock_and_putref(sma);
        if (sma->sem_perm.deleted) {
                sem_unlock(sma);
-               unlock_semundo();
+               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;
+       /* step 5: initialize & link new undo structure */
+       new->semadj = (short *) &new[1];
+       new->semid = semid;
+       assert_spin_locked(&ulp->lock);
+       list_add(&new->list_proc, &ulp->list_proc);
+       assert_spin_locked(&sma->sem_perm.lock);
+       list_add(&new->list_id, &sma->list_id);
+
        sem_unlock(sma);
+       spin_unlock(&ulp->lock);
        un = new;
-       unlock_semundo();
 out:
        return un;
 }
@@ -1195,9 +1113,8 @@ asmlinkage long sys_semtimedop(int semid, struct sembuf __user *tsops,
                        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;
@@ -1212,14 +1129,14 @@ retry_undos:
        }
 
        /*
-        * 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.
         */
-       if (un && un->semid == -1) {
-               sem_unlock(sma);
-               goto retry_undos;
-       }
+       error = -EIDRM;
+       if (un && un->semid == -1)
+               goto out_unlock_free;
+
        error = -EFBIG;
        if (max >= sma->sem_nsems)
                goto out_unlock_free;
@@ -1243,12 +1160,10 @@ retry_undos:
         * 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);
@@ -1315,10 +1230,6 @@ asmlinkage long sys_semop (int semid, struct sembuf __user *tsops, unsigned nsop
 
 /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
  * parent and child tasks.
- *
- * See the notes above unlock_semundo() regarding the spin_lock_init()
- * in this code.  Initialize the undo_list->lock here instead of get_undo_list()
- * because of the reasoning in the comment above unlock_semundo.
  */
 
 int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
@@ -1352,55 +1263,44 @@ int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
  */
 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;
+       struct sem_undo *un, *tmp;
 
-       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)) {
+       spin_lock(&ulp->lock);
+
+       list_for_each_entry_safe(un, tmp, &ulp->list_proc, list_proc) {
                struct sem_array *sma;
-               int nsems, i;
-               struct sem_undo *un, **unp;
-               int semid;
-              
-               semid = u->semid;
-
-               if(semid == -1)
-                       continue;
-               sma = sem_lock(ns, semid);
+               int i;
+
+               if (un->semid == -1)
+                       goto free;
+
+               sma = sem_lock(tsk->nsproxy->ipc_ns, un->semid);
                if (IS_ERR(sma))
-                       continue;
+                       goto free;
 
-               if (u->semid == -1)
-                       goto next_entry;
+               if (un->semid == -1)
+                       goto unlock_free;
 
-               BUG_ON(sem_checkid(sma, u->semid));
+               BUG_ON(sem_checkid(sma, un->semid));
 
-               /* 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++) {
+               /* remove un from sma->list_id */
+               assert_spin_locked(&sma->sem_perm.lock);
+               list_del(&un->list_id);
+
+               /* 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:
@@ -1424,10 +1324,15 @@ found:
                sma->sem_otime = get_seconds();
                /* maybe some queued-up processes were waiting for this */
                update_queue(sma);
-next_entry:
+unlock_free:
                sem_unlock(sma);
+free:
+               assert_spin_locked(&ulp->lock);
+               list_del(&un->list_proc);
+               kfree(un);
        }
-       kfree(undo_list);
+       spin_unlock(&ulp->lock);
+       kfree(ulp);
 }
 
 #ifdef CONFIG_PROC_FS