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ipc/sem.c: convert undo structures to struct list_head

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The undo structures contain two linked lists, the attached patch replaces
them with generic struct list_head lists.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Cc: Pierre Peiffer <peifferp@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Manfred Spraul 2008-07-25 01:48:04 -07:00 • committed by Linus Torvalds
parent 00c2bf85d8
commit 4daa28f6d8
2 changed files with 93 additions and 78 deletions
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12
include/linux/sem.h
View file

@ -95,7 +95,7 @@ struct sem_array {
struct sem *sem_base; /* ptr to first semaphore in array */ struct sem *sem_base; /* ptr to first semaphore in array */
struct sem_queue *sem_pending; /* pending operations to be processed */ struct sem_queue *sem_pending; /* pending operations to be processed */
struct sem_queue **sem_pending_last; /* last pending operation */ struct sem_queue **sem_pending_last; /* last pending operation */
struct sem_undo *undo; /* undo requests on this array */ struct list_head list_id; /* undo requests on this array */
unsigned long sem_nsems; /* no. of semaphores in array */ unsigned long sem_nsems; /* no. of semaphores in array */
}; };
@ -118,8 +118,8 @@ struct sem_queue {
* when the process exits. * when the process exits.
*/ */
struct sem_undo { struct sem_undo {
struct sem_undo * proc_next; /* next entry on this process */ struct list_head list_proc; /* per-process list: all undos from one process */
struct sem_undo * id_next; /* next entry on this semaphore set */ struct list_head list_id; /* per semaphore array list: all undos for one array */
int semid; /* semaphore set identifier */ int semid; /* semaphore set identifier */
short * semadj; /* array of adjustments, one per semaphore */ short * semadj; /* array of adjustments, one per semaphore */
}; };
@ -128,9 +128,9 @@ struct sem_undo {
* that may be shared among all a CLONE_SYSVSEM task group. * that may be shared among all a CLONE_SYSVSEM task group.
*/ */
struct sem_undo_list { struct sem_undo_list {
atomic_t refcnt; atomic_t refcnt;
spinlock_t lock; spinlock_t lock;
struct sem_undo *proc_list; struct list_head list_proc;
}; };
struct sysv_sem { struct sysv_sem {

157
ipc/sem.c
View file

@ -274,7 +274,7 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
sma->sem_base = (struct sem *) &sma[1]; sma->sem_base = (struct sem *) &sma[1];
/* sma->sem_pending = NULL; */ /* sma->sem_pending = NULL; */
sma->sem_pending_last = &sma->sem_pending; sma->sem_pending_last = &sma->sem_pending;
/* sma->undo = NULL; */ INIT_LIST_HEAD(&sma->list_id);
sma->sem_nsems = nsems; sma->sem_nsems = nsems;
sma->sem_ctime = get_seconds(); sma->sem_ctime = get_seconds();
sem_unlock(sma); sem_unlock(sma);
@ -536,7 +536,8 @@ static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
* (They will be freed without any further action in exit_sem() * (They will be freed without any further action in exit_sem()
* or during the next semop.) * 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; un->semid = -1;
/* Wake up all pending processes and let them fail with EIDRM. */ /* Wake up all pending processes and let them fail with EIDRM. */
@ -763,9 +764,12 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
for (i = 0; i < nsems; i++) for (i = 0; i < nsems; i++)
sma->sem_base[i].semval = sem_io[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++) for (i = 0; i < nsems; i++)
un->semadj[i] = 0; un->semadj[i] = 0;
}
sma->sem_ctime = get_seconds(); sma->sem_ctime = get_seconds();
/* maybe some queued-up processes were waiting for this */ /* maybe some queued-up processes were waiting for this */
update_queue(sma); update_queue(sma);
@ -797,12 +801,15 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
{ {
int val = arg.val; int val = arg.val;
struct sem_undo *un; struct sem_undo *un;
err = -ERANGE; err = -ERANGE;
if (val > SEMVMX || val < 0) if (val > SEMVMX || val < 0)
goto out_unlock; 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; un->semadj[semnum] = 0;
curr->semval = val; curr->semval = val;
curr->sempid = task_tgid_vnr(current); curr->sempid = task_tgid_vnr(current);
sma->sem_ctime = get_seconds(); sma->sem_ctime = get_seconds();
@ -952,6 +959,8 @@ static inline int get_undo_list(struct sem_undo_list **undo_listp)
return -ENOMEM; return -ENOMEM;
spin_lock_init(&undo_list->lock); spin_lock_init(&undo_list->lock);
atomic_set(&undo_list->refcnt, 1); atomic_set(&undo_list->refcnt, 1);
INIT_LIST_HEAD(&undo_list->list_proc);
current->sysvsem.undo_list = undo_list; current->sysvsem.undo_list = undo_list;
} }
*undo_listp = undo_list; *undo_listp = undo_list;
@ -960,25 +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) static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
{ {
struct sem_undo **last, *un; struct sem_undo *walk, *tmp;
last = &ulp->proc_list; assert_spin_locked(&ulp->lock);
un = *last; list_for_each_entry_safe(walk, tmp, &ulp->list_proc, list_proc) {
while(un != NULL) { if (walk->semid == semid)
if(un->semid==semid) return walk;
break; if (walk->semid == -1) {
if(un->semid==-1) { list_del(&walk->list_proc);
*last=un->proc_next; kfree(walk);
kfree(un);
} else {
last=&un->proc_next;
} }
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_array *sma;
struct sem_undo_list *ulp; struct sem_undo_list *ulp;
@ -997,6 +1011,7 @@ static struct sem_undo *find_undo(struct ipc_namespace *ns, int semid)
goto out; goto out;
/* no undo structure around - allocate one. */ /* no undo structure around - allocate one. */
/* step 1: figure out the size of the semaphore array */
sma = sem_lock_check(ns, semid); sma = sem_lock_check(ns, semid);
if (IS_ERR(sma)) if (IS_ERR(sma))
return ERR_PTR(PTR_ERR(sma)); return ERR_PTR(PTR_ERR(sma));
@ -1004,15 +1019,19 @@ static struct sem_undo *find_undo(struct ipc_namespace *ns, int semid)
nsems = sma->sem_nsems; nsems = sma->sem_nsems;
sem_getref_and_unlock(sma); sem_getref_and_unlock(sma);
/* step 2: allocate new undo structure */
new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL); new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
if (!new) { if (!new) {
sem_putref(sma); sem_putref(sma);
return ERR_PTR(-ENOMEM); return ERR_PTR(-ENOMEM);
} }
new->semadj = (short *) &new[1];
new->semid = semid;
/* step 3: Acquire the lock on the undo list pointer */
spin_lock(&ulp->lock); spin_lock(&ulp->lock);
/* step 4: check for races: someone else allocated the undo struct,
* semaphore array was destroyed.
*/
un = lookup_undo(ulp, semid); un = lookup_undo(ulp, semid);
if (un) { if (un) {
spin_unlock(&ulp->lock); spin_unlock(&ulp->lock);
@ -1028,13 +1047,17 @@ static struct sem_undo *find_undo(struct ipc_namespace *ns, int semid)
un = ERR_PTR(-EIDRM); un = ERR_PTR(-EIDRM);
goto out; goto out;
} }
new->proc_next = ulp->proc_list; /* step 5: initialize & link new undo structure */
ulp->proc_list = new; new->semadj = (short *) &new[1];
new->id_next = sma->undo; new->semid = semid;
sma->undo = new; 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); sem_unlock(sma);
un = new;
spin_unlock(&ulp->lock); spin_unlock(&ulp->lock);
un = new;
out: out:
return un; return un;
} }
@ -1090,9 +1113,8 @@ asmlinkage long sys_semtimedop(int semid, struct sembuf __user *tsops,
alter = 1; alter = 1;
} }
retry_undos:
if (undos) { if (undos) {
un = find_undo(ns, semid); un = find_alloc_undo(ns, semid);
if (IS_ERR(un)) { if (IS_ERR(un)) {
error = PTR_ERR(un); error = PTR_ERR(un);
goto out_free; goto out_free;
@ -1107,14 +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 * 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) { error = -EIDRM;
sem_unlock(sma); if (un && un->semid == -1)
goto retry_undos; goto out_unlock_free;
}
error = -EFBIG; error = -EFBIG;
if (max >= sma->sem_nsems) if (max >= sma->sem_nsems)
goto out_unlock_free; goto out_unlock_free;
@ -1243,56 +1265,44 @@ int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
*/ */
void exit_sem(struct task_struct *tsk) void exit_sem(struct task_struct *tsk)
{ {
struct sem_undo_list *undo_list; struct sem_undo_list *ulp;
struct sem_undo *u, **up; struct sem_undo *un, *tmp;
struct ipc_namespace *ns;
undo_list = tsk->sysvsem.undo_list; ulp = tsk->sysvsem.undo_list;
if (!undo_list) if (!ulp)
return; return;
tsk->sysvsem.undo_list = NULL; tsk->sysvsem.undo_list = NULL;
if (!atomic_dec_and_test(&undo_list->refcnt)) if (!atomic_dec_and_test(&ulp->refcnt))
return; return;
ns = tsk->nsproxy->ipc_ns; spin_lock(&ulp->lock);
/* There's no need to hold the semundo list lock, as current
* is the last task exiting for this undo list. list_for_each_entry_safe(un, tmp, &ulp->list_proc, list_proc) {
*/
for (up = &undo_list->proc_list; (u = *up); *up = u->proc_next, kfree(u)) {
struct sem_array *sma; struct sem_array *sma;
int nsems, i; int i;
struct sem_undo *un, **unp;
int semid;
semid = u->semid; if (un->semid == -1)
goto free;
if(semid == -1) sma = sem_lock(tsk->nsproxy->ipc_ns, un->semid);
continue;
sma = sem_lock(ns, semid);
if (IS_ERR(sma)) if (IS_ERR(sma))
continue; goto free;
if (u->semid == -1) if (un->semid == -1)
goto next_entry; goto unlock_free;
BUG_ON(sem_checkid(sma, u->semid)); BUG_ON(sem_checkid(sma, un->semid));
/* remove u from the sma->undo list */ /* remove un from sma->list_id */
for (unp = &sma->undo; (un = *unp); unp = &un->id_next) { assert_spin_locked(&sma->sem_perm.lock);
if (u == un) list_del(&un->list_id);
goto found;
} /* perform adjustments registered in un */
printk ("exit_sem undo list error id=%d\n", u->semid); for (i = 0; i < sma->sem_nsems; i++) {
goto next_entry;
found:
*unp = un->id_next;
/* perform adjustments registered in u */
nsems = sma->sem_nsems;
for (i = 0; i < nsems; i++) {
struct sem * semaphore = &sma->sem_base[i]; struct sem * semaphore = &sma->sem_base[i];
if (u->semadj[i]) { if (un->semadj[i]) {
semaphore->semval += u->semadj[i]; semaphore->semval += un->semadj[i];
/* /*
* Range checks of the new semaphore value, * Range checks of the new semaphore value,
* not defined by sus: * not defined by sus:
@ -1316,10 +1326,15 @@ found:
sma->sem_otime = get_seconds(); sma->sem_otime = get_seconds();
/* maybe some queued-up processes were waiting for this */ /* maybe some queued-up processes were waiting for this */
update_queue(sma); update_queue(sma);
next_entry: unlock_free:
sem_unlock(sma); 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 #ifdef CONFIG_PROC_FS