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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.

[[email protected]: coding-style fixes]
Signed-off-by: Manfred Spraul <[email protected]>
Cc: Nadia Derbey <[email protected]>
Cc: Pierre Peiffer <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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@manfred-colorfu @torvalds
manfred-colorfu authored and torvalds committed Jul 25, 2008
1 parent 00c2bf8 commit 4daa28f
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Showing 2 changed files with 95 additions and 80 deletions.
12 changes: 6 additions & 6 deletions include/linux/sem.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -95,7 +95,7 @@ struct sem_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_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 */
};

Expand All @@ -118,8 +118,8 @@ struct sem_queue {
* when the process exits.
*/
struct sem_undo {
struct sem_undo * proc_next; /* next entry on this process */
struct sem_undo * id_next; /* next entry on this semaphore set */
struct list_head list_proc; /* per-process list: all undos from one process */
struct list_head list_id; /* per semaphore array list: all undos for one array */
int semid; /* semaphore set identifier */
short * semadj; /* array of adjustments, one per semaphore */
};
Expand All @@ -128,9 +128,9 @@ struct sem_undo {
* that may be shared among all a CLONE_SYSVSEM task group.
*/
struct sem_undo_list {
atomic_t refcnt;
spinlock_t lock;
struct sem_undo *proc_list;
atomic_t refcnt;
spinlock_t lock;
struct list_head list_proc;
};

struct sysv_sem {
Expand Down
163 changes: 89 additions & 74 deletions ipc/sem.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -274,7 +274,7 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
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);
Expand Down Expand Up @@ -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()
* 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. */
Expand Down Expand Up @@ -763,9 +764,12 @@ 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);
Expand Down Expand Up @@ -797,12 +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();
Expand Down Expand Up @@ -952,6 +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;
Expand All @@ -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)
{
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;
Expand All @@ -997,22 +1011,27 @@ static struct sem_undo *find_undo(struct ipc_namespace *ns, int semid)
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;
sem_getref_and_unlock(sma);

/* step 2: allocate new undo structure */
new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
if (!new) {
sem_putref(sma);
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);

/* step 4: check for races: someone else allocated the undo struct,
* semaphore array was destroyed.
*/
un = lookup_undo(ulp, semid);
if (un) {
spin_unlock(&ulp->lock);
Expand All @@ -1028,13 +1047,17 @@ static struct sem_undo *find_undo(struct ipc_namespace *ns, int semid)
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);
un = new;
spin_unlock(&ulp->lock);
un = new;
out:
return un;
}
Expand Down Expand Up @@ -1090,9 +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;
Expand All @@ -1107,14 +1129,14 @@ asmlinkage long sys_semtimedop(int semid, struct sembuf __user *tsops,
}

/*
* 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;
Expand Down Expand Up @@ -1243,56 +1265,44 @@ 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:
Expand All @@ -1316,10 +1326,15 @@ void exit_sem(struct task_struct *tsk)
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
Expand Down

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