ipc/sem.c: convert sem_array.sem_pending to struct list_head
sem_array.sem_pending is a double linked list, the attached patch converts it to struct list_head. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Manfred Spraul <manfred@colorfullife.com> Reviewed-by: 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>
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@ -93,21 +93,19 @@ struct sem_array {
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time_t sem_otime; /* last semop time */
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time_t sem_ctime; /* last change time */
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struct sem *sem_base; /* ptr to first semaphore in array */
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struct sem_queue *sem_pending; /* pending operations to be processed */
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struct sem_queue **sem_pending_last; /* last pending operation */
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struct list_head sem_pending; /* pending operations to be processed */
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struct list_head list_id; /* undo requests on this array */
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unsigned long sem_nsems; /* no. of semaphores in array */
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};
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/* One queue for each sleeping process in the system. */
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struct sem_queue {
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struct sem_queue * next; /* next entry in the queue */
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struct sem_queue ** prev; /* previous entry in the queue, *(q->prev) == q */
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struct task_struct* sleeper; /* this process */
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struct sem_undo * undo; /* undo structure */
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struct list_head list; /* queue of pending operations */
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struct task_struct *sleeper; /* this process */
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struct sem_undo *undo; /* undo structure */
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int pid; /* process id of requesting process */
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int status; /* completion status of operation */
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struct sembuf * sops; /* array of pending operations */
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struct sembuf *sops; /* array of pending operations */
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int nsops; /* number of operations */
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int alter; /* does the operation alter the array? */
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};
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92
ipc/sem.c
92
ipc/sem.c
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@ -272,8 +272,7 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
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ns->used_sems += nsems;
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sma->sem_base = (struct sem *) &sma[1];
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/* sma->sem_pending = NULL; */
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sma->sem_pending_last = &sma->sem_pending;
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INIT_LIST_HEAD(&sma->sem_pending);
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INIT_LIST_HEAD(&sma->list_id);
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sma->sem_nsems = nsems;
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sma->sem_ctime = get_seconds();
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@ -331,38 +330,6 @@ asmlinkage long sys_semget(key_t key, int nsems, int semflg)
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return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
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}
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/* Manage the doubly linked list sma->sem_pending as a FIFO:
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* insert new queue elements at the tail sma->sem_pending_last.
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*/
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static inline void append_to_queue (struct sem_array * sma,
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struct sem_queue * q)
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{
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*(q->prev = sma->sem_pending_last) = q;
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*(sma->sem_pending_last = &q->next) = NULL;
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}
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static inline void prepend_to_queue (struct sem_array * sma,
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struct sem_queue * q)
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{
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q->next = sma->sem_pending;
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*(q->prev = &sma->sem_pending) = q;
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if (q->next)
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q->next->prev = &q->next;
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else /* sma->sem_pending_last == &sma->sem_pending */
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sma->sem_pending_last = &q->next;
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}
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static inline void remove_from_queue (struct sem_array * sma,
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struct sem_queue * q)
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{
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*(q->prev) = q->next;
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if (q->next)
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q->next->prev = q->prev;
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else /* sma->sem_pending_last == &q->next */
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sma->sem_pending_last = q->prev;
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q->prev = NULL; /* mark as removed */
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}
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/*
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* Determine whether a sequence of semaphore operations would succeed
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* all at once. Return 0 if yes, 1 if need to sleep, else return error code.
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@ -438,16 +405,15 @@ static void update_queue (struct sem_array * sma)
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int error;
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struct sem_queue * q;
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q = sma->sem_pending;
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while(q) {
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q = list_entry(sma->sem_pending.next, struct sem_queue, list);
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while (&q->list != &sma->sem_pending) {
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error = try_atomic_semop(sma, q->sops, q->nsops,
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q->undo, q->pid);
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/* Does q->sleeper still need to sleep? */
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if (error <= 0) {
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struct sem_queue *n;
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remove_from_queue(sma,q);
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q->status = IN_WAKEUP;
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/*
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* Continue scanning. The next operation
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* that must be checked depends on the type of the
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@ -458,11 +424,26 @@ static void update_queue (struct sem_array * sma)
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* for semaphore values to become 0.
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* - if the operation didn't modify the array,
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* then just continue.
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* The order of list_del() and reading ->next
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* is crucial: In the former case, the list_del()
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* must be done first [because we might be the
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* first entry in ->sem_pending], in the latter
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* case the list_del() must be done last
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* [because the list is invalid after the list_del()]
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*/
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if (q->alter)
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n = sma->sem_pending;
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else
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n = q->next;
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if (q->alter) {
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list_del(&q->list);
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n = list_entry(sma->sem_pending.next,
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struct sem_queue, list);
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} else {
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n = list_entry(q->list.next, struct sem_queue,
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list);
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list_del(&q->list);
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}
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/* wake up the waiting thread */
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q->status = IN_WAKEUP;
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wake_up_process(q->sleeper);
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/* hands-off: q will disappear immediately after
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* writing q->status.
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@ -471,7 +452,7 @@ static void update_queue (struct sem_array * sma)
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q->status = error;
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q = n;
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} else {
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q = q->next;
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q = list_entry(q->list.next, struct sem_queue, list);
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}
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}
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}
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@ -491,7 +472,7 @@ static int count_semncnt (struct sem_array * sma, ushort semnum)
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struct sem_queue * q;
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semncnt = 0;
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for (q = sma->sem_pending; q; q = q->next) {
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list_for_each_entry(q, &sma->sem_pending, list) {
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struct sembuf * sops = q->sops;
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int nsops = q->nsops;
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int i;
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@ -503,13 +484,14 @@ static int count_semncnt (struct sem_array * sma, ushort semnum)
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}
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return semncnt;
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}
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static int count_semzcnt (struct sem_array * sma, ushort semnum)
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{
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int semzcnt;
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struct sem_queue * q;
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semzcnt = 0;
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for (q = sma->sem_pending; q; q = q->next) {
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list_for_each_entry(q, &sma->sem_pending, list) {
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struct sembuf * sops = q->sops;
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int nsops = q->nsops;
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int i;
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@ -529,7 +511,7 @@ static int count_semzcnt (struct sem_array * sma, ushort semnum)
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static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
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{
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struct sem_undo *un;
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struct sem_queue *q;
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struct sem_queue *q, *t;
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struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
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/* Invalidate the existing undo structures for this semaphore set.
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@ -541,17 +523,14 @@ static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
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un->semid = -1;
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/* Wake up all pending processes and let them fail with EIDRM. */
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q = sma->sem_pending;
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while(q) {
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struct sem_queue *n;
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/* lazy remove_from_queue: we are killing the whole queue */
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q->prev = NULL;
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n = q->next;
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list_for_each_entry_safe(q, t, &sma->sem_pending, list) {
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list_del(&q->list);
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q->status = IN_WAKEUP;
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wake_up_process(q->sleeper); /* doesn't sleep */
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smp_wmb();
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q->status = -EIDRM; /* hands-off q */
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q = n;
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}
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/* Remove the semaphore set from the IDR */
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@ -1166,9 +1145,9 @@ asmlinkage long sys_semtimedop(int semid, struct sembuf __user *tsops,
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queue.pid = task_tgid_vnr(current);
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queue.alter = alter;
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if (alter)
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append_to_queue(sma ,&queue);
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list_add_tail(&queue.list, &sma->sem_pending);
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else
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prepend_to_queue(sma ,&queue);
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list_add(&queue.list, &sma->sem_pending);
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queue.status = -EINTR;
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queue.sleeper = current;
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@ -1194,7 +1173,6 @@ asmlinkage long sys_semtimedop(int semid, struct sembuf __user *tsops,
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sma = sem_lock(ns, semid);
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if (IS_ERR(sma)) {
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BUG_ON(queue.prev != NULL);
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error = -EIDRM;
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goto out_free;
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}
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@ -1212,7 +1190,7 @@ asmlinkage long sys_semtimedop(int semid, struct sembuf __user *tsops,
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*/
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if (timeout && jiffies_left == 0)
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error = -EAGAIN;
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remove_from_queue(sma,&queue);
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list_del(&queue.list);
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goto out_unlock_free;
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out_unlock_free:
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