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diff --git a/src/clnt_fd_locks.h b/src/clnt_fd_locks.h
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+/*
+ * debug.h -- debugging routines for libtirpc
+ *
+ * Copyright (c) 2020 SUSE LINUX GmbH, Nuernberg, Germany.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * - Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.
+ * - Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ * - Neither the name of Sun Microsystems, Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _CLNT_FD_LOCKS_H
+#define _CLNT_FD_LOCKS_H
+
+#include <sys/queue.h>
+#include <errno.h>
+#include <reentrant.h>
+#include <rpc/xdr.h>
+
+
+/*
+ * This utility manages a list of per-fd locks for the clients.
+ *
+ * If MAX_FDLOCKS_PREALLOC is defined, a number of pre-fd locks will be
+ * pre-allocated. This number is the minimum of MAX_FDLOCKS_PREALLOC or
+ * the process soft limit of allowed fds.
+ */
+#ifdef MAX_FDLOCKS_PREALLOC
+static unsigned int fd_locks_prealloc = 0;
+#endif
+
+/* per-fd lock */
+struct fd_lock_t {
+ bool_t active;
+ int pending; /* Number of pending operations on fd */
+ cond_t cv;
+};
+typedef struct fd_lock_t fd_lock_t;
+
+
+/* internal type to store per-fd locks in a list */
+struct fd_lock_item_t {
+ /* fd_lock_t first so we can cast to fd_lock_item_t */
+ fd_lock_t fd_lock;
+ int fd;
+ unsigned int refs;
+ TAILQ_ENTRY(fd_lock_item_t) link;
+};
+typedef struct fd_lock_item_t fd_lock_item_t;
+#define to_fd_lock_item(fdlock_t_ptr) ((fd_lock_item_t*) fdlock_t_ptr)
+
+
+/* internal list of per-fd locks */
+typedef TAILQ_HEAD(,fd_lock_item_t) fd_lock_list_t;
+
+
+#ifdef MAX_FDLOCKS_PREALLOC
+
+/* With pre-allocation, keep track of both an array and a list */
+struct fd_locks_t {
+ fd_lock_list_t fd_lock_list;
+ fd_lock_t *fd_lock_array;
+};
+typedef struct fd_locks_t fd_locks_t;
+#define to_fd_lock_list(fd_locks_t_ptr) (&fd_locks_t_ptr->fd_lock_list)
+
+#else
+
+/* With no pre-allocation, just keep track of a list */
+typedef fd_lock_list_t fd_locks_t;
+#define to_fd_lock_list(fd_locks_t_ptr) ((fd_lock_list_t *) fd_locks_t_ptr)
+
+#endif
+
+
+/* allocate fd locks */
+static inline
+fd_locks_t* fd_locks_init() {
+ fd_locks_t *fd_locks;
+
+ fd_locks = (fd_locks_t *) mem_alloc(sizeof(fd_locks_t));
+ if (fd_locks == (fd_locks_t *) NULL) {
+ errno = ENOMEM;
+ return (NULL);
+ }
+ TAILQ_INIT(to_fd_lock_list(fd_locks));
+
+#ifdef MAX_FDLOCKS_PREALLOC
+ size_t fd_lock_arraysz;
+
+ if (fd_locks_prealloc == 0) {
+ unsigned int dtbsize = __rpc_dtbsize();
+ if (0 < dtbsize && dtbsize < MAX_FDLOCKS_PREALLOC)
+ fd_locks_prealloc = dtbsize;
+ else
+ fd_locks_prealloc = MAX_FDLOCKS_PREALLOC;
+ }
+
+ if ( (size_t) fd_locks_prealloc > SIZE_MAX/sizeof(fd_lock_t)) {
+ mem_free(fd_locks, sizeof (*fd_locks));
+ errno = EOVERFLOW;
+ return (NULL);
+ }
+
+ fd_lock_arraysz = fd_locks_prealloc * sizeof (fd_lock_t);
+ fd_locks->fd_lock_array = (fd_lock_t *) mem_alloc(fd_lock_arraysz);
+ if (fd_locks->fd_lock_array == (fd_lock_t *) NULL) {
+ mem_free(fd_locks, sizeof (*fd_locks));
+ errno = ENOMEM;
+ return (NULL);
+ }
+ else {
+ int i;
+
+ for (i = 0; i < fd_locks_prealloc; i++) {
+ fd_locks->fd_lock_array[i].active = FALSE;
+ cond_init(&fd_locks->fd_lock_array[i].cv, 0, (void *) 0);
+ }
+ }
+#endif
+
+ return fd_locks;
+}
+
+/* de-allocate fd locks */
+static inline
+void fd_locks_destroy(fd_locks_t *fd_locks) {
+#ifdef MAX_FDLOCKS_PREALLOC
+ fd_lock_t *array = fd_locks->fd_lock_array;
+ mem_free(array, fd_locks_prealloc * sizeof (fd_lock_t));
+#endif
+ fd_lock_item_t *item;
+ fd_lock_list_t *list = to_fd_lock_list(fd_locks);
+
+ TAILQ_FOREACH(item, list, link) {
+ cond_destroy(&item->fd_lock.cv);
+ mem_free(item, sizeof (*item));
+ }
+ mem_free(fd_locks, sizeof (*fd_locks));
+}
+
+/* allocate per-fd lock */
+static inline
+fd_lock_t* fd_lock_create(int fd, fd_locks_t *fd_locks) {
+#ifdef MAX_FDLOCKS_PREALLOC
+ if (fd < fd_locks_prealloc) {
+ return &fd_locks->fd_lock_array[fd];
+ }
+#endif
+ fd_lock_item_t *item;
+ fd_lock_list_t *list = to_fd_lock_list(fd_locks);
+
+ for (item = TAILQ_FIRST(list);
+ item != (fd_lock_item_t *) NULL && item->fd != fd;
+ item = TAILQ_NEXT(item, link));
+
+ if (item == (fd_lock_item_t *) NULL) {
+ item = (fd_lock_item_t *) mem_alloc(sizeof(fd_lock_item_t));
+ if (item == (fd_lock_item_t *) NULL) {
+ errno = ENOMEM;
+ return (NULL);
+ }
+ item->fd = fd;
+ item->refs = 1;
+ item->fd_lock.active = FALSE;
+ item->fd_lock.pending = 0;
+ cond_init(&item->fd_lock.cv, 0, (void *) 0);
+ TAILQ_INSERT_HEAD(list, item, link);
+ } else {
+ item->refs++;
+ }
+ return &item->fd_lock;
+}
+
+/* de-allocate per-fd lock */
+static inline
+void fd_lock_destroy(int fd, fd_lock_t *fd_lock, fd_locks_t *fd_locks) {
+#ifdef MAX_FDLOCKS_PREALLOC
+ if (fd < fd_locks_prealloc)
+ return;
+#endif
+ fd_lock_item_t* item = to_fd_lock_item(fd_lock);
+ item->refs--;
+ if (item->refs <= 0) {
+ TAILQ_REMOVE(to_fd_lock_list(fd_locks), item, link);
+ cond_destroy(&item->fd_lock.cv);
+ mem_free(item, sizeof (*item));
+ }
+}
+
+#endif /* _CLNT_FD_LOCKS_H */