X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=libringbuffer%2Fshm.c;h=3dbb9f4928a6d81b43c01fc1dbd4dbd3620ebf0c;hb=c0c0989ab70574e09b2f7e8b48c2da6af664a849;hp=44a830af20446142f8e21177b5187e8dfd6d4af0;hpb=fb31eb73d8a4a6d9784ed5c335b7fa3b9684108c;p=lttng-ust.git

diff --git a/libringbuffer/shm.c b/libringbuffer/shm.c
index 44a830af..3dbb9f49 100644
--- a/libringbuffer/shm.c
+++ b/libringbuffer/shm.c
@@ -1,25 +1,10 @@
 /*
- * libringbuffer/shm.c
+ * SPDX-License-Identifier: LGPL-2.1-only
  *
  * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation; only
- * version 2.1 of the License.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #define _LGPL_SOURCE
-#include <config.h>
 #include "shm.h"
 #include <unistd.h>
 #include <fcntl.h>
@@ -129,25 +114,35 @@ struct shm_object *_shm_object_table_alloc_shm(struct shm_object_table *table,
 	}
 	memcpy(obj->wait_fd, waitfd, sizeof(waitfd));
 
-	/* create shm */
+	/*
+	 * Set POSIX shared memory object size
+	 *
+	 * First, use ftruncate() to set its size, some implementations won't
+	 * allow writes past the size set by ftruncate.
+	 * Then, use write() to fill it with zeros, this allows us to fully
+	 * allocate it and detect a shortage of shm space without dealing with
+	 * a SIGBUS.
+	 */
 
 	shmfd = stream_fd;
-	ret = zero_file(shmfd, memory_map_size);
-	if (ret) {
-		PERROR("zero_file");
-		goto error_zero_file;
-	}
 	ret = ftruncate(shmfd, memory_map_size);
 	if (ret) {
 		PERROR("ftruncate");
 		goto error_ftruncate;
 	}
+	ret = zero_file(shmfd, memory_map_size);
+	if (ret) {
+		PERROR("zero_file");
+		goto error_zero_file;
+	}
+
 	/*
 	 * Also ensure the file metadata is synced with the storage by using
-	 * fsync(2).
+	 * fsync(2). Some platforms don't allow fsync on POSIX shm fds, ignore
+	 * EINVAL accordingly.
 	 */
 	ret = fsync(shmfd);
-	if (ret) {
+	if (ret && errno != EINVAL) {
 		PERROR("fsync");
 		goto error_fsync;
 	}
@@ -329,11 +324,6 @@ struct shm_object *shm_object_table_append_shm(struct shm_object_table *table,
 	obj->shm_fd = shm_fd;
 	obj->shm_fd_ownership = 1;
 
-	ret = fcntl(obj->wait_fd[1], F_SETFD, FD_CLOEXEC);
-	if (ret < 0) {
-		PERROR("fcntl");
-		goto error_fcntl;
-	}
 	/* The write end of the pipe needs to be non-blocking */
 	ret = fcntl(obj->wait_fd[1], F_SETFL, O_NONBLOCK);
 	if (ret < 0) {
@@ -524,6 +514,6 @@ struct shm_ref zalloc_shm(struct shm_object *obj, size_t len)
 
 void align_shm(struct shm_object *obj, size_t align)
 {
-	size_t offset_len = offset_align(obj->allocated_len, align);
+	size_t offset_len = lttng_ust_offset_align(obj->allocated_len, align);
 	obj->allocated_len += offset_len;
 }