X-Git-Url: http://git.lttng.org./?a=blobdiff_plain;f=libringbuffer%2Fshm.c;h=1ac59f9eee138c2744a5ada5bd58c05476de9800;hb=71be0c5340258bbb9fe728451790dd113be2f1ec;hp=461befb99db5ed45cde5dcdcfecb860df06003b3;hpb=6daf0c26e948e0f2270c283a6b311fba9591843d;p=lttng-ust.git

diff --git a/libringbuffer/shm.c b/libringbuffer/shm.c
index 461befb9..1ac59f9e 100644
--- a/libringbuffer/shm.c
+++ b/libringbuffer/shm.c
@@ -19,7 +19,6 @@
  */
 
 #define _LGPL_SOURCE
-#include <config.h>
 #include "shm.h"
 #include <unistd.h>
 #include <fcntl.h>
@@ -129,25 +128,35 @@ 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;
 	}
@@ -519,6 +528,6 @@ 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;
 }