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Commit f93b99e8 authored by Adam Wujek's avatar Adam Wujek Committed by Adam Wujek
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[Feature: #227] userspace/libwr: allow writer to reopen shmem 

Signed-off-by: 's avatarAdam Wujek <dev_public@wujek.eu>
parent 926d79b6
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Showing with 36 additions and 9 deletions
userspace/libwr/include/libwr/shmem.h
View file @ f93b99e8
......@@ -9,6 +9,7 @@
#define WRS_SHM_DEFAULT_PATH "/dev/shm"
#define WRS_SHM_FILE "wrs-shmem-%i"
#define WRS_SHM_MAPADDR 0x10000000
#define WRS_SHM_MIN_SIZE (4*1024)
#define WRS_SHM_MAX_SIZE (512*1024)
......
userspace/libwr/shmem.c
View file @ f93b99e8
......@@ -49,6 +49,7 @@ struct wrs_shm_head *wrs_shm_get(enum wrs_shm_name name_id, char *name,
char fname[64];
int write_access = flags & WRS_SHM_WRITE;
int fd;
void *prev_mapbase;
if (name_id >= WRS_SHM_N_NAMES) {
errno = EINVAL;
......@@ -70,7 +71,8 @@ struct wrs_shm_head *wrs_shm_get(enum wrs_shm_name name_id, char *name,
write(fd, "", 1);
}
map = mmap(0, WRS_SHM_MAX_SIZE,
map = mmap((void *)(WRS_SHM_MAPADDR + WRS_SHM_MAX_SIZE * name_id),
WRS_SHM_MAX_SIZE,
PROT_READ | (write_access ? PROT_WRITE : 0),
MAP_SHARED, fd, 0);
if (map == MAP_FAILED) {
......@@ -110,21 +112,45 @@ struct wrs_shm_head *wrs_shm_get(enum wrs_shm_name name_id, char *name,
close(fd);
return NULL;
}
head->fd = fd;
head->sequence = 1; /* a sort of lock */
/* Set mapbase only for the first call of wrs_shm_get.
* At further calls (probably due to a restart of a writter/writer),
* At further calls (probably due to a restart of a writer),
* this is used by wrs_shm_follow to calculate the offset of a given
* pointer from the beginning of shmem. */
if (!head->mapbase)
head->mapbase = head;
if (!head->mapbase || head->mapbase == head) {
head->mapbase = head;
head->data_off = sizeof(*head);
head->data_size = 0;
} else {
/* try to remap at the previous mapbase */
prev_mapbase = head->mapbase;
munmap(map, WRS_SHM_MAX_SIZE);
/* Do not use MAP_FIXED because it unmaps previous mappings
* that overlap with the current one */
map = mmap(prev_mapbase, WRS_SHM_MAX_SIZE,
PROT_READ | (write_access ? PROT_WRITE : 0),
MAP_SHARED, fd, 0);
if (map == MAP_FAILED) {
close(fd);
return NULL; /* keep errno */
}
if (map != prev_mapbase) {
/* mapped at the different address than expected,
* clean the mapped memory (pointers may be unusable)*/
memset(map, 0, stbuf.st_size);
}
head = map;
/* Keep data_off and data_size as it was to allow further
* memory allocations */
}
head->fd = fd;
strncpy(head->name, name, sizeof(head->name));
head->name[sizeof(head->name) - 1] = '\0';
head->stamp = 0;
head->data_off = sizeof(*head);
head->data_size = 0;
if (flags & wrs_shm_locked)
head->sequence = 1; /* a sort of lock */
else
......
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