Lionel Perrin wrote:
> Hi,
>
> I got some problems with shared memory.
> I started from the shm_open example from opengroup.org.
> When I compile it as non real time tasks, it works properly. But since I
> tried to compile it with
> gcc $(xeno-config --posix-cflags) shm_open.c $(xeno-config
> --posix-ldflags) -o xeno_shm_open,
> i get an EINVAL error from ftruncate that i can fix.
>
> Does shm under xenomai require particular things ?
When applying the attached patch to xenomai (do not forget to rebuild
the kernel), the attached program compiled with the attached Makefile
works here.
--
Gilles Chanteperdrix.
Index: ksrc/skins/posix/shm.c
===================================================================
--- ksrc/skins/posix/shm.c (revision 1143)
+++ ksrc/skins/posix/shm.c (working copy)
@@ -516,10 +516,8 @@
is aligned). */
if (len)
{
- len += PAGE_SIZE + xnheap_overhead(len, PAGE_SIZE);
+ len += PAGE_SIZE + PAGE_ALIGN(xnheap_overhead(len, PAGE_SIZE));
len = PAGE_ALIGN(len);
- if (len == 2 * PAGE_SIZE)
- len = 3 * PAGE_SIZE;
}
err = 0;
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
#define MAX_LEN 10000
struct region { /* Defines "structure" of shared memory */
int len;
char buf[MAX_LEN];
};
struct region *rptr;
int fd;
int main(int argc, const char *argv[])
{
int fd, status;
mlockall(MCL_CURRENT|MCL_FUTURE);
/* Create shared memory object and set its size */
fd = shm_open("/myregion", O_CREAT | O_RDWR, S_IRUSR | S_IWUSR);
if (fd == -1) {
perror("shm_open");
exit(EXIT_FAILURE);
}
if ((status = ftruncate(fd, sizeof(struct region))) == -1) {
/* Handle error */;
perror("ftruncate");
close(fd);
status = EXIT_FAILURE;
goto close_and_unlink;
}
/* Map shared memory object */
rptr = (struct region *) mmap(NULL,
sizeof(struct region),
PROT_READ | PROT_WRITE,
MAP_SHARED,
fd,
0);
if (rptr == MAP_FAILED) {
/* Handle error */;
perror("mmap");
status = EXIT_FAILURE;
goto close_and_unlink;
}
/* Now we can refer to mapped region using fields of rptr;
for example, rptr->len */
munmap(rptr, sizeof(struct region));
close_and_unlink:
close(fd);
shm_unlink("/myregion");
return status;
}
DESTDIR=/home/gilles/files/perso/dev/build/nestor/inst
XENO_CONFIG=$(DESTDIR)/usr/xenomai/bin/xeno-config
CFLAGS:=$(shell DESTDIR=$(DESTDIR) $(XENO_CONFIG) --posix-cflags) -g -O2 -Wall
-W -Werror-implicit-function-declaration
LDFLAGS:=$(shell DESTDIR=$(DESTDIR) $(XENO_CONFIG) --posix-ldflags)
LOADLIBES=-lpthread_rt
all: test_shm
test_shm: test_shm.o
clean:
$(RM) foo foo.o test_shm.o test_shm
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