* that I may as well take advantage of sysV shared memory too.
* Actually, semaphores seem to be buggy, or I was using them
* incorrectly :-). I've replaced the sysV semaphore with a shared
- * integer controlled with Interlocked functions.
-
+ * integer controlled with Interlocked functions. And I've since
+ * replaced that with a separate process to serialise access to the
+ * shared memory, to avoid the possibility of DOS by leaving the
+ * shared memory locked, and also to allow the shared memory to be
+ * cleaned up.
+ *
* mmap() files have the advantage of avoiding namespace collisions,
* but have the disadvantage of needing cleaning up, and also msync().
* sysV shared memory has a really stupid way of getting random key
* IDs, which can lead to collisions.
*
- * I deliberately don't ever delete the shared memory: I'd like to
- * have been able to set the shared memory segment to destroy itself
- * on last close, but it doesn't support that. (Setting IPC_RMID on a
- * segment causes subsequent shmat() with the same key to get a new
- * segment :-( ). The function to delete the shared memory segment is
- * only called from a debugging tool (mono/handles/shmdel).
+ * Having tried sysv shm, I tested mmap() and found that MAP_SHARED
+ * makes msync() irrelevent, and both types need cleaning up. Seeing
+ * as mmap() doesn't suffer from the bonkers method of allocating
+ * segments, it seems to be the best method.
*
- * w32 processes do not have the POSIX parent-child relationship, so a
- * process handle is available to any other process to find out exit
- * status. Handles are destroyed when the last reference to them is
- * closed. New handles can be created for long lasting items such as
- * processes or threads, and also for named synchronisation objects so
- * long as these haven't been deleted by having the last referencing
- * handle closed.
+ * This shared memory is needed because w32 processes do not have the
+ * POSIX parent-child relationship, so a process handle is available
+ * to any other process to find out exit status. Handles are
+ * destroyed when the last reference to them is closed. New handles
+ * can be created for long lasting items such as processes or threads,
+ * and also for named synchronisation objects so long as these haven't
+ * been deleted by having the last referencing handle closed.
*/
+
#include <config.h>
#include <glib.h>
#include <stdio.h>
+#include <fcntl.h>
#include <unistd.h>
+#include <sys/mman.h>
#include <sys/types.h>
-#include <sys/ipc.h>
-#include <sys/shm.h>
+#include <sys/stat.h>
#include <errno.h>
#include <string.h>
-#include <fcntl.h>
#include <mono/io-layer/wapi.h>
#include <mono/io-layer/wapi-private.h>
#undef DEBUG
+static guchar *shared_file (void)
+{
+ static guchar *file=NULL;
+ guchar *name, *dir;
+
+ if(file!=NULL) {
+ return(file);
+ }
+
+ /* Change the filename whenever the format of the contents
+ * changes
+ */
+ name=g_strdup_printf ("shared_data-%d", _WAPI_HANDLE_VERSION);
+
+ /* I don't know how nfs affects mmap. If mmap() of files on
+ * nfs mounts breaks, then there should be an option to set
+ * the directory.
+ */
+ file=g_build_filename (g_get_home_dir (), ".wapi", name, NULL);
+ g_free (name);
+
+ /* No need to check if the dir already exists or check
+ * mkdir() errors, because on any error the open() call will
+ * report the problem.
+ */
+ dir=g_path_get_dirname (file);
+ mkdir (dir, 0755);
+ g_free (dir);
+
+ return(file);
+}
+
/*
* _wapi_shm_attach:
- * @daemon: Is it the daemon trying to attach to the segment
* @success: Was it a success
- * @shm_id: The ID of the segment created/attached to
*
- * Attach to the shared memory segment or create it if it did not
+ * Attach to the shared memory file or create it if it did not
* exist. If it was created and daemon was FALSE a new daemon is
- * forked into existence. Returns the memory area the segment was
- * attached to.
+ * forked into existence. Returns the memory area the file was mmapped
+ * to.
*/
-gpointer _wapi_shm_attach (gboolean daemon, gboolean *success, int *shm_id)
+gpointer _wapi_shm_attach (gboolean *success)
{
gpointer shm_seg;
- key_t key;
+ int fd;
gboolean fork_daemon=FALSE;
+ struct stat statbuf;
struct _WapiHandleShared_list *data;
int tries;
-
- /*
- * This is an attempt to get a unique key id. The first arg
- * to ftok is a path, so when the config file support is done
- * we should use that.
- */
- key=ftok (g_get_home_dir (), _WAPI_HANDLE_VERSION);
+ int wanted_size=sizeof(struct _WapiHandleShared_list) +
+ _WAPI_SHM_SCRATCH_SIZE;
try_again:
- *shm_id=shmget (key, sizeof(struct _WapiHandleShared_list)+
- _WAPI_SHM_SCRATCH_SIZE, IPC_CREAT | IPC_EXCL | 0600);
- if(*shm_id==-1 && errno==EEXIST) {
- /* Cool, we dont have to fork the handle daemon, but
- * we still need to try and get the shm_id.
- */
- *shm_id=shmget (key, 0, 0600);
-
- /* it's possible that the shared memory segment was
- * deleted in between seeing if it exists, and
- * attaching it. If we got an error here, just try
- * attaching it again.
+ /* No O_CREAT yet, because we need to initialise the file if
+ * we have to create it.
+ */
+ fd=open (shared_file (), O_RDWR, 0600);
+ if(fd==-1 && errno==ENOENT) {
+ /* OK, its up to us to create it. O_EXCL to avoid a
+ * race condition where two processes can
+ * simultaneously try and create the file
*/
- if(*shm_id==-1) {
+ fd=open (shared_file (), O_CREAT|O_EXCL|O_RDWR, 0600);
+ if(fd==-1 && errno==EEXIST) {
+ /* It's possible that the file was created in
+ * between finding it didn't exist, and trying
+ * to create it. Just try opening it again
+ */
goto try_again;
- }
- } else if (*shm_id!=-1) {
- /* We created the shared memory segment, so we need to
- * fork the handle daemon too
- */
- fork_daemon=TRUE;
+ } else if (fd==-1) {
+ g_critical (G_GNUC_PRETTY_FUNCTION
+ ": shared file [%s] open error: %s",
+ shared_file (), g_strerror (errno));
+ exit (-1);
+ } else {
+ /* We created the file, so we need to expand
+ * the file and fork the handle daemon too
+ */
+ if(lseek (fd, wanted_size, SEEK_SET)==-1) {
+ g_critical (G_GNUC_PRETTY_FUNCTION ": shared file [%s] lseek error: %s", shared_file (), g_strerror (errno));
+ _wapi_shm_destroy ();
+ exit (-1);
+ }
+
+ if(write (fd, "", 1)==-1) {
+ g_critical (G_GNUC_PRETTY_FUNCTION ": shared file [%s] write error: %s", shared_file (), g_strerror (errno));
+ _wapi_shm_destroy ();
+ exit (-1);
+ }
+
+ fork_daemon=TRUE;
- /* sysv shared mem is set to all zero when allocated,
- * so we don't need to do any more initialisation here
- */
- } else {
- /* Some error other than EEXIST */
- g_critical (G_GNUC_PRETTY_FUNCTION ": shmget error: %s",
- strerror (errno));
+ /* The contents of the file is set to all
+ * zero, because it is opened up with lseek,
+ * so we don't need to do any more
+ * initialisation here
+ */
+ }
+ } else if(fd==-1) {
+ g_critical (G_GNUC_PRETTY_FUNCTION
+ ": shared file [%s] open error: %s",
+ shared_file (), g_strerror (errno));
exit (-1);
+ } else {
+ /* We dont need to fork the handle daemon */
}
- /* From now on, we need to delete the shm segment before
- * exiting on error if we created it (ie, if
- * fork_daemon==TRUE)
+ /* From now on, we need to delete the file before exiting on
+ * error if we created it (ie, if fork_daemon==TRUE)
+ */
+
+ /* Use stat to find the file size (instead of hard coding it)
+ * so that we can expand the file later if needed (for more
+ * handles or scratch space, though that will require a tweak
+ * to the file format to store the count).
*/
- shm_seg=shmat (*shm_id, NULL, 0);
- if(shm_seg==(gpointer)-1) {
- g_critical (G_GNUC_PRETTY_FUNCTION ": shmat error: %s",
- strerror (errno));
+ if(fstat (fd, &statbuf)==-1) {
+ g_critical (G_GNUC_PRETTY_FUNCTION ": fstat error: %s",
+ g_strerror (errno));
if(fork_daemon==TRUE) {
_wapi_shm_destroy ();
}
exit (-1);
}
- if(daemon==TRUE) {
- /* No more to do in the daemon */
- *success=TRUE;
- return(shm_seg);
+ if(statbuf.st_size < wanted_size) {
+#ifdef HAVE_LARGE_FILE_SUPPORT
+ /* Keep gcc quiet... */
+ g_critical (G_GNUC_PRETTY_FUNCTION ": shared file [%s] is not big enough! (found %lld, need %d bytes)", shared_file (), statbuf.st_size, wanted_size);
+#else
+ g_critical (G_GNUC_PRETTY_FUNCTION ": shared file [%s] is not big enough! (found %ld, need %d bytes)", shared_file (), statbuf.st_size, wanted_size);
+#endif
+ if(fork_daemon==TRUE) {
+ _wapi_shm_destroy ();
+ }
+ exit (-1);
+ }
+
+ shm_seg=mmap (NULL, statbuf.st_size, PROT_READ|PROT_WRITE, MAP_SHARED,
+ fd, 0);
+ if(shm_seg==MAP_FAILED) {
+ g_critical (G_GNUC_PRETTY_FUNCTION ": mmap error: %s",
+ g_strerror (errno));
+ if(fork_daemon==TRUE) {
+ _wapi_shm_destroy ();
+ }
+ exit (-1);
}
+ close (fd);
data=shm_seg;
}
/* _wapi_daemon_main() does not return */
- _wapi_daemon_main ();
+ _wapi_daemon_main (data);
/* But just in case... */
data->daemon_running=DAEMON_DIED_AT_STARTUP;
void _wapi_shm_destroy (void)
{
#ifndef DISABLE_SHARED_HANDLES
- int shm_id;
- key_t key;
-
- /*
- * This is an attempt to get a unique key id. The
- * first arg to ftok is a path, so when the config
- * file support is done we should use that.
- */
- key=ftok (g_get_home_dir (), _WAPI_HANDLE_VERSION);
-
- shm_id=shmget (key, 0, 0600);
- if(shm_id==-1 && errno==ENOENT) {
- return;
- } else if (shm_id==-1) {
- g_message (G_GNUC_PRETTY_FUNCTION ": shmget error: %s",
- strerror (errno));
- exit (-1);
- }
- if(shmctl (shm_id, IPC_RMID, NULL)==-1) {
- g_message (G_GNUC_PRETTY_FUNCTION ": shmctl error: %s",
- strerror (errno));
- exit (-1);
- }
+#ifdef DEBUG
+ g_message (G_GNUC_PRETTY_FUNCTION ": unlinking %s", shared_file ());
+#endif
+ unlink (shared_file ());
#endif /* DISABLE_SHARED_HANDLES */
}
+
projects / mono.git / commitdiff