MFC kern_linker.c 1.133 and related changes:

- push Giant into linker_reference_module();
- introduce linker_release_module(), which also takes care of
  proper locking.

The latter also fixes a missing mtx_loc/unlock in subr_firmware.c .

Apparently, digi.c is the only external client of linker_reference_module()
which is a bit suspicious - perhaps dev/digi/ could make with a bit
of review from someone knowledgeable to check how the function is used,
and whether it could be replaced by something else.

sys/dev/digi/digi.c

@@ -795,7 +795,7 @@ digi_loadmoduledata(struct digi_softc *sc)
 	free(sym, M_TEMP);
 	if (symptr == NULL) {
 		printf("digi_%s.ko: Symbol `%s' not found\n", sc->module, sym);
-		linker_file_unload(lf, LINKER_UNLOAD_FORCE);
+		linker_release_module(NULL, NULL, lf);
 		return (EINVAL);
 	}
 
@@ -803,7 +803,7 @@ digi_loadmoduledata(struct digi_softc *sc)
 	if (digi_mod->dm_version != DIGI_MOD_VERSION) {
 		printf("digi_%s.ko: Invalid version %d (need %d)\n",
 		    sc->module, digi_mod->dm_version, DIGI_MOD_VERSION);
-		linker_file_unload(lf, LINKER_UNLOAD_FORCE);
+		linker_release_module(NULL, NULL, lf);
 		return (EINVAL);
 	}
 
@@ -825,7 +825,7 @@ digi_loadmoduledata(struct digi_softc *sc)
 		bcopy(digi_mod->dm_link.data, sc->link.data, sc->link.size);
 	}
 
-	linker_file_unload(lf, LINKER_UNLOAD_FORCE);
+	linker_release_module(NULL, NULL, lf);
 
 	return (0);
 }

sys/kern/kern_linker.c

@@ -397,14 +397,44 @@ linker_reference_module(const char *modname, struct mod_depend *verinfo,
     linker_file_t *result)
 {
 	modlist_t mod;
+	int error;
 
+	mtx_lock(&Giant);
 	if ((mod = modlist_lookup2(modname, verinfo)) != NULL) {
 		*result = mod->container;
 		(*result)->refs++;
+		mtx_unlock(&Giant);
 		return (0);
 	}
 
-	return (linker_load_module(NULL, modname, NULL, verinfo, result));
+	error = linker_load_module(NULL, modname, NULL, verinfo, result);
+	mtx_unlock(&Giant);
+	return (error);
+}
+
+int
+linker_release_module(const char *modname, struct mod_depend *verinfo,
+    linker_file_t lf)
+{
+	modlist_t mod;
+	int error;
+
+	mtx_lock(&Giant);
+	if (lf == NULL) {
+		KASSERT(modname != NULL,
+		    ("linker_release_module: no file or name"));
+		mod = modlist_lookup2(modname, verinfo);
+		if (mod == NULL) {
+			mtx_unlock(&Giant);
+			return (ESRCH);
+		}
+		lf = mod->container;
+	} else
+		KASSERT(modname == NULL && verinfo == NULL,
+		    ("linker_release_module: both file and name"));
+	error =	linker_file_unload(lf, LINKER_UNLOAD_NORMAL);
+	mtx_unlock(&Giant);
+	return (error);
 }
 
 linker_file_t

sys/kern/subr_firmware.c

@@ -197,9 +197,7 @@ firmware_get(const char *imagename)
 		    "load firmware image %s\n", __func__, imagename);
 		return NULL;
 	}
-	mtx_lock(&Giant);		/* XXX */
 	(void) linker_reference_module(imagename, NULL, &result);
-	mtx_unlock(&Giant);		/* XXX */
 	requested_load = 1;
 	goto again;		/* sort of an Algol-style for loop */
 }
@@ -218,7 +216,7 @@ unloadentry(void *unused1, int unused2)
 		 */
 		mtx_unlock(&firmware_mtx);
 
-		linker_file_unload(fp->file, LINKER_UNLOAD_NORMAL);
+		linker_release_module(NULL, NULL, fp->file);
 
 		mtx_lock(&firmware_mtx);
 		clearentry(fp, 0);

sys/sys/linker.h

@@ -117,6 +117,14 @@ int linker_load_module(const char *_kldname, const char *_modname,
 int linker_reference_module(const char* _modname, struct mod_depend *_verinfo,
 			    linker_file_t* _result);
 
+/*
+ * Release a reference to a module, unloading it if there are no more
+ * references.  Note that one should either provide a module name and
+ * optional version info or a linker file, but not both.
+ */
+int linker_release_module(const char *_modname, struct mod_depend *_verinfo,
+			    linker_file_t _file);
+
 /*
  * Find a currently loaded file given its filename.
  */