Date: Wed, 4 Jul 2007 17:41:34 +0200 From: "=?iso-8859-1?Q?david.chosrova@libertysurf.fr?=" <david.chosrova@libertysurf.fr> To: "=?iso-8859-1?Q?freebsd-hackers?=" <freebsd-hackers@freebsd.org> Subject: kernel dynamic references Message-ID: <JKNVLA$9473598C09CB973FF45B769C24DFF664@aliceadsl.fr>
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Hi,
I'm new to Freebsd and interested in system programming. So I'have picked up a task from the project ideas list to start with.
(part of) the subject is : "This task is to define and implement a general mechanism for tracking these references and use them in handling module unload requests."
So, to do that, I'have added an "int dynrefs" in struct module (kern_module.c), and functions to increase or decrease this count (module_add/remove_dynrefs(const char * modname) and module_updatedynrefs(const char * modname, int action) ) in kern_module.c.
To avoid unload of a module which has a dynrefs count != 0 , I have modified module_unload(), so that unload is process only if dynrefs=0 or flag=LINKER_UNLOAD_FORCE.
--- module.h.orig Wed Jul 4 10:29:53 2007
+++ module.h Wed Jul 4 10:21:40 2007
@@ -147,7 +147,8 @@
int module_getid(module_t);
module_t module_getfnext(module_t);
void module_setspecific(module_t, modspecific_t *);
-
+int module_add_dynrefs(const char *);
+int module_remove_dynrefs(const char *);
#ifdef MOD_DEBUG
extern int mod_debug;
--- kern_module.c.orig Wed Jul 4 10:33:06 2007
+++ kern_module.c Wed Jul 4 10:21:28 2007
@@ -52,6 +52,7 @@
TAILQ_ENTRY(module) flink; /* all modules in a file */
struct linker_file *file; /* file which contains this module */
int refs; /* reference count */
+ int dynrefs; /* dynamic reference count */
int id; /* unique id number */
char *name; /* module name */
modeventhand_t handler; /* event handler */
@@ -65,6 +66,7 @@
struct sx modules_sx;
static int nextid = 1;
static void module_shutdown(void *, int);
+static int module_updatedynrefs(const char* , int );
static int
modevent_nop(module_t mod, int what, void *arg)
@@ -152,6 +154,7 @@
}
newmod->refs = 1;
newmod->id = nextid++;
+ newmod->dynrefs = 0;
newmod->name = (char *)(newmod + 1);
strcpy(newmod->name, data->name);
newmod->handler = data->evhand ? data->evhand : modevent_nop;
@@ -231,7 +234,9 @@
module_unload(module_t mod, int flags)
{
int error;
- error = MOD_EVENT(mod, MOD_QUIESCE);
+ MOD_SLOCK;
+ (mod->dynrefs == 0) ? (error = MOD_EVENT(mod, MOD_QUIESCE)) : (error = EPERM);
+ MOD_SUNLOCK;
if (error == EOPNOTSUPP || error == EINVAL)
error = 0;
if (flags == LINKER_UNLOAD_NORMAL && error != 0)
@@ -261,6 +266,37 @@
MOD_XLOCK_ASSERT;
mod->data = *datap;
+}
+
+static int
+module_updatedynrefs(const char* modname, int action)
+{
+ module_t mod;
+
+ MOD_XLOCK;
+ mod = module_lookupbyname(modname);
+
+ if(mod == 0) {
+ MOD_XUNLOCK;
+ return(-1);
+ }
+
+ (action == 1) ? mod->dynrefs++ : mod->dynrefs--;
+ MOD_XUNLOCK;
+ return (0);
+}
+
+int
+module_add_dynrefs(const char *modname)
+{
+
+ return (module_updatedynrefs(modname,1));
+}
+
+int
+module_remove_dynrefs(const char * modname)
+{
+ return (module_updatedynrefs(modname,0));
}
/*
I have compiled and tested. with a 6-2 RELEASE. For the test I'have used two dummy module, one adding a dynrefs on the other.
Any comments are welcome.
David chosrova
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