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Date: Mon, 25 Aug 2014 10:55:48 +0000
From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To: Rusty Russell <rusty@...tcorp.com.au>
Cc: Lucas De Marchi <lucas.demarchi@...el.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Josh Poimboeuf <jpoimboe@...hat.com>
Subject: [RFC PATCH 4/5] module: Lock up a module when loading with a LOCLUP
flag
Lock-up a module in kernel so that it is not removed unless
forcibly unload. This is done by loading a module with
MODULE_INIT_LOCKUP_MODULE flag (via finit_module).
This speeds up try_module_get by skipping refcount inc/dec for
the locked modules.
Note that this flag requires to update libkmod to support it.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
---
include/linux/module.h | 6 ++++++
include/uapi/linux/module.h | 1 +
kernel/module.c | 28 ++++++++++++++++++++--------
3 files changed, 27 insertions(+), 8 deletions(-)
diff --git a/include/linux/module.h b/include/linux/module.h
index 71f282a..670cb2e 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -205,6 +205,7 @@ struct module_use {
enum module_state {
MODULE_STATE_LIVE, /* Normal state. */
+ MODULE_STATE_LOCKUP, /* Module is never removed except forced */
MODULE_STATE_COMING, /* Full formed, running module_init. */
MODULE_STATE_GOING, /* Going away. */
MODULE_STATE_UNFORMED, /* Still setting it up. */
@@ -390,6 +391,11 @@ static inline int module_is_live(struct module *mod)
return mod->state != MODULE_STATE_GOING;
}
+static inline int module_is_locked(struct module *mod)
+{
+ return mod->state == MODULE_STATE_LOCKUP;
+}
+
struct module *__module_text_address(unsigned long addr);
struct module *__module_address(unsigned long addr);
bool is_module_address(unsigned long addr);
diff --git a/include/uapi/linux/module.h b/include/uapi/linux/module.h
index 38da425..8195603 100644
--- a/include/uapi/linux/module.h
+++ b/include/uapi/linux/module.h
@@ -4,5 +4,6 @@
/* Flags for sys_finit_module: */
#define MODULE_INIT_IGNORE_MODVERSIONS 1
#define MODULE_INIT_IGNORE_VERMAGIC 2
+#define MODULE_INIT_LOCKUP_MODULE 4
#endif /* _UAPI_LINUX_MODULE_H */
diff --git a/kernel/module.c b/kernel/module.c
index 3bd0dc9..85ffc1d 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -753,7 +753,7 @@ static int __try_stop_module(void *_sref)
struct stopref *sref = _sref;
/* If it's not unused, quit unless we're forcing. */
- if (module_refcount(sref->mod) != 0) {
+ if (module_is_locked(sref->mod) || module_refcount(sref->mod) != 0) {
if (!(*sref->forced = try_force_unload(sref->flags)))
return -EWOULDBLOCK;
}
@@ -830,7 +830,8 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user,
}
/* Doing init or already dying? */
- if (mod->state != MODULE_STATE_LIVE) {
+ if (mod->state != MODULE_STATE_LIVE &&
+ mod->state != MODULE_STATE_LOCKUP) {
/* FIXME: if (force), slam module count damn the torpedoes */
pr_debug("%s already dying\n", mod->name);
ret = -EBUSY;
@@ -947,6 +948,9 @@ bool try_module_get(struct module *module)
bool ret = true;
if (module) {
+ if (module_is_locked(module))
+ goto end;
+
preempt_disable();
if (likely(module_is_live(module))) {
@@ -957,13 +961,14 @@ bool try_module_get(struct module *module)
preempt_enable();
}
+end:
return ret;
}
EXPORT_SYMBOL(try_module_get);
void module_put(struct module *module)
{
- if (module) {
+ if (module && !module_is_locked(module)) {
preempt_disable();
smp_wmb(); /* see comment in module_refcount */
__this_cpu_inc(module->refptr->decs);
@@ -1026,6 +1031,7 @@ static ssize_t show_initstate(struct module_attribute *mattr,
switch (mk->mod->state) {
case MODULE_STATE_LIVE:
+ case MODULE_STATE_LOCKUP:
state = "live";
break;
case MODULE_STATE_COMING:
@@ -2981,6 +2987,7 @@ static bool finished_loading(const char *name)
mutex_lock(&module_mutex);
mod = find_module_all(name, strlen(name), true);
ret = !mod || mod->state == MODULE_STATE_LIVE
+ || mod->state == MODULE_STATE_LOCKUP
|| mod->state == MODULE_STATE_GOING;
mutex_unlock(&module_mutex);
@@ -2999,7 +3006,7 @@ static void do_mod_ctors(struct module *mod)
}
/* This is where the real work happens */
-static int do_init_module(struct module *mod)
+static int do_init_module(struct module *mod, bool locked)
{
int ret = 0;
@@ -3034,7 +3041,7 @@ static int do_init_module(struct module *mod)
}
/* Now it's a first class citizen! */
- mod->state = MODULE_STATE_LIVE;
+ mod->state = locked ? MODULE_STATE_LOCKUP : MODULE_STATE_LIVE;
blocking_notifier_call_chain(&module_notify_list,
MODULE_STATE_LIVE, mod);
@@ -3290,7 +3297,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
/* Done! */
trace_module_load(mod);
- return do_init_module(mod);
+ return do_init_module(mod, flags & MODULE_INIT_LOCKUP_MODULE);
bug_cleanup:
/* module_bug_cleanup needs module_mutex protection */
@@ -3358,8 +3365,9 @@ SYSCALL_DEFINE3(finit_module, int, fd, const char __user *, uargs, int, flags)
pr_debug("finit_module: fd=%d, uargs=%p, flags=%i\n", fd, uargs, flags);
- if (flags & ~(MODULE_INIT_IGNORE_MODVERSIONS
- |MODULE_INIT_IGNORE_VERMAGIC))
+ if (flags & ~(MODULE_INIT_IGNORE_MODVERSIONS |
+ MODULE_INIT_IGNORE_VERMAGIC |
+ MODULE_INIT_LOCKUP_MODULE))
return -EINVAL;
err = copy_module_from_fd(fd, &info);
@@ -3602,10 +3610,14 @@ static char *module_flags(struct module *mod, char *buf)
BUG_ON(mod->state == MODULE_STATE_UNFORMED);
if (mod->taints ||
+ mod->state == MODULE_STATE_LOCKUP ||
mod->state == MODULE_STATE_GOING ||
mod->state == MODULE_STATE_COMING) {
buf[bx++] = '(';
bx += module_flags_taint(mod, buf + bx);
+ /* Show a - for module-is-locked */
+ if (mod->state == MODULE_STATE_LOCKUP)
+ buf[bx++] = '*';
/* Show a - for module-is-being-unloaded */
if (mod->state == MODULE_STATE_GOING)
buf[bx++] = '-';
--
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