The patch titled
modules: remove modlist_lock
has been added to the -mm tree. Its filename is
modules-remove-modlist_lock.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: modules: remove modlist_lock
From: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Now we always use stop_machine for module insertion or deletion, we no
longer need the modlist_lock: merely disabling preemption is sufficient to
block against list manipulation. This avoids deadlock on OOPSen where we
can potentially grab the lock twice.
Bug: 8695
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Tobias Oed <tobiasoed@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/module.c | 36 +++++++++++++++---------------------
1 files changed, 15 insertions(+), 21 deletions(-)
diff -puN kernel/module.c~modules-remove-modlist_lock kernel/module.c
--- a/kernel/module.c~modules-remove-modlist_lock
+++ a/kernel/module.c
@@ -61,10 +61,8 @@ extern int module_sysfs_initialized;
/* If this is set, the section belongs in the init part of the module */
#define INIT_OFFSET_MASK (1UL << (BITS_PER_LONG-1))
-/* Protects module list */
-static DEFINE_SPINLOCK(modlist_lock);
-
-/* List of modules, protected by module_mutex AND modlist_lock */
+/* List of modules, protected by module_mutex or preempt_disable
+ * (add/delete uses stop_machine). */
static DEFINE_MUTEX(module_mutex);
static LIST_HEAD(modules);
static DECLARE_MUTEX(notify_mutex);
@@ -772,14 +770,13 @@ static void print_unload_info(struct seq
void __symbol_put(const char *symbol)
{
struct module *owner;
- unsigned long flags;
const unsigned long *crc;
- spin_lock_irqsave(&modlist_lock, flags);
+ preempt_disable();
if (!__find_symbol(symbol, &owner, &crc, 1))
BUG();
module_put(owner);
- spin_unlock_irqrestore(&modlist_lock, flags);
+ preempt_enable();
}
EXPORT_SYMBOL(__symbol_put);
@@ -1248,14 +1245,14 @@ static void free_module(struct module *m
void *__symbol_get(const char *symbol)
{
struct module *owner;
- unsigned long value, flags;
+ unsigned long value;
const unsigned long *crc;
- spin_lock_irqsave(&modlist_lock, flags);
+ preempt_disable();
value = __find_symbol(symbol, &owner, &crc, 1);
if (value && !strong_try_module_get(owner))
value = 0;
- spin_unlock_irqrestore(&modlist_lock, flags);
+ preempt_enable();
return (void *)value;
}
@@ -2368,11 +2365,10 @@ const struct seq_operations modules_op =
/* Given an address, look for it in the module exception tables. */
const struct exception_table_entry *search_module_extables(unsigned long addr)
{
- unsigned long flags;
const struct exception_table_entry *e = NULL;
struct module *mod;
- spin_lock_irqsave(&modlist_lock, flags);
+ preempt_disable();
list_for_each_entry(mod, &modules, list) {
if (mod->num_exentries == 0)
continue;
@@ -2383,7 +2379,7 @@ const struct exception_table_entry *sear
if (e)
break;
}
- spin_unlock_irqrestore(&modlist_lock, flags);
+ preempt_enable();
/* Now, if we found one, we are running inside it now, hence
we cannot unload the module, hence no refcnt needed. */
@@ -2395,25 +2391,24 @@ const struct exception_table_entry *sear
*/
int is_module_address(unsigned long addr)
{
- unsigned long flags;
struct module *mod;
- spin_lock_irqsave(&modlist_lock, flags);
+ preempt_disable();
list_for_each_entry(mod, &modules, list) {
if (within(addr, mod->module_core, mod->core_size)) {
- spin_unlock_irqrestore(&modlist_lock, flags);
+ preempt_enable();
return 1;
}
}
- spin_unlock_irqrestore(&modlist_lock, flags);
+ preempt_enable();
return 0;
}
-/* Is this a valid kernel address? We don't grab the lock: we are oopsing. */
+/* Is this a valid kernel address? */
struct module *__module_text_address(unsigned long addr)
{
struct module *mod;
@@ -2428,11 +2423,10 @@ struct module *__module_text_address(uns
struct module *module_text_address(unsigned long addr)
{
struct module *mod;
- unsigned long flags;
- spin_lock_irqsave(&modlist_lock, flags);
+ preempt_disable();
mod = __module_text_address(addr);
- spin_unlock_irqrestore(&modlist_lock, flags);
+ preempt_enable();
return mod;
}
_
Patches currently in -mm which might be from rusty@xxxxxxxxxxxxxxx are
git-kbuild.patch
paravirt-helper-to-disable-all-io-space-fix.patch
mm-clean-up-and-kernelify-shrinker-registration.patch
mm-clean-up-and-kernelify-shrinker-registration-vs-git-nfs.patch
use-menuconfig-objects-ii-module-menu.patch
fix-stop_machine_run-problem-with-naughty-real-time-process.patch
cpu-hotplug-fix-ksoftirqd-termination-on-cpu-hotplug-with-naughty-realtime-process.patch
cpu-hotplug-fix-ksoftirqd-termination-on-cpu-hotplug-with-naughty-realtime-process-fix.patch
modules-remove-modlist_lock.patch
lguest-export-symbols-for-lguest-as-a-module.patch
lguest-the-guest-code.patch
fix-lguest-w-lockdep.patch
lguest-the-guest-code-lguest-fix-tsc-divide-error-0000-boot-crash.patch
lguest-the-host-code.patch
lguest-the-host-code-lguest-vs-clockevents-fix-resume-logic.patch
lguest-the-asm-offsets.patch
lguest-the-makefile-and-kconfig.patch
lguest-the-console-driver.patch
lguest-the-net-driver.patch
lguest-the-block-driver.patch
lguest-the-documentation-example-launcher.patch
readahead-introduce-pg_readahead.patch
readahead-add-look-ahead-support-to-__do_page_cache_readahead.patch
readahead-min_ra_pages-max_ra_pages-macros.patch
readahead-data-structure-and-routines.patch
readahead-on-demand-readahead-logic.patch
readahead-convert-filemap-invocations.patch
readahead-convert-splice-invocations.patch
readahead-convert-ext3-ext4-invocations.patch
readahead-remove-the-old-algorithm.patch
readahead-move-synchronous-readahead-call-out-of-splice-loop.patch
readahead-pass-real-splice-size.patch
mm-share-pg_readahead-and-pg_reclaim.patch
readahead-split-ondemand-readahead-interface-into-two-functions.patch
readahead-sanify-file_ra_state-names.patch
define-new-percpu-interface-for-shared-data-version-4.patch
use-the-new-percpu-interface-for-shared-data-version-4.patch
mm-clean-up-and-kernelify-shrinker-registration-reiser4.patch
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