+ modules-de-mutex-more-symbol-lookup-paths-in-the-module-code.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     modules: de-mutex more symbol lookup paths in the module code
has been added to the -mm tree.  Its filename is
     modules-de-mutex-more-symbol-lookup-paths-in-the-module-code.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

The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/

------------------------------------------------------
Subject: modules: de-mutex more symbol lookup paths in the module code
From: Rusty Russell <rusty@rustcorp.com.au>

Kyle McMartin reports sysrq_timer_list_show() can hit the module
mutex; these paths don't need to though, since we long ago changed all
the module list manipulation to occur via stop_machine().

Disabling preemption is enough.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/module.c |   29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

diff -puN kernel/module.c~modules-de-mutex-more-symbol-lookup-paths-in-the-module-code kernel/module.c
--- a/kernel/module.c~modules-de-mutex-more-symbol-lookup-paths-in-the-module-code
+++ a/kernel/module.c
@@ -2218,29 +2218,34 @@ static const char *get_ksymbol(struct mo
 /* For kallsyms to ask for address resolution.  NULL means not found.
    We don't lock, as this is used for oops resolution and races are a
    lesser concern. */
+/* FIXME: Risky: returns a pointer into a module w/o lock */
 const char *module_address_lookup(unsigned long addr,
 				  unsigned long *size,
 				  unsigned long *offset,
 				  char **modname)
 {
 	struct module *mod;
+	const char *ret = NULL;
 
+	preempt_disable();
 	list_for_each_entry(mod, &modules, list) {
 		if (within(addr, mod->module_init, mod->init_size)
 		    || within(addr, mod->module_core, mod->core_size)) {
 			if (modname)
 				*modname = mod->name;
-			return get_ksymbol(mod, addr, size, offset);
+			ret = get_ksymbol(mod, addr, size, offset);
+			break;
 		}
 	}
-	return NULL;
+	preempt_enable();
+	return ret;
 }
 
 int lookup_module_symbol_name(unsigned long addr, char *symname)
 {
 	struct module *mod;
 
-	mutex_lock(&module_mutex);
+	preempt_disable();
 	list_for_each_entry(mod, &modules, list) {
 		if (within(addr, mod->module_init, mod->init_size) ||
 		    within(addr, mod->module_core, mod->core_size)) {
@@ -2250,12 +2255,12 @@ int lookup_module_symbol_name(unsigned l
 			if (!sym)
 				goto out;
 			strlcpy(symname, sym, KSYM_NAME_LEN);
-			mutex_unlock(&module_mutex);
+			preempt_enable();
 			return 0;
 		}
 	}
 out:
-	mutex_unlock(&module_mutex);
+	preempt_enable();
 	return -ERANGE;
 }
 
@@ -2264,7 +2269,7 @@ int lookup_module_symbol_attrs(unsigned 
 {
 	struct module *mod;
 
-	mutex_lock(&module_mutex);
+	preempt_disable();
 	list_for_each_entry(mod, &modules, list) {
 		if (within(addr, mod->module_init, mod->init_size) ||
 		    within(addr, mod->module_core, mod->core_size)) {
@@ -2277,12 +2282,12 @@ int lookup_module_symbol_attrs(unsigned 
 				strlcpy(modname, mod->name, MODULE_NAME_LEN);
 			if (name)
 				strlcpy(name, sym, KSYM_NAME_LEN);
-			mutex_unlock(&module_mutex);
+			preempt_enable();
 			return 0;
 		}
 	}
 out:
-	mutex_unlock(&module_mutex);
+	preempt_enable();
 	return -ERANGE;
 }
 
@@ -2291,7 +2296,7 @@ int module_get_kallsym(unsigned int symn
 {
 	struct module *mod;
 
-	mutex_lock(&module_mutex);
+	preempt_disable();
 	list_for_each_entry(mod, &modules, list) {
 		if (symnum < mod->num_symtab) {
 			*value = mod->symtab[symnum].st_value;
@@ -2300,12 +2305,12 @@ int module_get_kallsym(unsigned int symn
 				KSYM_NAME_LEN);
 			strlcpy(module_name, mod->name, MODULE_NAME_LEN);
 			*exported = is_exported(name, mod);
-			mutex_unlock(&module_mutex);
+			preempt_enable();
 			return 0;
 		}
 		symnum -= mod->num_symtab;
 	}
-	mutex_unlock(&module_mutex);
+	preempt_enable();
 	return -ERANGE;
 }
 
@@ -2328,6 +2333,7 @@ unsigned long module_kallsyms_lookup_nam
 	unsigned long ret = 0;
 
 	/* Don't lock: we're in enough trouble already. */
+	preempt_disable();
 	if ((colon = strchr(name, ':')) != NULL) {
 		*colon = '\0';
 		if ((mod = find_module(name)) != NULL)
@@ -2338,6 +2344,7 @@ unsigned long module_kallsyms_lookup_nam
 			if ((ret = mod_find_symname(mod, name)) != 0)
 				break;
 	}
+	preempt_enable();
 	return ret;
 }
 #endif /* CONFIG_KALLSYMS */
_

Patches currently in -mm which might be from rusty@rustcorp.com.au are

git-kbuild.patch
git-kvm.patch
git-libata-all.patch
git-scsi-misc.patch
kallsyms-should-prefer-non-weak-symbols.patch
virtio_net-remove-double-ether_setup.patch
modules-handle-symbols-that-have-a-zero-value.patch
modules-include-sectionsh-to-avoid-defining-linker-variables.patch
modules-fold-percpu_modcopy-into-modulec-and-get-rid-of-the-macro-from-hell.patch
modules-de-mutex-more-symbol-lookup-paths-in-the-module-code.patch
reiser4.patch