From 5e458cc0f4770eea45d3c07110f01b3a94c72aa5 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Wed, 22 Oct 2008 10:00:13 -0500
Subject: [PATCH 01/11] module: simplify load_module.

Linus' recent catch of stack overflow in load_module lead me to look
at the code.  A couple of helpers to get a section address and get
objects from a section can help clean things up a little.

(And in case you're wondering, the stack size also dropped from 328 to
284 bytes).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 include/linux/module.h |   2 +-
 kernel/module.c        | 235 +++++++++++++++++------------------------
 2 files changed, 100 insertions(+), 137 deletions(-)

diff --git a/include/linux/module.h b/include/linux/module.h
index 5d2970cdce93..eddf27db442b 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -277,7 +277,7 @@ struct module
 
 	/* Exception table */
 	unsigned int num_exentries;
-	const struct exception_table_entry *extable;
+	struct exception_table_entry *extable;
 
 	/* Startup function. */
 	int (*init)(void);
diff --git a/kernel/module.c b/kernel/module.c
index 0d8d21ee792c..3d256681ab64 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -132,6 +132,29 @@ static unsigned int find_sec(Elf_Ehdr *hdr,
 	return 0;
 }
 
+/* Find a module section, or NULL. */
+static void *section_addr(Elf_Ehdr *hdr, Elf_Shdr *shdrs,
+			  const char *secstrings, const char *name)
+{
+	/* Section 0 has sh_addr 0. */
+	return (void *)shdrs[find_sec(hdr, shdrs, secstrings, name)].sh_addr;
+}
+
+/* Find a module section, or NULL.  Fill in number of "objects" in section. */
+static void *section_objs(Elf_Ehdr *hdr,
+			  Elf_Shdr *sechdrs,
+			  const char *secstrings,
+			  const char *name,
+			  size_t object_size,
+			  unsigned int *num)
+{
+	unsigned int sec = find_sec(hdr, sechdrs, secstrings, name);
+
+	/* Section 0 has sh_addr 0 and sh_size 0. */
+	*num = sechdrs[sec].sh_size / object_size;
+	return (void *)sechdrs[sec].sh_addr;
+}
+
 /* Provided by the linker */
 extern const struct kernel_symbol __start___ksymtab[];
 extern const struct kernel_symbol __stop___ksymtab[];
@@ -1789,32 +1812,20 @@ static inline void add_kallsyms(struct module *mod,
 }
 #endif /* CONFIG_KALLSYMS */
 
+static void dynamic_printk_setup(struct mod_debug *debug, unsigned int num)
+{
 #ifdef CONFIG_DYNAMIC_PRINTK_DEBUG
-static void dynamic_printk_setup(Elf_Shdr *sechdrs, unsigned int verboseindex)
-{
-	struct mod_debug *debug_info;
-	unsigned long pos, end;
-	unsigned int num_verbose;
+	unsigned int i;
 
-	pos = sechdrs[verboseindex].sh_addr;
-	num_verbose = sechdrs[verboseindex].sh_size /
-				sizeof(struct mod_debug);
-	end = pos + (num_verbose * sizeof(struct mod_debug));
-
-	for (; pos < end; pos += sizeof(struct mod_debug)) {
-		debug_info = (struct mod_debug *)pos;
-		register_dynamic_debug_module(debug_info->modname,
-			debug_info->type, debug_info->logical_modname,
-			debug_info->flag_names, debug_info->hash,
-			debug_info->hash2);
+	for (i = 0; i < num; i++) {
+		register_dynamic_debug_module(debug[i].modname,
+					      debug[i].type,
+					      debug[i].logical_modname,
+					      debug[i].flag_names,
+					      debug[i].hash, debug[i].hash2);
 	}
-}
-#else
-static inline void dynamic_printk_setup(Elf_Shdr *sechdrs,
-					unsigned int verboseindex)
-{
-}
 #endif /* CONFIG_DYNAMIC_PRINTK_DEBUG */
+}
 
 static void *module_alloc_update_bounds(unsigned long size)
 {
@@ -1843,37 +1854,14 @@ static noinline struct module *load_module(void __user *umod,
 	unsigned int i;
 	unsigned int symindex = 0;
 	unsigned int strindex = 0;
-	unsigned int setupindex;
-	unsigned int exindex;
-	unsigned int exportindex;
-	unsigned int modindex;
-	unsigned int obsparmindex;
-	unsigned int infoindex;
-	unsigned int gplindex;
-	unsigned int crcindex;
-	unsigned int gplcrcindex;
-	unsigned int versindex;
-	unsigned int pcpuindex;
-	unsigned int gplfutureindex;
-	unsigned int gplfuturecrcindex;
+	unsigned int modindex, versindex, infoindex, pcpuindex;
 	unsigned int unwindex = 0;
-#ifdef CONFIG_UNUSED_SYMBOLS
-	unsigned int unusedindex;
-	unsigned int unusedcrcindex;
-	unsigned int unusedgplindex;
-	unsigned int unusedgplcrcindex;
-#endif
-	unsigned int markersindex;
-	unsigned int markersstringsindex;
-	unsigned int verboseindex;
-	unsigned int tracepointsindex;
-	unsigned int tracepointsstringsindex;
-	unsigned int mcountindex;
+	unsigned int num_kp, num_mcount;
+	struct kernel_param *kp;
 	struct module *mod;
 	long err = 0;
 	void *percpu = NULL, *ptr = NULL; /* Stops spurious gcc warning */
-	void *mseg;
-	struct exception_table_entry *extable;
+	unsigned long *mseg;
 	mm_segment_t old_fs;
 
 	DEBUGP("load_module: umod=%p, len=%lu, uargs=%p\n",
@@ -1937,6 +1925,7 @@ static noinline struct module *load_module(void __user *umod,
 		err = -ENOEXEC;
 		goto free_hdr;
 	}
+	/* This is temporary: point mod into copy of data. */
 	mod = (void *)sechdrs[modindex].sh_addr;
 
 	if (symindex == 0) {
@@ -1946,22 +1935,6 @@ static noinline struct module *load_module(void __user *umod,
 		goto free_hdr;
 	}
 
-	/* Optional sections */
-	exportindex = find_sec(hdr, sechdrs, secstrings, "__ksymtab");
-	gplindex = find_sec(hdr, sechdrs, secstrings, "__ksymtab_gpl");
-	gplfutureindex = find_sec(hdr, sechdrs, secstrings, "__ksymtab_gpl_future");
-	crcindex = find_sec(hdr, sechdrs, secstrings, "__kcrctab");
-	gplcrcindex = find_sec(hdr, sechdrs, secstrings, "__kcrctab_gpl");
-	gplfuturecrcindex = find_sec(hdr, sechdrs, secstrings, "__kcrctab_gpl_future");
-#ifdef CONFIG_UNUSED_SYMBOLS
-	unusedindex = find_sec(hdr, sechdrs, secstrings, "__ksymtab_unused");
-	unusedgplindex = find_sec(hdr, sechdrs, secstrings, "__ksymtab_unused_gpl");
-	unusedcrcindex = find_sec(hdr, sechdrs, secstrings, "__kcrctab_unused");
-	unusedgplcrcindex = find_sec(hdr, sechdrs, secstrings, "__kcrctab_unused_gpl");
-#endif
-	setupindex = find_sec(hdr, sechdrs, secstrings, "__param");
-	exindex = find_sec(hdr, sechdrs, secstrings, "__ex_table");
-	obsparmindex = find_sec(hdr, sechdrs, secstrings, "__obsparm");
 	versindex = find_sec(hdr, sechdrs, secstrings, "__versions");
 	infoindex = find_sec(hdr, sechdrs, secstrings, ".modinfo");
 	pcpuindex = find_pcpusec(hdr, sechdrs, secstrings);
@@ -2117,42 +2090,57 @@ static noinline struct module *load_module(void __user *umod,
 	if (err < 0)
 		goto cleanup;
 
-	/* Set up EXPORTed & EXPORT_GPLed symbols (section 0 is 0 length) */
-	mod->num_syms = sechdrs[exportindex].sh_size / sizeof(*mod->syms);
-	mod->syms = (void *)sechdrs[exportindex].sh_addr;
-	if (crcindex)
-		mod->crcs = (void *)sechdrs[crcindex].sh_addr;
-	mod->num_gpl_syms = sechdrs[gplindex].sh_size / sizeof(*mod->gpl_syms);
-	mod->gpl_syms = (void *)sechdrs[gplindex].sh_addr;
-	if (gplcrcindex)
-		mod->gpl_crcs = (void *)sechdrs[gplcrcindex].sh_addr;
-	mod->num_gpl_future_syms = sechdrs[gplfutureindex].sh_size /
-					sizeof(*mod->gpl_future_syms);
-	mod->gpl_future_syms = (void *)sechdrs[gplfutureindex].sh_addr;
-	if (gplfuturecrcindex)
-		mod->gpl_future_crcs = (void *)sechdrs[gplfuturecrcindex].sh_addr;
+	/* Now we've got everything in the final locations, we can
+	 * find optional sections. */
+	kp = section_objs(hdr, sechdrs, secstrings, "__param", sizeof(*kp),
+			  &num_kp);
+	mod->syms = section_objs(hdr, sechdrs, secstrings, "__ksymtab",
+				 sizeof(*mod->syms), &mod->num_syms);
+	mod->crcs = section_addr(hdr, sechdrs, secstrings, "__kcrctab");
+	mod->gpl_syms = section_objs(hdr, sechdrs, secstrings, "__ksymtab_gpl",
+				     sizeof(*mod->gpl_syms),
+				     &mod->num_gpl_syms);
+	mod->gpl_crcs = section_addr(hdr, sechdrs, secstrings, "__kcrctab_gpl");
+	mod->gpl_future_syms = section_objs(hdr, sechdrs, secstrings,
+					    "__ksymtab_gpl_future",
+					    sizeof(*mod->gpl_future_syms),
+					    &mod->num_gpl_future_syms);
+	mod->gpl_future_crcs = section_addr(hdr, sechdrs, secstrings,
+					    "__kcrctab_gpl_future");
 
 #ifdef CONFIG_UNUSED_SYMBOLS
-	mod->num_unused_syms = sechdrs[unusedindex].sh_size /
-					sizeof(*mod->unused_syms);
-	mod->num_unused_gpl_syms = sechdrs[unusedgplindex].sh_size /
-					sizeof(*mod->unused_gpl_syms);
-	mod->unused_syms = (void *)sechdrs[unusedindex].sh_addr;
-	if (unusedcrcindex)
-		mod->unused_crcs = (void *)sechdrs[unusedcrcindex].sh_addr;
-	mod->unused_gpl_syms = (void *)sechdrs[unusedgplindex].sh_addr;
-	if (unusedgplcrcindex)
-		mod->unused_gpl_crcs
-			= (void *)sechdrs[unusedgplcrcindex].sh_addr;
+	mod->unused_syms = section_objs(hdr, sechdrs, secstrings,
+					"__ksymtab_unused",
+					sizeof(*mod->unused_syms),
+					&mod->num_unused_syms);
+	mod->unused_crcs = section_addr(hdr, sechdrs, secstrings,
+					"__kcrctab_unused");
+	mod->unused_gpl_syms = section_objs(hdr, sechdrs, secstrings,
+					    "__ksymtab_unused_gpl",
+					    sizeof(*mod->unused_gpl_syms),
+					    &mod->num_unused_gpl_syms);
+	mod->unused_gpl_crcs = section_addr(hdr, sechdrs, secstrings,
+					    "__kcrctab_unused_gpl");
+#endif
+
+#ifdef CONFIG_MARKERS
+	mod->markers = section_objs(hdr, sechdrs, secstrings, "__markers",
+				    sizeof(*mod->markers), &mod->num_markers);
+#endif
+#ifdef CONFIG_TRACEPOINTS
+	mod->tracepoints = section_objs(hdr, sechdrs, secstrings,
+					"__tracepoints",
+					sizeof(*mod->tracepoints),
+					&mod->num_tracepoints);
 #endif
 
 #ifdef CONFIG_MODVERSIONS
-	if ((mod->num_syms && !crcindex)
-	    || (mod->num_gpl_syms && !gplcrcindex)
-	    || (mod->num_gpl_future_syms && !gplfuturecrcindex)
+	if ((mod->num_syms && !mod->crcs)
+	    || (mod->num_gpl_syms && !mod->gpl_crcs)
+	    || (mod->num_gpl_future_syms && !mod->gpl_future_crcs)
 #ifdef CONFIG_UNUSED_SYMBOLS
-	    || (mod->num_unused_syms && !unusedcrcindex)
-	    || (mod->num_unused_gpl_syms && !unusedgplcrcindex)
+	    || (mod->num_unused_syms && !mod->unused_crcs)
+	    || (mod->num_unused_gpl_syms && !mod->unused_gpl_crcs)
 #endif
 		) {
 		printk(KERN_WARNING "%s: No versions for exported symbols.\n", mod->name);
@@ -2161,16 +2149,6 @@ static noinline struct module *load_module(void __user *umod,
 			goto cleanup;
 	}
 #endif
-	markersindex = find_sec(hdr, sechdrs, secstrings, "__markers");
- 	markersstringsindex = find_sec(hdr, sechdrs, secstrings,
-					"__markers_strings");
-	verboseindex = find_sec(hdr, sechdrs, secstrings, "__verbose");
-	tracepointsindex = find_sec(hdr, sechdrs, secstrings, "__tracepoints");
-	tracepointsstringsindex = find_sec(hdr, sechdrs, secstrings,
-					"__tracepoints_strings");
-
-	mcountindex = find_sec(hdr, sechdrs, secstrings,
-			       "__mcount_loc");
 
 	/* Now do relocations. */
 	for (i = 1; i < hdr->e_shnum; i++) {
@@ -2193,28 +2171,16 @@ static noinline struct module *load_module(void __user *umod,
 		if (err < 0)
 			goto cleanup;
 	}
-#ifdef CONFIG_MARKERS
-	mod->markers = (void *)sechdrs[markersindex].sh_addr;
-	mod->num_markers =
-		sechdrs[markersindex].sh_size / sizeof(*mod->markers);
-#endif
-#ifdef CONFIG_TRACEPOINTS
-	mod->tracepoints = (void *)sechdrs[tracepointsindex].sh_addr;
-	mod->num_tracepoints =
-		sechdrs[tracepointsindex].sh_size / sizeof(*mod->tracepoints);
-#endif
-
 
         /* Find duplicate symbols */
 	err = verify_export_symbols(mod);
-
 	if (err < 0)
 		goto cleanup;
 
   	/* Set up and sort exception table */
-	mod->num_exentries = sechdrs[exindex].sh_size / sizeof(*mod->extable);
-	mod->extable = extable = (void *)sechdrs[exindex].sh_addr;
-	sort_extable(extable, extable + mod->num_exentries);
+	mod->extable = section_objs(hdr, sechdrs, secstrings, "__ex_table",
+				    sizeof(*mod->extable), &mod->num_exentries);
+	sort_extable(mod->extable, mod->extable + mod->num_exentries);
 
 	/* Finally, copy percpu area over. */
 	percpu_modcopy(mod->percpu, (void *)sechdrs[pcpuindex].sh_addr,
@@ -2223,11 +2189,17 @@ static noinline struct module *load_module(void __user *umod,
 	add_kallsyms(mod, sechdrs, symindex, strindex, secstrings);
 
 	if (!mod->taints) {
+		struct mod_debug *debug;
+		unsigned int num_debug;
+
 #ifdef CONFIG_MARKERS
 		marker_update_probe_range(mod->markers,
 			mod->markers + mod->num_markers);
 #endif
-	dynamic_printk_setup(sechdrs, verboseindex);
+		debug = section_objs(hdr, sechdrs, secstrings, "__verbose",
+				     sizeof(*debug), &num_debug);
+		dynamic_printk_setup(debug, num_debug);
+
 #ifdef CONFIG_TRACEPOINTS
 		tracepoint_update_probe_range(mod->tracepoints,
 			mod->tracepoints + mod->num_tracepoints);
@@ -2235,8 +2207,9 @@ static noinline struct module *load_module(void __user *umod,
 	}
 
 	/* sechdrs[0].sh_size is always zero */
-	mseg = (void *)sechdrs[mcountindex].sh_addr;
-	ftrace_init_module(mseg, mseg + sechdrs[mcountindex].sh_size);
+	mseg = section_objs(hdr, sechdrs, secstrings, "__mcount_loc",
+			    sizeof(*mseg), &num_mcount);
+	ftrace_init_module(mseg, mseg + num_mcount);
 
 	err = module_finalize(hdr, sechdrs, mod);
 	if (err < 0)
@@ -2261,7 +2234,7 @@ static noinline struct module *load_module(void __user *umod,
 	set_fs(old_fs);
 
 	mod->args = args;
-	if (obsparmindex)
+	if (section_addr(hdr, sechdrs, secstrings, "__obsparm"))
 		printk(KERN_WARNING "%s: Ignoring obsolete parameters\n",
 		       mod->name);
 
@@ -2270,21 +2243,11 @@ static noinline struct module *load_module(void __user *umod,
          * strong_try_module_get() will fail. */
 	stop_machine(__link_module, mod, NULL);
 
-	/* Size of section 0 is 0, so this works well if no params */
-	err = parse_args(mod->name, mod->args,
-			 (struct kernel_param *)
-			 sechdrs[setupindex].sh_addr,
-			 sechdrs[setupindex].sh_size
-			 / sizeof(struct kernel_param),
-			 NULL);
+	err = parse_args(mod->name, mod->args, kp, num_kp, NULL);
 	if (err < 0)
 		goto unlink;
 
-	err = mod_sysfs_setup(mod,
-			      (struct kernel_param *)
-			      sechdrs[setupindex].sh_addr,
-			      sechdrs[setupindex].sh_size
-			      / sizeof(struct kernel_param));
+	err = mod_sysfs_setup(mod, kp, num_kp);
 	if (err < 0)
 		goto unlink;
 	add_sect_attrs(mod, hdr->e_shnum, secstrings, sechdrs);

From d72b37513cdfbd3f53f3d485a8c403cc96d2c95f Mon Sep 17 00:00:00 2001
From: Andi Kleen <andi@firstfloor.org>
Date: Sat, 30 Aug 2008 10:09:00 +0200
Subject: [PATCH 02/11] Remove stop_machine during module load v2

Remove stop_machine during module load v2

module loading currently does a stop_machine on each module load to insert
the module into the global module lists.  Especially on larger systems this
can be quite expensive.

It does that to handle concurrent lock lessmodule list readers
like kallsyms.

I don't think stop_machine() is actually needed to insert something
into a list though. There are no concurrent writers because the
module mutex is taken. And the RCU list functions know how to insert
a node into a list with the right memory ordering so that concurrent
readers don't go off into the wood.

So remove the stop_machine for the module list insert and just
do a list_add_rcu() instead.

Module removal will still do a stop_machine of course, it needs
that for other reasons.

v2: Revised readers based on Paul's comments. All readers that only
    rely on disabled preemption need to be changed to list_for_each_rcu().
    Done that. The others are ok because they have the modules mutex.
    Also added a possible missing preempt disable for print_modules().

[cc Paul McKenney for review. It's not RCU, but quite similar.]

Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 kernel/module.c | 47 ++++++++++++++++++++++-------------------------
 1 file changed, 22 insertions(+), 25 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index 3d256681ab64..c0f1826e2d9e 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -42,6 +42,7 @@
 #include <linux/string.h>
 #include <linux/mutex.h>
 #include <linux/unwind.h>
+#include <linux/rculist.h>
 #include <asm/uaccess.h>
 #include <asm/cacheflush.h>
 #include <linux/license.h>
@@ -63,7 +64,7 @@
 #define INIT_OFFSET_MASK (1UL << (BITS_PER_LONG-1))
 
 /* List of modules, protected by module_mutex or preempt_disable
- * (add/delete uses stop_machine). */
+ * (delete uses stop_machine/add uses RCU list operations). */
 static DEFINE_MUTEX(module_mutex);
 static LIST_HEAD(modules);
 
@@ -241,7 +242,7 @@ static bool each_symbol(bool (*fn)(const struct symsearch *arr,
 	if (each_symbol_in_section(arr, ARRAY_SIZE(arr), NULL, fn, data))
 		return true;
 
-	list_for_each_entry(mod, &modules, list) {
+	list_for_each_entry_rcu(mod, &modules, list) {
 		struct symsearch arr[] = {
 			{ mod->syms, mod->syms + mod->num_syms, mod->crcs,
 			  NOT_GPL_ONLY, false },
@@ -1416,17 +1417,6 @@ static void mod_kobject_remove(struct module *mod)
 	mod_sysfs_fini(mod);
 }
 
-/*
- * link the module with the whole machine is stopped with interrupts off
- * - this defends against kallsyms not taking locks
- */
-static int __link_module(void *_mod)
-{
-	struct module *mod = _mod;
-	list_add(&mod->list, &modules);
-	return 0;
-}
-
 /*
  * unlink the module with the whole machine is stopped with interrupts off
  * - this defends against kallsyms not taking locks
@@ -2239,9 +2229,13 @@ static noinline struct module *load_module(void __user *umod,
 		       mod->name);
 
 	/* Now sew it into the lists so we can get lockdep and oops
-         * info during argument parsing.  Noone should access us, since
-         * strong_try_module_get() will fail. */
-	stop_machine(__link_module, mod, NULL);
+	 * info during argument parsing.  Noone should access us, since
+	 * strong_try_module_get() will fail.
+	 * lockdep/oops can run asynchronous, so use the RCU list insertion
+	 * function to insert in a way safe to concurrent readers.
+	 * The mutex protects against concurrent writers.
+	 */
+	list_add_rcu(&mod->list, &modules);
 
 	err = parse_args(mod->name, mod->args, kp, num_kp, NULL);
 	if (err < 0)
@@ -2436,7 +2430,7 @@ const char *module_address_lookup(unsigned long addr,
 	const char *ret = NULL;
 
 	preempt_disable();
-	list_for_each_entry(mod, &modules, list) {
+	list_for_each_entry_rcu(mod, &modules, list) {
 		if (within(addr, mod->module_init, mod->init_size)
 		    || within(addr, mod->module_core, mod->core_size)) {
 			if (modname)
@@ -2459,7 +2453,7 @@ int lookup_module_symbol_name(unsigned long addr, char *symname)
 	struct module *mod;
 
 	preempt_disable();
-	list_for_each_entry(mod, &modules, list) {
+	list_for_each_entry_rcu(mod, &modules, list) {
 		if (within(addr, mod->module_init, mod->init_size) ||
 		    within(addr, mod->module_core, mod->core_size)) {
 			const char *sym;
@@ -2483,7 +2477,7 @@ int lookup_module_symbol_attrs(unsigned long addr, unsigned long *size,
 	struct module *mod;
 
 	preempt_disable();
-	list_for_each_entry(mod, &modules, list) {
+	list_for_each_entry_rcu(mod, &modules, list) {
 		if (within(addr, mod->module_init, mod->init_size) ||
 		    within(addr, mod->module_core, mod->core_size)) {
 			const char *sym;
@@ -2510,7 +2504,7 @@ int module_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
 	struct module *mod;
 
 	preempt_disable();
-	list_for_each_entry(mod, &modules, list) {
+	list_for_each_entry_rcu(mod, &modules, list) {
 		if (symnum < mod->num_symtab) {
 			*value = mod->symtab[symnum].st_value;
 			*type = mod->symtab[symnum].st_info;
@@ -2553,7 +2547,7 @@ unsigned long module_kallsyms_lookup_name(const char *name)
 			ret = mod_find_symname(mod, colon+1);
 		*colon = ':';
 	} else {
-		list_for_each_entry(mod, &modules, list)
+		list_for_each_entry_rcu(mod, &modules, list)
 			if ((ret = mod_find_symname(mod, name)) != 0)
 				break;
 	}
@@ -2656,7 +2650,7 @@ const struct exception_table_entry *search_module_extables(unsigned long addr)
 	struct module *mod;
 
 	preempt_disable();
-	list_for_each_entry(mod, &modules, list) {
+	list_for_each_entry_rcu(mod, &modules, list) {
 		if (mod->num_exentries == 0)
 			continue;
 
@@ -2682,7 +2676,7 @@ int is_module_address(unsigned long addr)
 
 	preempt_disable();
 
-	list_for_each_entry(mod, &modules, list) {
+	list_for_each_entry_rcu(mod, &modules, list) {
 		if (within(addr, mod->module_core, mod->core_size)) {
 			preempt_enable();
 			return 1;
@@ -2703,7 +2697,7 @@ struct module *__module_text_address(unsigned long addr)
 	if (addr < module_addr_min || addr > module_addr_max)
 		return NULL;
 
-	list_for_each_entry(mod, &modules, list)
+	list_for_each_entry_rcu(mod, &modules, list)
 		if (within(addr, mod->module_init, mod->init_text_size)
 		    || within(addr, mod->module_core, mod->core_text_size))
 			return mod;
@@ -2728,8 +2722,11 @@ void print_modules(void)
 	char buf[8];
 
 	printk("Modules linked in:");
-	list_for_each_entry(mod, &modules, list)
+	/* Most callers should already have preempt disabled, but make sure */
+	preempt_disable();
+	list_for_each_entry_rcu(mod, &modules, list)
 		printk(" %s%s", mod->name, module_flags(mod, buf));
+	preempt_enable();
 	if (last_unloaded_module[0])
 		printk(" [last unloaded: %s]", last_unloaded_module);
 	printk("\n");

From 730b69d225259565c705f5f5a11cb1aba69568f1 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Wed, 22 Oct 2008 10:00:22 -0500
Subject: [PATCH 03/11] module: check kernel param length at compile time, not
 runtime

The kparam code tries to handle over-length parameter prefixes at
runtime.  Not only would I bet this has never been tested, it's not
clear that truncating names is a good idea either.

So let's check at compile time.  We need to move the #define to
moduleparam.h to do this, though.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 include/linux/module.h      | 2 +-
 include/linux/moduleparam.h | 6 +++++-
 kernel/params.c             | 7 ++-----
 3 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/include/linux/module.h b/include/linux/module.h
index eddf27db442b..196b499270da 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -29,7 +29,7 @@
 #define MODULE_SYMBOL_PREFIX ""
 #endif
 
-#define MODULE_NAME_LEN (64 - sizeof(unsigned long))
+#define MODULE_NAME_LEN MAX_PARAM_PREFIX_LEN
 
 struct kernel_symbol
 {
diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index ec624381c844..1eefe6d61b86 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -13,6 +13,9 @@
 #define MODULE_PARAM_PREFIX KBUILD_MODNAME "."
 #endif
 
+/* Chosen so that structs with an unsigned long line up. */
+#define MAX_PARAM_PREFIX_LEN (64 - sizeof(unsigned long))
+
 #ifdef MODULE
 #define ___module_cat(a,b) __mod_ ## a ## b
 #define __module_cat(a,b) ___module_cat(a,b)
@@ -79,7 +82,8 @@ struct kparam_array
 #define __module_param_call(prefix, name, set, get, arg, perm)		\
 	/* Default value instead of permissions? */			\
 	static int __param_perm_check_##name __attribute__((unused)) =	\
-	BUILD_BUG_ON_ZERO((perm) < 0 || (perm) > 0777 || ((perm) & 2));	\
+	BUILD_BUG_ON_ZERO((perm) < 0 || (perm) > 0777 || ((perm) & 2))	\
+	+ BUILD_BUG_ON_ZERO(sizeof(""prefix) > MAX_PARAM_PREFIX_LEN);	\
 	static const char __param_str_##name[] = prefix #name;		\
 	static struct kernel_param __moduleparam_const __param_##name	\
 	__used								\
diff --git a/kernel/params.c b/kernel/params.c
index afc46a23eb6d..aca07e1a050f 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -585,17 +585,14 @@ static void __init param_sysfs_builtin(void)
 {
 	struct kernel_param *kp, *kp_begin = NULL;
 	unsigned int i, name_len, count = 0;
-	char modname[MODULE_NAME_LEN + 1] = "";
+	char modname[MODULE_NAME_LEN] = "";
 
 	for (i=0; i < __stop___param - __start___param; i++) {
 		char *dot;
-		size_t max_name_len;
 
 		kp = &__start___param[i];
-		max_name_len =
-			min_t(size_t, MODULE_NAME_LEN, strlen(kp->name));
 
-		dot = memchr(kp->name, '.', max_name_len);
+		dot = strchr(kp->name, '.');
 		if (!dot) {
 			DEBUGP("couldn't find period in first %d characters "
 			       "of %s\n", MODULE_NAME_LEN, kp->name);

From 9b473de87209fa86eb421b23386693b461612f30 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Wed, 22 Oct 2008 10:00:22 -0500
Subject: [PATCH 04/11] param: Fix duplicate module prefixes

Instead of insisting each new module_param sysfs entry is unique,
handle the case where it already exists (for builtin modules).

The current code assumes that all identical prefixes are together in
the section: true for normal uses, but not necessarily so if someone
overrides MODULE_PARAM_PREFIX.  More importantly, it's not true with
the new "core_param()" code which uses "kernel" as a prefix.

This simplifies the caller for the builtin case, at a slight loss of
efficiency (we do the lookup every time to see if the directory
exists).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
---
 include/linux/module.h |   2 +-
 kernel/params.c        | 259 ++++++++++++++++++++++-------------------
 2 files changed, 141 insertions(+), 120 deletions(-)

diff --git a/include/linux/module.h b/include/linux/module.h
index 196b499270da..3bfed013350b 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -60,6 +60,7 @@ struct module_kobject
 	struct kobject kobj;
 	struct module *mod;
 	struct kobject *drivers_dir;
+	struct module_param_attrs *mp;
 };
 
 /* These are either module local, or the kernel's dummy ones. */
@@ -242,7 +243,6 @@ struct module
 
 	/* Sysfs stuff. */
 	struct module_kobject mkobj;
-	struct module_param_attrs *param_attrs;
 	struct module_attribute *modinfo_attrs;
 	const char *version;
 	const char *srcversion;
diff --git a/kernel/params.c b/kernel/params.c
index aca07e1a050f..f27c992a4625 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -373,6 +373,8 @@ int param_get_string(char *buffer, struct kernel_param *kp)
 }
 
 /* sysfs output in /sys/modules/XYZ/parameters/ */
+#define to_module_attr(n) container_of(n, struct module_attribute, attr);
+#define to_module_kobject(n) container_of(n, struct module_kobject, kobj);
 
 extern struct kernel_param __start___param[], __stop___param[];
 
@@ -384,6 +386,7 @@ struct param_attribute
 
 struct module_param_attrs
 {
+	unsigned int num;
 	struct attribute_group grp;
 	struct param_attribute attrs[0];
 };
@@ -434,69 +437,84 @@ static ssize_t param_attr_store(struct module_attribute *mattr,
 
 #ifdef CONFIG_SYSFS
 /*
- * param_sysfs_setup - setup sysfs support for one module or KBUILD_MODNAME
- * @mk: struct module_kobject (contains parent kobject)
- * @kparam: array of struct kernel_param, the actual parameter definitions
- * @num_params: number of entries in array
- * @name_skip: offset where the parameter name start in kparam[].name. Needed for built-in "modules"
+ * add_sysfs_param - add a parameter to sysfs
+ * @mk: struct module_kobject
+ * @kparam: the actual parameter definition to add to sysfs
+ * @name: name of parameter
  *
- * Create a kobject for a (per-module) group of parameters, and create files
- * in sysfs. A pointer to the param_kobject is returned on success,
- * NULL if there's no parameter to export, or other ERR_PTR(err).
+ * Create a kobject if for a (per-module) parameter if mp NULL, and
+ * create file in sysfs.  Returns an error on out of memory.  Always cleans up
+ * if there's an error.
  */
-static __modinit struct module_param_attrs *
-param_sysfs_setup(struct module_kobject *mk,
-		  struct kernel_param *kparam,
-		  unsigned int num_params,
-		  unsigned int name_skip)
+static __modinit int add_sysfs_param(struct module_kobject *mk,
+				     struct kernel_param *kp,
+				     const char *name)
 {
-	struct module_param_attrs *mp;
-	unsigned int valid_attrs = 0;
-	unsigned int i, size[2];
-	struct param_attribute *pattr;
-	struct attribute **gattr;
-	int err;
+	struct module_param_attrs *new;
+	struct attribute **attrs;
+	int err, num;
 
-	for (i=0; i<num_params; i++) {
-		if (kparam[i].perm)
-			valid_attrs++;
+	/* We don't bother calling this with invisible parameters. */
+	BUG_ON(!kp->perm);
+
+	if (!mk->mp) {
+		num = 0;
+		attrs = NULL;
+	} else {
+		num = mk->mp->num;
+		attrs = mk->mp->grp.attrs;
 	}
 
-	if (!valid_attrs)
-		return NULL;
-
-	size[0] = ALIGN(sizeof(*mp) +
-			valid_attrs * sizeof(mp->attrs[0]),
-			sizeof(mp->grp.attrs[0]));
-	size[1] = (valid_attrs + 1) * sizeof(mp->grp.attrs[0]);
-
-	mp = kzalloc(size[0] + size[1], GFP_KERNEL);
-	if (!mp)
-		return ERR_PTR(-ENOMEM);
-
-	mp->grp.name = "parameters";
-	mp->grp.attrs = (void *)mp + size[0];
-
-	pattr = &mp->attrs[0];
-	gattr = &mp->grp.attrs[0];
-	for (i = 0; i < num_params; i++) {
-		struct kernel_param *kp = &kparam[i];
-		if (kp->perm) {
-			pattr->param = kp;
-			pattr->mattr.show = param_attr_show;
-			pattr->mattr.store = param_attr_store;
-			pattr->mattr.attr.name = (char *)&kp->name[name_skip];
-			pattr->mattr.attr.mode = kp->perm;
-			*(gattr++) = &(pattr++)->mattr.attr;
-		}
+	/* Enlarge. */
+	new = krealloc(mk->mp,
+		       sizeof(*mk->mp) + sizeof(mk->mp->attrs[0]) * (num+1),
+		       GFP_KERNEL);
+	if (!new) {
+		kfree(mk->mp);
+		err = -ENOMEM;
+		goto fail;
 	}
-	*gattr = NULL;
-
-	if ((err = sysfs_create_group(&mk->kobj, &mp->grp))) {
-		kfree(mp);
-		return ERR_PTR(err);
+	attrs = krealloc(attrs, sizeof(new->grp.attrs[0])*(num+2), GFP_KERNEL);
+	if (!attrs) {
+		err = -ENOMEM;
+		goto fail_free_new;
 	}
-	return mp;
+
+	/* Sysfs wants everything zeroed. */
+	memset(new, 0, sizeof(*new));
+	memset(&new->attrs[num], 0, sizeof(new->attrs[num]));
+	memset(&attrs[num], 0, sizeof(attrs[num]));
+	new->grp.name = "parameters";
+	new->grp.attrs = attrs;
+
+	/* Tack new one on the end. */
+	new->attrs[num].param = kp;
+	new->attrs[num].mattr.show = param_attr_show;
+	new->attrs[num].mattr.store = param_attr_store;
+	new->attrs[num].mattr.attr.name = (char *)name;
+	new->attrs[num].mattr.attr.mode = kp->perm;
+	new->num = num+1;
+
+	/* Fix up all the pointers, since krealloc can move us */
+	for (num = 0; num < new->num; num++)
+		new->grp.attrs[num] = &new->attrs[num].mattr.attr;
+	new->grp.attrs[num] = NULL;
+
+	mk->mp = new;
+	return 0;
+
+fail_free_new:
+	kfree(new);
+fail:
+	mk->mp = NULL;
+	return err;
+}
+
+static void free_module_param_attrs(struct module_kobject *mk)
+{
+	kfree(mk->mp->grp.attrs);
+	kfree(mk->mp);
+	mk->mp = NULL;
 }
 
 #ifdef CONFIG_MODULES
@@ -506,21 +524,33 @@ param_sysfs_setup(struct module_kobject *mk,
  * @kparam: module parameters (array)
  * @num_params: number of module parameters
  *
- * Adds sysfs entries for module parameters, and creates a link from
- * /sys/module/[mod->name]/parameters to /sys/parameters/[mod->name]/
+ * Adds sysfs entries for module parameters under
+ * /sys/module/[mod->name]/parameters/
  */
 int module_param_sysfs_setup(struct module *mod,
 			     struct kernel_param *kparam,
 			     unsigned int num_params)
 {
-	struct module_param_attrs *mp;
+	int i, err;
+	bool params = false;
 
-	mp = param_sysfs_setup(&mod->mkobj, kparam, num_params, 0);
-	if (IS_ERR(mp))
-		return PTR_ERR(mp);
+	for (i = 0; i < num_params; i++) {
+		if (kparam[i].perm == 0)
+			continue;
+		err = add_sysfs_param(&mod->mkobj, &kparam[i], kparam[i].name);
+		if (err)
+			return err;
+		params = true;
+	}
 
-	mod->param_attrs = mp;
-	return 0;
+	if (!params)
+		return 0;
+
+	/* Create the param group. */
+	err = sysfs_create_group(&mod->mkobj.kobj, &mod->mkobj.mp->grp);
+	if (err)
+		free_module_param_attrs(&mod->mkobj);
+	return err;
 }
 
 /*
@@ -532,43 +562,55 @@ int module_param_sysfs_setup(struct module *mod,
  */
 void module_param_sysfs_remove(struct module *mod)
 {
-	if (mod->param_attrs) {
-		sysfs_remove_group(&mod->mkobj.kobj,
-				   &mod->param_attrs->grp);
+	if (mod->mkobj.mp) {
+		sysfs_remove_group(&mod->mkobj.kobj, &mod->mkobj.mp->grp);
 		/* We are positive that no one is using any param
 		 * attrs at this point.  Deallocate immediately. */
-		kfree(mod->param_attrs);
-		mod->param_attrs = NULL;
+		free_module_param_attrs(&mod->mkobj);
 	}
 }
 #endif
 
-/*
- * kernel_param_sysfs_setup - wrapper for built-in params support
- */
-static void __init kernel_param_sysfs_setup(const char *name,
-					    struct kernel_param *kparam,
-					    unsigned int num_params,
-					    unsigned int name_skip)
+static void __init kernel_add_sysfs_param(const char *name,
+					  struct kernel_param *kparam,
+					  unsigned int name_skip)
 {
 	struct module_kobject *mk;
-	int ret;
+	struct kobject *kobj;
+	int err;
 
-	mk = kzalloc(sizeof(struct module_kobject), GFP_KERNEL);
-	BUG_ON(!mk);
+	kobj = kset_find_obj(module_kset, name);
+	if (kobj) {
+		/* We already have one.  Remove params so we can add more. */
+		mk = to_module_kobject(kobj);
+		/* We need to remove it before adding parameters. */
+		sysfs_remove_group(&mk->kobj, &mk->mp->grp);
+	} else {
+		mk = kzalloc(sizeof(struct module_kobject), GFP_KERNEL);
+		BUG_ON(!mk);
 
-	mk->mod = THIS_MODULE;
-	mk->kobj.kset = module_kset;
-	ret = kobject_init_and_add(&mk->kobj, &module_ktype, NULL, "%s", name);
-	if (ret) {
-		kobject_put(&mk->kobj);
-		printk(KERN_ERR "Module '%s' failed to be added to sysfs, "
-		      "error number %d\n", name, ret);
-		printk(KERN_ERR	"The system will be unstable now.\n");
-		return;
+		mk->mod = THIS_MODULE;
+		mk->kobj.kset = module_kset;
+		err = kobject_init_and_add(&mk->kobj, &module_ktype, NULL,
+					   "%s", name);
+		if (err) {
+			kobject_put(&mk->kobj);
+			printk(KERN_ERR "Module '%s' failed add to sysfs, "
+			       "error number %d\n", name, err);
+			printk(KERN_ERR	"The system will be unstable now.\n");
+			return;
+		}
+		/* So that exit path is even. */
+		kobject_get(&mk->kobj);
 	}
-	param_sysfs_setup(mk, kparam, num_params, name_skip);
+
+	/* These should not fail at boot. */
+	err = add_sysfs_param(mk, kparam, kparam->name + name_skip);
+	BUG_ON(err);
+	err = sysfs_create_group(&mk->kobj, &mk->mp->grp);
+	BUG_ON(err);
 	kobject_uevent(&mk->kobj, KOBJ_ADD);
+	kobject_put(&mk->kobj);
 }
 
 /*
@@ -579,18 +621,19 @@ static void __init kernel_param_sysfs_setup(const char *name,
  * The "module" name (KBUILD_MODNAME) is stored before a dot, the
  * "parameter" name is stored behind a dot in kernel_param->name. So,
  * extract the "module" name for all built-in kernel_param-eters,
- * and for all who have the same, call kernel_param_sysfs_setup.
+ * and for all who have the same, call kernel_add_sysfs_param.
  */
 static void __init param_sysfs_builtin(void)
 {
-	struct kernel_param *kp, *kp_begin = NULL;
-	unsigned int i, name_len, count = 0;
-	char modname[MODULE_NAME_LEN] = "";
+	struct kernel_param *kp;
+	unsigned int name_len;
+	char modname[MODULE_NAME_LEN];
 
-	for (i=0; i < __stop___param - __start___param; i++) {
+	for (kp = __start___param; kp < __stop___param; kp++) {
 		char *dot;
 
-		kp = &__start___param[i];
+		if (kp->perm == 0)
+			continue;
 
 		dot = strchr(kp->name, '.');
 		if (!dot) {
@@ -599,37 +642,15 @@ static void __init param_sysfs_builtin(void)
 			continue;
 		}
 		name_len = dot - kp->name;
-
- 		/* new kbuild_modname? */
-		if (strlen(modname) != name_len
-		    || strncmp(modname, kp->name, name_len) != 0) {
-			/* add a new kobject for previous kernel_params. */
-			if (count)
-				kernel_param_sysfs_setup(modname,
-							 kp_begin,
-							 count,
-							 strlen(modname)+1);
-
-			strncpy(modname, kp->name, name_len);
-			modname[name_len] = '\0';
-			count = 0;
-			kp_begin = kp;
-		}
-		count++;
+		strncpy(modname, kp->name, name_len);
+		modname[name_len] = '\0';
+		kernel_add_sysfs_param(modname, kp, name_len+1);
 	}
-
-	/* last kernel_params need to be registered as well */
-	if (count)
-		kernel_param_sysfs_setup(modname, kp_begin, count,
-					 strlen(modname)+1);
 }
 
 
 /* module-related sysfs stuff */
 
-#define to_module_attr(n) container_of(n, struct module_attribute, attr);
-#define to_module_kobject(n) container_of(n, struct module_kobject, kobj);
-
 static ssize_t module_attr_show(struct kobject *kobj,
 				struct attribute *attr,
 				char *buf)

From 67e67ceaac5bf55dbdceb704ff2d763d438b5373 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Wed, 22 Oct 2008 10:00:23 -0500
Subject: [PATCH 05/11] core_param() for genuinely core kernel parameters

There are a lot of one-liner uses of __setup() in the kernel: they're
cumbersome and not queryable (definitely not settable) via /sys.  Yet
it's ugly to simplify them to module_param(), because by default that
inserts a prefix of the module name (usually filename).

So, introduce a "core_param".  The parameter gets no prefix, but
appears in /sys/module/kernel/parameters/ (if non-zero perms arg).  I
thought about using the name "core", but that's more common than
"kernel".  And if you create a module called "kernel", you will die
a horrible death.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 include/linux/moduleparam.h | 19 +++++++++++++++++++
 kernel/params.c             | 14 +++++++-------
 2 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index 1eefe6d61b86..e4af3399ef48 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -104,6 +104,25 @@ struct kparam_array
 #define module_param(name, type, perm)				\
 	module_param_named(name, name, type, perm)
 
+#ifndef MODULE
+/**
+ * core_param - define a historical core kernel parameter.
+ * @name: the name of the cmdline and sysfs parameter (often the same as var)
+ * @var: the variable
+ * @type: the type (for param_set_##type and param_get_##type)
+ * @perm: visibility in sysfs
+ *
+ * core_param is just like module_param(), but cannot be modular and
+ * doesn't add a prefix (such as "printk.").  This is for compatibility
+ * with __setup(), and it makes sense as truly core parameters aren't
+ * tied to the particular file they're in.
+ */
+#define core_param(name, var, type, perm)				\
+	param_check_##type(name, &(var));				\
+	__module_param_call("", name, param_set_##type, param_get_##type, \
+			    &var, perm)
+#endif /* !MODULE */
+
 /* Actually copy string: maxlen param is usually sizeof(string). */
 #define module_param_string(name, string, len, perm)			\
 	static const struct kparam_string __param_string_##name		\
diff --git a/kernel/params.c b/kernel/params.c
index f27c992a4625..b077f1b045d3 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -637,14 +637,14 @@ static void __init param_sysfs_builtin(void)
 
 		dot = strchr(kp->name, '.');
 		if (!dot) {
-			DEBUGP("couldn't find period in first %d characters "
-			       "of %s\n", MODULE_NAME_LEN, kp->name);
-			continue;
+			/* This happens for core_param() */
+			strcpy(modname, "kernel");
+			name_len = 0;
+		} else {
+			name_len = dot - kp->name + 1;
+			strlcpy(modname, kp->name, name_len);
 		}
-		name_len = dot - kp->name;
-		strncpy(modname, kp->name, name_len);
-		modname[name_len] = '\0';
-		kernel_add_sysfs_param(modname, kp, name_len+1);
+		kernel_add_sysfs_param(modname, kp, name_len);
 	}
 }
 

From d0ea3d7d286aeda2a9216d76424abc285b87b7b4 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Wed, 22 Oct 2008 10:00:23 -0500
Subject: [PATCH 06/11] Make initcall_debug a core_param

This is the one I really wanted: now it effects module loading, it
makes sense to be able to flip it after boot.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
---
 init/main.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/init/main.c b/init/main.c
index 3e17a3bafe60..3d68aaaf6160 100644
--- a/init/main.c
+++ b/init/main.c
@@ -697,13 +697,7 @@ asmlinkage void __init start_kernel(void)
 }
 
 static int initcall_debug;
-
-static int __init initcall_debug_setup(char *str)
-{
-	initcall_debug = 1;
-	return 1;
-}
-__setup("initcall_debug", initcall_debug_setup);
+core_param(initcall_debug, initcall_debug, bool, 0644);
 
 int do_one_initcall(initcall_t fn)
 {

From f44dd164f37336f7e17fabf5740698fd10635172 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Wed, 22 Oct 2008 10:00:24 -0500
Subject: [PATCH 07/11] Make panic= and panic_on_oops into core_params

This allows them to be examined and set after boot, plus means they
actually give errors if they are misused (eg. panic=yes).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 kernel/panic.c | 17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/kernel/panic.c b/kernel/panic.c
index bda561ef3cdf..6513aac8e992 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -34,13 +34,6 @@ ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
 
 EXPORT_SYMBOL(panic_notifier_list);
 
-static int __init panic_setup(char *str)
-{
-	panic_timeout = simple_strtoul(str, NULL, 0);
-	return 1;
-}
-__setup("panic=", panic_setup);
-
 static long no_blink(long time)
 {
 	return 0;
@@ -218,13 +211,6 @@ void add_taint(unsigned flag)
 }
 EXPORT_SYMBOL(add_taint);
 
-static int __init pause_on_oops_setup(char *str)
-{
-	pause_on_oops = simple_strtoul(str, NULL, 0);
-	return 1;
-}
-__setup("pause_on_oops=", pause_on_oops_setup);
-
 static void spin_msec(int msecs)
 {
 	int i;
@@ -384,3 +370,6 @@ void __stack_chk_fail(void)
 }
 EXPORT_SYMBOL(__stack_chk_fail);
 #endif
+
+core_param(panic, panic_timeout, int, 0644);
+core_param(pause_on_oops, pause_on_oops, int, 0644);

From a802dd0eb5fc97a50cf1abb1f788a8f6cc5db635 Mon Sep 17 00:00:00 2001
From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Mon, 13 Oct 2008 23:50:08 +0200
Subject: [PATCH 08/11] Call init_workqueues before pre smp initcalls.

This allows to create workqueues from within the context of
a pre smp initcall (aka early_initcall).

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 init/main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/init/main.c b/init/main.c
index 3d68aaaf6160..6c7fd137c8cd 100644
--- a/init/main.c
+++ b/init/main.c
@@ -767,8 +767,6 @@ static void __init do_initcalls(void)
 static void __init do_basic_setup(void)
 {
 	rcu_init_sched(); /* needed by module_init stage. */
-	/* drivers will send hotplug events */
-	init_workqueues();
 	usermodehelper_init();
 	driver_init();
 	init_irq_proc();
@@ -852,6 +850,8 @@ static int __init kernel_init(void * unused)
 
 	cad_pid = task_pid(current);
 
+	init_workqueues();
+
 	smp_prepare_cpus(setup_max_cpus);
 
 	do_pre_smp_initcalls();

From 0d557dc97f4bb501f086a03d0f00b99a7855d794 Mon Sep 17 00:00:00 2001
From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Mon, 13 Oct 2008 23:50:09 +0200
Subject: [PATCH 09/11] workqueue: introduce create_rt_workqueue

create_rt_workqueue will create a real time prioritized workqueue.
This is needed for the conversion of stop_machine to a workqueue based
implementation.
This patch adds yet another parameter to __create_workqueue_key to tell
it that we want an rt workqueue.
However it looks like we rather should have something like "int type"
instead of singlethread, freezable and rt.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
---
 include/linux/workqueue.h | 18 ++++++++++--------
 kernel/workqueue.c        |  7 ++++++-
 2 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 5c158c477ac7..89a5a1231ffb 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -149,11 +149,11 @@ struct execute_work {
 
 extern struct workqueue_struct *
 __create_workqueue_key(const char *name, int singlethread,
-		       int freezeable, struct lock_class_key *key,
+		       int freezeable, int rt, struct lock_class_key *key,
 		       const char *lock_name);
 
 #ifdef CONFIG_LOCKDEP
-#define __create_workqueue(name, singlethread, freezeable)	\
+#define __create_workqueue(name, singlethread, freezeable, rt)	\
 ({								\
 	static struct lock_class_key __key;			\
 	const char *__lock_name;				\
@@ -164,17 +164,19 @@ __create_workqueue_key(const char *name, int singlethread,
 		__lock_name = #name;				\
 								\
 	__create_workqueue_key((name), (singlethread),		\
-			       (freezeable), &__key,		\
+			       (freezeable), (rt), &__key,	\
 			       __lock_name);			\
 })
 #else
-#define __create_workqueue(name, singlethread, freezeable)	\
-	__create_workqueue_key((name), (singlethread), (freezeable), NULL, NULL)
+#define __create_workqueue(name, singlethread, freezeable, rt)	\
+	__create_workqueue_key((name), (singlethread), (freezeable), (rt), \
+			       NULL, NULL)
 #endif
 
-#define create_workqueue(name) __create_workqueue((name), 0, 0)
-#define create_freezeable_workqueue(name) __create_workqueue((name), 1, 1)
-#define create_singlethread_workqueue(name) __create_workqueue((name), 1, 0)
+#define create_workqueue(name) __create_workqueue((name), 0, 0, 0)
+#define create_rt_workqueue(name) __create_workqueue((name), 0, 0, 1)
+#define create_freezeable_workqueue(name) __create_workqueue((name), 1, 1, 0)
+#define create_singlethread_workqueue(name) __create_workqueue((name), 1, 0, 0)
 
 extern void destroy_workqueue(struct workqueue_struct *wq);
 
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 714afad46539..f928f2a87b9b 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -62,6 +62,7 @@ struct workqueue_struct {
 	const char *name;
 	int singlethread;
 	int freezeable;		/* Freeze threads during suspend */
+	int rt;
 #ifdef CONFIG_LOCKDEP
 	struct lockdep_map lockdep_map;
 #endif
@@ -766,6 +767,7 @@ init_cpu_workqueue(struct workqueue_struct *wq, int cpu)
 
 static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
 {
+	struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
 	struct workqueue_struct *wq = cwq->wq;
 	const char *fmt = is_single_threaded(wq) ? "%s" : "%s/%d";
 	struct task_struct *p;
@@ -781,7 +783,8 @@ static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
 	 */
 	if (IS_ERR(p))
 		return PTR_ERR(p);
-
+	if (cwq->wq->rt)
+		sched_setscheduler_nocheck(p, SCHED_FIFO, &param);
 	cwq->thread = p;
 
 	return 0;
@@ -801,6 +804,7 @@ static void start_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
 struct workqueue_struct *__create_workqueue_key(const char *name,
 						int singlethread,
 						int freezeable,
+						int rt,
 						struct lock_class_key *key,
 						const char *lock_name)
 {
@@ -822,6 +826,7 @@ struct workqueue_struct *__create_workqueue_key(const char *name,
 	lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
 	wq->singlethread = singlethread;
 	wq->freezeable = freezeable;
+	wq->rt = rt;
 	INIT_LIST_HEAD(&wq->list);
 
 	if (singlethread) {

From c9583e55fa2b08a230c549bd1e3c0bde6c50d9cc Mon Sep 17 00:00:00 2001
From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Mon, 13 Oct 2008 23:50:10 +0200
Subject: [PATCH 10/11] stop_machine: use workqueues instead of kernel threads

Convert stop_machine to a workqueue based approach. Instead of using kernel
threads for stop_machine we now use a an rt workqueue to synchronize all
cpus.
This has the advantage that all needed per cpu threads are already created
when stop_machine gets called. And therefore a call to stop_machine won't
fail anymore. This is needed for s390 which needs a mechanism to synchronize
all cpus without allocating any memory.
As Rusty pointed out free_module() needs a non-failing stop_machine interface
as well.

As a side effect the stop_machine code gets simplified.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 kernel/stop_machine.c | 109 ++++++++++++++++--------------------------
 1 file changed, 40 insertions(+), 69 deletions(-)

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index af3c7cea258b..0e688c6a1a63 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -37,9 +37,13 @@ struct stop_machine_data {
 /* Like num_online_cpus(), but hotplug cpu uses us, so we need this. */
 static unsigned int num_threads;
 static atomic_t thread_ack;
-static struct completion finished;
 static DEFINE_MUTEX(lock);
 
+static struct workqueue_struct *stop_machine_wq;
+static struct stop_machine_data active, idle;
+static const cpumask_t *active_cpus;
+static void *stop_machine_work;
+
 static void set_state(enum stopmachine_state newstate)
 {
 	/* Reset ack counter. */
@@ -51,21 +55,25 @@ static void set_state(enum stopmachine_state newstate)
 /* Last one to ack a state moves to the next state. */
 static void ack_state(void)
 {
-	if (atomic_dec_and_test(&thread_ack)) {
-		/* If we're the last one to ack the EXIT, we're finished. */
-		if (state == STOPMACHINE_EXIT)
-			complete(&finished);
-		else
-			set_state(state + 1);
-	}
+	if (atomic_dec_and_test(&thread_ack))
+		set_state(state + 1);
 }
 
-/* This is the actual thread which stops the CPU.  It exits by itself rather
- * than waiting for kthread_stop(), because it's easier for hotplug CPU. */
-static int stop_cpu(struct stop_machine_data *smdata)
+/* This is the actual function which stops the CPU. It runs
+ * in the context of a dedicated stopmachine workqueue. */
+static void stop_cpu(struct work_struct *unused)
 {
 	enum stopmachine_state curstate = STOPMACHINE_NONE;
+	struct stop_machine_data *smdata = &idle;
+	int cpu = smp_processor_id();
 
+	if (!active_cpus) {
+		if (cpu == first_cpu(cpu_online_map))
+			smdata = &active;
+	} else {
+		if (cpu_isset(cpu, *active_cpus))
+			smdata = &active;
+	}
 	/* Simple state machine */
 	do {
 		/* Chill out and ensure we re-read stopmachine_state. */
@@ -90,7 +98,6 @@ static int stop_cpu(struct stop_machine_data *smdata)
 	} while (curstate != STOPMACHINE_EXIT);
 
 	local_irq_enable();
-	do_exit(0);
 }
 
 /* Callback for CPUs which aren't supposed to do anything. */
@@ -101,78 +108,34 @@ static int chill(void *unused)
 
 int __stop_machine(int (*fn)(void *), void *data, const cpumask_t *cpus)
 {
-	int i, err;
-	struct stop_machine_data active, idle;
-	struct task_struct **threads;
+	struct work_struct *sm_work;
+	int i;
 
+	/* Set up initial state. */
+	mutex_lock(&lock);
+	num_threads = num_online_cpus();
+	active_cpus = cpus;
 	active.fn = fn;
 	active.data = data;
 	active.fnret = 0;
 	idle.fn = chill;
 	idle.data = NULL;
 
-	/* This could be too big for stack on large machines. */
-	threads = kcalloc(NR_CPUS, sizeof(threads[0]), GFP_KERNEL);
-	if (!threads)
-		return -ENOMEM;
-
-	/* Set up initial state. */
-	mutex_lock(&lock);
-	init_completion(&finished);
-	num_threads = num_online_cpus();
 	set_state(STOPMACHINE_PREPARE);
 
-	for_each_online_cpu(i) {
-		struct stop_machine_data *smdata = &idle;
-		struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
-
-		if (!cpus) {
-			if (i == first_cpu(cpu_online_map))
-				smdata = &active;
-		} else {
-			if (cpu_isset(i, *cpus))
-				smdata = &active;
-		}
-
-		threads[i] = kthread_create((void *)stop_cpu, smdata, "kstop%u",
-					    i);
-		if (IS_ERR(threads[i])) {
-			err = PTR_ERR(threads[i]);
-			threads[i] = NULL;
-			goto kill_threads;
-		}
-
-		/* Place it onto correct cpu. */
-		kthread_bind(threads[i], i);
-
-		/* Make it highest prio. */
-		if (sched_setscheduler_nocheck(threads[i], SCHED_FIFO, &param))
-			BUG();
-	}
-
-	/* We've created all the threads.  Wake them all: hold this CPU so one
+	/* Schedule the stop_cpu work on all cpus: hold this CPU so one
 	 * doesn't hit this CPU until we're ready. */
 	get_cpu();
-	for_each_online_cpu(i)
-		wake_up_process(threads[i]);
-
+	for_each_online_cpu(i) {
+		sm_work = percpu_ptr(stop_machine_work, i);
+		INIT_WORK(sm_work, stop_cpu);
+		queue_work_on(i, stop_machine_wq, sm_work);
+	}
 	/* This will release the thread on our CPU. */
 	put_cpu();
-	wait_for_completion(&finished);
+	flush_workqueue(stop_machine_wq);
 	mutex_unlock(&lock);
-
-	kfree(threads);
-
 	return active.fnret;
-
-kill_threads:
-	for_each_online_cpu(i)
-		if (threads[i])
-			kthread_stop(threads[i]);
-	mutex_unlock(&lock);
-
-	kfree(threads);
-	return err;
 }
 
 int stop_machine(int (*fn)(void *), void *data, const cpumask_t *cpus)
@@ -187,3 +150,11 @@ int stop_machine(int (*fn)(void *), void *data, const cpumask_t *cpus)
 	return ret;
 }
 EXPORT_SYMBOL_GPL(stop_machine);
+
+static int __init stop_machine_init(void)
+{
+	stop_machine_wq = create_rt_workqueue("kstop");
+	stop_machine_work = alloc_percpu(struct work_struct);
+	return 0;
+}
+early_initcall(stop_machine_init);

From 8163bcac779f62c6bf847caed9bce905db0693fb Mon Sep 17 00:00:00 2001
From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Wed, 22 Oct 2008 10:00:26 -0500
Subject: [PATCH 11/11] stop_machine: fix error code handling on multiple cpus

Using |= for updating a value which might be updated on several cpus
concurrently will not always work since we need to make sure that the
update happens atomically.
To fix this just use a write if the called function returns an error
code on a cpu. We end up writing the error code of an arbitrary cpu
if multiple ones fail but that should be sufficient.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 kernel/stop_machine.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 0e688c6a1a63..8aff79d90ddc 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -66,6 +66,7 @@ static void stop_cpu(struct work_struct *unused)
 	enum stopmachine_state curstate = STOPMACHINE_NONE;
 	struct stop_machine_data *smdata = &idle;
 	int cpu = smp_processor_id();
+	int err;
 
 	if (!active_cpus) {
 		if (cpu == first_cpu(cpu_online_map))
@@ -86,9 +87,11 @@ static void stop_cpu(struct work_struct *unused)
 				hard_irq_disable();
 				break;
 			case STOPMACHINE_RUN:
-				/* |= allows error detection if functions on
-				 * multiple CPUs. */
-				smdata->fnret |= smdata->fn(smdata->data);
+				/* On multiple CPUs only a single error code
+				 * is needed to tell that something failed. */
+				err = smdata->fn(smdata->data);
+				if (err)
+					smdata->fnret = err;
 				break;
 			default:
 				break;