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authorLinus Torvalds <torvalds@linux-foundation.org>2013-02-19 22:10:26 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2013-02-19 22:10:26 -0800
commitece8e0b2f9c980e5511fe8db2d68c6f1859b9d83 (patch)
tree70f1e3363080884965686576d079d24da8863a58
parent67cb104b4c30bd52292b6a7f526349aab2dd5cbd (diff)
parenta0327ff0eda915be623658babacef706099c11a8 (diff)
downloadvexpress-lsk-ece8e0b2f9c980e5511fe8db2d68c6f1859b9d83.tar.gz
Merge branch 'for-3.9-async' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq
Pull async changes from Tejun Heo: "These are followups for the earlier deadlock issue involving async ending up waiting for itself through block requesting module[1]. The following changes are made by these commits. - Instead of requesting default elevator on each request_queue init, block now requests it once early during boot. - Kmod triggers warning if invoked from an async worker. - Async synchronization implementation has been reimplemented. It's a lot simpler now." * 'for-3.9-async' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq: async: initialise list heads to fix crash async: replace list of active domains with global list of pending items async: keep pending tasks on async_domain and remove async_pending async: use ULLONG_MAX for infinity cookie value async: bring sanity to the use of words domain and running async, kmod: warn on synchronous request_module() from async workers block: don't request module during elevator init init, block: try to load default elevator module early during boot
-rw-r--r--block/elevator.c35
-rw-r--r--include/linux/async.h9
-rw-r--r--include/linux/elevator.h5
-rw-r--r--include/linux/init.h1
-rw-r--r--init/do_mounts_initrd.c3
-rw-r--r--init/initramfs.c8
-rw-r--r--init/main.c16
-rw-r--r--kernel/async.c153
-rw-r--r--kernel/kmod.c9
9 files changed, 130 insertions, 109 deletions
diff --git a/block/elevator.c b/block/elevator.c
index 9edba1b8323..603b2c17874 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -100,14 +100,14 @@ static void elevator_put(struct elevator_type *e)
module_put(e->elevator_owner);
}
-static struct elevator_type *elevator_get(const char *name)
+static struct elevator_type *elevator_get(const char *name, bool try_loading)
{
struct elevator_type *e;
spin_lock(&elv_list_lock);
e = elevator_find(name);
- if (!e) {
+ if (!e && try_loading) {
spin_unlock(&elv_list_lock);
request_module("%s-iosched", name);
spin_lock(&elv_list_lock);
@@ -136,6 +136,22 @@ static int __init elevator_setup(char *str)
__setup("elevator=", elevator_setup);
+/* called during boot to load the elevator chosen by the elevator param */
+void __init load_default_elevator_module(void)
+{
+ struct elevator_type *e;
+
+ if (!chosen_elevator[0])
+ return;
+
+ spin_lock(&elv_list_lock);
+ e = elevator_find(chosen_elevator);
+ spin_unlock(&elv_list_lock);
+
+ if (!e)
+ request_module("%s-iosched", chosen_elevator);
+}
+
static struct kobj_type elv_ktype;
static struct elevator_queue *elevator_alloc(struct request_queue *q,
@@ -191,25 +207,30 @@ int elevator_init(struct request_queue *q, char *name)
q->boundary_rq = NULL;
if (name) {
- e = elevator_get(name);
+ e = elevator_get(name, true);
if (!e)
return -EINVAL;
}
+ /*
+ * Use the default elevator specified by config boot param or
+ * config option. Don't try to load modules as we could be running
+ * off async and request_module() isn't allowed from async.
+ */
if (!e && *chosen_elevator) {
- e = elevator_get(chosen_elevator);
+ e = elevator_get(chosen_elevator, false);
if (!e)
printk(KERN_ERR "I/O scheduler %s not found\n",
chosen_elevator);
}
if (!e) {
- e = elevator_get(CONFIG_DEFAULT_IOSCHED);
+ e = elevator_get(CONFIG_DEFAULT_IOSCHED, false);
if (!e) {
printk(KERN_ERR
"Default I/O scheduler not found. " \
"Using noop.\n");
- e = elevator_get("noop");
+ e = elevator_get("noop", false);
}
}
@@ -951,7 +972,7 @@ int elevator_change(struct request_queue *q, const char *name)
return -ENXIO;
strlcpy(elevator_name, name, sizeof(elevator_name));
- e = elevator_get(strstrip(elevator_name));
+ e = elevator_get(strstrip(elevator_name), true);
if (!e) {
printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
return -EINVAL;
diff --git a/include/linux/async.h b/include/linux/async.h
index 345169cfa30..a2e3f18b2ad 100644
--- a/include/linux/async.h
+++ b/include/linux/async.h
@@ -19,8 +19,7 @@ typedef u64 async_cookie_t;
typedef void (async_func_ptr) (void *data, async_cookie_t cookie);
struct async_domain {
struct list_head node;
- struct list_head domain;
- int count;
+ struct list_head pending;
unsigned registered:1;
};
@@ -29,8 +28,7 @@ struct async_domain {
*/
#define ASYNC_DOMAIN(_name) \
struct async_domain _name = { .node = LIST_HEAD_INIT(_name.node), \
- .domain = LIST_HEAD_INIT(_name.domain), \
- .count = 0, \
+ .pending = LIST_HEAD_INIT(_name.pending), \
.registered = 1 }
/*
@@ -39,8 +37,7 @@ struct async_domain {
*/
#define ASYNC_DOMAIN_EXCLUSIVE(_name) \
struct async_domain _name = { .node = LIST_HEAD_INIT(_name.node), \
- .domain = LIST_HEAD_INIT(_name.domain), \
- .count = 0, \
+ .pending = LIST_HEAD_INIT(_name.pending), \
.registered = 0 }
extern async_cookie_t async_schedule(async_func_ptr *ptr, void *data);
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index c03af7687bb..18662063175 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -138,6 +138,7 @@ extern void elv_drain_elevator(struct request_queue *);
/*
* io scheduler registration
*/
+extern void __init load_default_elevator_module(void);
extern int elv_register(struct elevator_type *);
extern void elv_unregister(struct elevator_type *);
@@ -206,5 +207,9 @@ enum {
INIT_LIST_HEAD(&(rq)->csd.list); \
} while (0)
+#else /* CONFIG_BLOCK */
+
+static inline void load_default_elevator_module(void) { }
+
#endif /* CONFIG_BLOCK */
#endif
diff --git a/include/linux/init.h b/include/linux/init.h
index 10ed4f43645..861814710d5 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -153,6 +153,7 @@ extern unsigned int reset_devices;
/* used by init/main.c */
void setup_arch(char **);
void prepare_namespace(void);
+void __init load_default_modules(void);
extern void (*late_time_init)(void);
diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c
index f9acf71b981..a32ec1ce882 100644
--- a/init/do_mounts_initrd.c
+++ b/init/do_mounts_initrd.c
@@ -61,6 +61,9 @@ static void __init handle_initrd(void)
sys_mkdir("/old", 0700);
sys_chdir("/old");
+ /* try loading default modules from initrd */
+ load_default_modules();
+
/*
* In case that a resume from disk is carried out by linuxrc or one of
* its children, we need to tell the freezer not to wait for us.
diff --git a/init/initramfs.c b/init/initramfs.c
index 84c6bf11130..a67ef9dbda9 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -592,7 +592,7 @@ static int __init populate_rootfs(void)
initrd_end - initrd_start);
if (!err) {
free_initrd();
- return 0;
+ goto done;
} else {
clean_rootfs();
unpack_to_rootfs(__initramfs_start, __initramfs_size);
@@ -607,6 +607,7 @@ static int __init populate_rootfs(void)
sys_close(fd);
free_initrd();
}
+ done:
#else
printk(KERN_INFO "Unpacking initramfs...\n");
err = unpack_to_rootfs((char *)initrd_start,
@@ -615,6 +616,11 @@ static int __init populate_rootfs(void)
printk(KERN_EMERG "Initramfs unpacking failed: %s\n", err);
free_initrd();
#endif
+ /*
+ * Try loading default modules from initramfs. This gives
+ * us a chance to load before device_initcalls.
+ */
+ load_default_modules();
}
return 0;
}
diff --git a/init/main.c b/init/main.c
index cee4b5c66d8..63534a141b4 100644
--- a/init/main.c
+++ b/init/main.c
@@ -70,6 +70,8 @@
#include <linux/perf_event.h>
#include <linux/file.h>
#include <linux/ptrace.h>
+#include <linux/blkdev.h>
+#include <linux/elevator.h>
#include <asm/io.h>
#include <asm/bugs.h>
@@ -794,6 +796,17 @@ static void __init do_pre_smp_initcalls(void)
do_one_initcall(*fn);
}
+/*
+ * This function requests modules which should be loaded by default and is
+ * called twice right after initrd is mounted and right before init is
+ * exec'd. If such modules are on either initrd or rootfs, they will be
+ * loaded before control is passed to userland.
+ */
+void __init load_default_modules(void)
+{
+ load_default_elevator_module();
+}
+
static int run_init_process(const char *init_filename)
{
argv_init[0] = init_filename;
@@ -900,4 +913,7 @@ static noinline void __init kernel_init_freeable(void)
* we're essentially up and running. Get rid of the
* initmem segments and start the user-mode stuff..
*/
+
+ /* rootfs is available now, try loading default modules */
+ load_default_modules();
}
diff --git a/kernel/async.c b/kernel/async.c
index 6c68fc3fae7..8ddee2c3e5b 100644
--- a/kernel/async.c
+++ b/kernel/async.c
@@ -61,63 +61,48 @@ asynchronous and synchronous parts of the kernel.
static async_cookie_t next_cookie = 1;
-#define MAX_WORK 32768
+#define MAX_WORK 32768
+#define ASYNC_COOKIE_MAX ULLONG_MAX /* infinity cookie */
-static LIST_HEAD(async_pending);
-static ASYNC_DOMAIN(async_running);
-static LIST_HEAD(async_domains);
+static LIST_HEAD(async_global_pending); /* pending from all registered doms */
+static ASYNC_DOMAIN(async_dfl_domain);
static DEFINE_SPINLOCK(async_lock);
-static DEFINE_MUTEX(async_register_mutex);
struct async_entry {
- struct list_head list;
+ struct list_head domain_list;
+ struct list_head global_list;
struct work_struct work;
async_cookie_t cookie;
async_func_ptr *func;
void *data;
- struct async_domain *running;
+ struct async_domain *domain;
};
static DECLARE_WAIT_QUEUE_HEAD(async_done);
static atomic_t entry_count;
-
-/*
- * MUST be called with the lock held!
- */
-static async_cookie_t __lowest_in_progress(struct async_domain *running)
+static async_cookie_t lowest_in_progress(struct async_domain *domain)
{
- async_cookie_t first_running = next_cookie; /* infinity value */
- async_cookie_t first_pending = next_cookie; /* ditto */
- struct async_entry *entry;
+ struct async_entry *first = NULL;
+ async_cookie_t ret = ASYNC_COOKIE_MAX;
+ unsigned long flags;
- /*
- * Both running and pending lists are sorted but not disjoint.
- * Take the first cookies from both and return the min.
- */
- if (!list_empty(&running->domain)) {
- entry = list_first_entry(&running->domain, typeof(*entry), list);
- first_running = entry->cookie;
- }
+ spin_lock_irqsave(&async_lock, flags);
- list_for_each_entry(entry, &async_pending, list) {
- if (entry->running == running) {
- first_pending = entry->cookie;
- break;
- }
+ if (domain) {
+ if (!list_empty(&domain->pending))
+ first = list_first_entry(&domain->pending,
+ struct async_entry, domain_list);
+ } else {
+ if (!list_empty(&async_global_pending))
+ first = list_first_entry(&async_global_pending,
+ struct async_entry, global_list);
}
- return min(first_running, first_pending);
-}
+ if (first)
+ ret = first->cookie;
-static async_cookie_t lowest_in_progress(struct async_domain *running)
-{
- unsigned long flags;
- async_cookie_t ret;
-
- spin_lock_irqsave(&async_lock, flags);
- ret = __lowest_in_progress(running);
spin_unlock_irqrestore(&async_lock, flags);
return ret;
}
@@ -129,20 +114,10 @@ static void async_run_entry_fn(struct work_struct *work)
{
struct async_entry *entry =
container_of(work, struct async_entry, work);
- struct async_entry *pos;
unsigned long flags;
ktime_t uninitialized_var(calltime), delta, rettime;
- struct async_domain *running = entry->running;
-
- /* 1) move self to the running queue, make sure it stays sorted */
- spin_lock_irqsave(&async_lock, flags);
- list_for_each_entry_reverse(pos, &running->domain, list)
- if (entry->cookie < pos->cookie)
- break;
- list_move_tail(&entry->list, &pos->list);
- spin_unlock_irqrestore(&async_lock, flags);
- /* 2) run (and print duration) */
+ /* 1) run (and print duration) */
if (initcall_debug && system_state == SYSTEM_BOOTING) {
printk(KERN_DEBUG "calling %lli_%pF @ %i\n",
(long long)entry->cookie,
@@ -159,23 +134,22 @@ static void async_run_entry_fn(struct work_struct *work)
(long long)ktime_to_ns(delta) >> 10);
}
- /* 3) remove self from the running queue */
+ /* 2) remove self from the pending queues */
spin_lock_irqsave(&async_lock, flags);
- list_del(&entry->list);
- if (running->registered && --running->count == 0)
- list_del_init(&running->node);
+ list_del_init(&entry->domain_list);
+ list_del_init(&entry->global_list);
- /* 4) free the entry */
+ /* 3) free the entry */
kfree(entry);
atomic_dec(&entry_count);
spin_unlock_irqrestore(&async_lock, flags);
- /* 5) wake up any waiters */
+ /* 4) wake up any waiters */
wake_up(&async_done);
}
-static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct async_domain *running)
+static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct async_domain *domain)
{
struct async_entry *entry;
unsigned long flags;
@@ -198,16 +172,22 @@ static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct a
ptr(data, newcookie);
return newcookie;
}
+ INIT_LIST_HEAD(&entry->domain_list);
+ INIT_LIST_HEAD(&entry->global_list);
INIT_WORK(&entry->work, async_run_entry_fn);
entry->func = ptr;
entry->data = data;
- entry->running = running;
+ entry->domain = domain;
spin_lock_irqsave(&async_lock, flags);
+
+ /* allocate cookie and queue */
newcookie = entry->cookie = next_cookie++;
- list_add_tail(&entry->list, &async_pending);
- if (running->registered && running->count++ == 0)
- list_add_tail(&running->node, &async_domains);
+
+ list_add_tail(&entry->domain_list, &domain->pending);
+ if (domain->registered)
+ list_add_tail(&entry->global_list, &async_global_pending);
+
atomic_inc(&entry_count);
spin_unlock_irqrestore(&async_lock, flags);
@@ -230,7 +210,7 @@ static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct a
*/
async_cookie_t async_schedule(async_func_ptr *ptr, void *data)
{
- return __async_schedule(ptr, data, &async_running);
+ return __async_schedule(ptr, data, &async_dfl_domain);
}
EXPORT_SYMBOL_GPL(async_schedule);
@@ -238,18 +218,18 @@ EXPORT_SYMBOL_GPL(async_schedule);
* async_schedule_domain - schedule a function for asynchronous execution within a certain domain
* @ptr: function to execute asynchronously
* @data: data pointer to pass to the function
- * @running: running list for the domain
+ * @domain: the domain
*
* Returns an async_cookie_t that may be used for checkpointing later.
- * @running may be used in the async_synchronize_*_domain() functions
- * to wait within a certain synchronization domain rather than globally.
- * A synchronization domain is specified via the running queue @running to use.
- * Note: This function may be called from atomic or non-atomic contexts.
+ * @domain may be used in the async_synchronize_*_domain() functions to
+ * wait within a certain synchronization domain rather than globally. A
+ * synchronization domain is specified via @domain. Note: This function
+ * may be called from atomic or non-atomic contexts.
*/
async_cookie_t async_schedule_domain(async_func_ptr *ptr, void *data,
- struct async_domain *running)
+ struct async_domain *domain)
{
- return __async_schedule(ptr, data, running);
+ return __async_schedule(ptr, data, domain);
}
EXPORT_SYMBOL_GPL(async_schedule_domain);
@@ -260,18 +240,7 @@ EXPORT_SYMBOL_GPL(async_schedule_domain);
*/
void async_synchronize_full(void)
{
- mutex_lock(&async_register_mutex);
- do {
- struct async_domain *domain = NULL;
-
- spin_lock_irq(&async_lock);
- if (!list_empty(&async_domains))
- domain = list_first_entry(&async_domains, typeof(*domain), node);
- spin_unlock_irq(&async_lock);
-
- async_synchronize_cookie_domain(next_cookie, domain);
- } while (!list_empty(&async_domains));
- mutex_unlock(&async_register_mutex);
+ async_synchronize_full_domain(NULL);
}
EXPORT_SYMBOL_GPL(async_synchronize_full);
@@ -286,51 +255,45 @@ EXPORT_SYMBOL_GPL(async_synchronize_full);
*/
void async_unregister_domain(struct async_domain *domain)
{
- mutex_lock(&async_register_mutex);
spin_lock_irq(&async_lock);
- WARN_ON(!domain->registered || !list_empty(&domain->node) ||
- !list_empty(&domain->domain));
+ WARN_ON(!domain->registered || !list_empty(&domain->pending));
domain->registered = 0;
spin_unlock_irq(&async_lock);
- mutex_unlock(&async_register_mutex);
}
EXPORT_SYMBOL_GPL(async_unregister_domain);
/**
* async_synchronize_full_domain - synchronize all asynchronous function within a certain domain
- * @domain: running list to synchronize on
+ * @domain: the domain to synchronize
*
* This function waits until all asynchronous function calls for the
- * synchronization domain specified by the running list @domain have been done.
+ * synchronization domain specified by @domain have been done.
*/
void async_synchronize_full_domain(struct async_domain *domain)
{
- async_synchronize_cookie_domain(next_cookie, domain);
+ async_synchronize_cookie_domain(ASYNC_COOKIE_MAX, domain);
}
EXPORT_SYMBOL_GPL(async_synchronize_full_domain);
/**
* async_synchronize_cookie_domain - synchronize asynchronous function calls within a certain domain with cookie checkpointing
* @cookie: async_cookie_t to use as checkpoint
- * @running: running list to synchronize on
+ * @domain: the domain to synchronize (%NULL for all registered domains)
*
* This function waits until all asynchronous function calls for the
- * synchronization domain specified by running list @running submitted
- * prior to @cookie have been done.
+ * synchronization domain specified by @domain submitted prior to @cookie
+ * have been done.
*/
-void async_synchronize_cookie_domain(async_cookie_t cookie, struct async_domain *running)
+void async_synchronize_cookie_domain(async_cookie_t cookie, struct async_domain *domain)
{
ktime_t uninitialized_var(starttime), delta, endtime;
- if (!running)
- return;
-
if (initcall_debug && system_state == SYSTEM_BOOTING) {
printk(KERN_DEBUG "async_waiting @ %i\n", task_pid_nr(current));
starttime = ktime_get();
}
- wait_event(async_done, lowest_in_progress(running) >= cookie);
+ wait_event(async_done, lowest_in_progress(domain) >= cookie);
if (initcall_debug && system_state == SYSTEM_BOOTING) {
endtime = ktime_get();
@@ -352,7 +315,7 @@ EXPORT_SYMBOL_GPL(async_synchronize_cookie_domain);
*/
void async_synchronize_cookie(async_cookie_t cookie)
{
- async_synchronize_cookie_domain(cookie, &async_running);
+ async_synchronize_cookie_domain(cookie, &async_dfl_domain);
}
EXPORT_SYMBOL_GPL(async_synchronize_cookie);
diff --git a/kernel/kmod.c b/kernel/kmod.c
index 0023a87e8de..56dd34976d7 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -38,6 +38,7 @@
#include <linux/suspend.h>
#include <linux/rwsem.h>
#include <linux/ptrace.h>
+#include <linux/async.h>
#include <asm/uaccess.h>
#include <trace/events/module.h>
@@ -130,6 +131,14 @@ int __request_module(bool wait, const char *fmt, ...)
#define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */
static int kmod_loop_msg;
+ /*
+ * We don't allow synchronous module loading from async. Module
+ * init may invoke async_synchronize_full() which will end up
+ * waiting for this task which already is waiting for the module
+ * loading to complete, leading to a deadlock.
+ */
+ WARN_ON_ONCE(wait && current_is_async());
+
va_start(args, fmt);
ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
va_end(args);