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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 /kernel
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
Diffstat (limited to 'kernel')
-rw-r--r--kernel/async.c153
-rw-r--r--kernel/kmod.c9
2 files changed, 67 insertions, 95 deletions
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);