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

2 files changed, 67 insertions, 95 deletions

diff --git a/kernel/async.c b/kernel/async.c
index 6c68fc3fae7b..8ddee2c3e5b0 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 0023a87e8de6..56dd34976d7b 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);