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author | Linus Torvalds <torvalds@linux-foundation.org> | 2013-02-19 22:10:26 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-02-19 22:10:26 -0800 |
commit | ece8e0b2f9c980e5511fe8db2d68c6f1859b9d83 (patch) | |
tree | 70f1e3363080884965686576d079d24da8863a58 /kernel | |
parent | 67cb104b4c30bd52292b6a7f526349aab2dd5cbd (diff) | |
parent | a0327ff0eda915be623658babacef706099c11a8 (diff) | |
download | linux-ece8e0b2f9c980e5511fe8db2d68c6f1859b9d83.tar.gz linux-ece8e0b2f9c980e5511fe8db2d68c6f1859b9d83.tar.bz2 linux-ece8e0b2f9c980e5511fe8db2d68c6f1859b9d83.zip |
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.c | 153 | ||||
-rw-r--r-- | kernel/kmod.c | 9 |
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); |