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Merge branch 'for-3.9-async' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq

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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
This commit is contained in:
Linus Torvalds
2013-02-19 22:10:26 -08:00
parent 67cb104b4c a0327ff0ed
commit ece8e0b2f9
9 changed files with 132 additions and 111 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/async.c
+60 -97
View File
@@ -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)
{
async_cookie_t first_running = next_cookie; /* infinity value */
async_cookie_t first_pending = next_cookie; /* ditto */
struct async_entry *entry;
/*
* 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;
}
list_for_each_entry(entry, &async_pending, list) {
if (entry->running == running) {
first_pending = entry->cookie;
break;
}
}
return min(first_running, first_pending);
}
static async_cookie_t lowest_in_progress(struct async_domain *running)
static async_cookie_t lowest_in_progress(struct async_domain *domain)
{
struct async_entry *first = NULL;
async_cookie_t ret = ASYNC_COOKIE_MAX;
unsigned long flags;
async_cookie_t ret;
spin_lock_irqsave(&async_lock, flags);
ret = __lowest_in_progress(running);
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);
}
if (first)
ret = first->cookie;
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);
kernel/kmod.c
+9
View File
@@ -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);