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Date: Fri, 18 Jan 2013 16:40:38 -0800
From: Tejun Heo <tj@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>,
Arjan van de Ven <arjan@...ux.intel.com>,
Dan Williams <djbw@...com>
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH 3/4] async: keep pending tasks on async_domain and remove
async_pending
>From e5877615929e13719fde210bc4b776bfd25c16c8 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@...nel.org>
Date: Fri, 18 Jan 2013 16:34:16 -0800
Async kept single global pending list and per-domain running lists.
When an async item is queued, it's put on the global pending list.
The item is moved to the per-domain running list when its execution
starts.
At this point, this design complicates execution and synchronization
without bringing any benefit. The list only matters for
synchronization which doesn't care whether a given async item is
pending or executing. Also, global synchronization is done by
iterating through all active registered async_domains, so the global
async_pending list doesn't help anything either.
Rename async_domain->running to async_domain->pending and put async
items directly there and remove when execution completes. This
simplifies lowest_in_progress() a lot - the first item on the pending
list is the one with the lowest cookie, and async_run_entry_fn()
doesn't have to mess with moving the item from pending to running.
After the change, whether a domain is empty or not can be trivially
determined by looking at async_domain->pending. Remove
async_domain->count and use list_empty() on pending instead.
Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: Arjan van de Ven <arjan@...ux.intel.com>
Cc: Dan Williams <djbw@...com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
---
include/linux/async.h | 9 +++-----
kernel/async.c | 63 ++++++++++++---------------------------------------
2 files changed, 17 insertions(+), 55 deletions(-)
diff --git a/include/linux/async.h b/include/linux/async.h
index 6f23442..849fb8c 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 running;
- 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), \
- .running = LIST_HEAD_INIT(_name.running), \
- .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), \
- .running = LIST_HEAD_INIT(_name.running), \
- .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/kernel/async.c b/kernel/async.c
index 4cb4823..711fc34 100644
--- a/kernel/async.c
+++ b/kernel/async.c
@@ -62,7 +62,6 @@ static async_cookie_t next_cookie = 1;
#define MAX_WORK 32768
#define ASYNC_COOKIE_MAX ULLONG_MAX /* infinity cookie */
-static LIST_HEAD(async_pending);
static ASYNC_DOMAIN(async_dfl_domain);
static LIST_HEAD(async_domains);
static DEFINE_SPINLOCK(async_lock);
@@ -81,42 +80,17 @@ 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 *domain)
-{
- async_cookie_t first_running = ASYNC_COOKIE_MAX;
- async_cookie_t first_pending = ASYNC_COOKIE_MAX;
- 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(&domain->running)) {
- entry = list_first_entry(&domain->running, typeof(*entry), list);
- first_running = entry->cookie;
- }
-
- list_for_each_entry(entry, &async_pending, list) {
- if (entry->domain == domain) {
- first_pending = entry->cookie;
- break;
- }
- }
-
- return min(first_running, first_pending);
-}
-
static async_cookie_t lowest_in_progress(struct async_domain *domain)
{
+ async_cookie_t ret = ASYNC_COOKIE_MAX;
unsigned long flags;
- async_cookie_t ret;
spin_lock_irqsave(&async_lock, flags);
- ret = __lowest_in_progress(domain);
+ if (!list_empty(&domain->pending)) {
+ struct async_entry *first = list_first_entry(&domain->pending,
+ struct async_entry, list);
+ ret = first->cookie;
+ }
spin_unlock_irqrestore(&async_lock, flags);
return ret;
}
@@ -128,20 +102,11 @@ 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 *domain = entry->domain;
- /* 1) move self to the running queue, make sure it stays sorted */
- spin_lock_irqsave(&async_lock, flags);
- list_for_each_entry_reverse(pos, &domain->running, 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,
@@ -158,19 +123,19 @@ 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 (domain->registered && --domain->count == 0)
+ if (domain->registered && list_empty(&domain->pending))
list_del_init(&domain->node);
- /* 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);
}
@@ -204,9 +169,9 @@ static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct a
spin_lock_irqsave(&async_lock, flags);
newcookie = entry->cookie = next_cookie++;
- list_add_tail(&entry->list, &async_pending);
- if (domain->registered && domain->count++ == 0)
+ if (domain->registered && list_empty(&domain->pending))
list_add_tail(&domain->node, &async_domains);
+ list_add_tail(&entry->list, &domain->pending);
atomic_inc(&entry_count);
spin_unlock_irqrestore(&async_lock, flags);
@@ -285,7 +250,7 @@ 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->running));
+ !list_empty(&domain->pending));
domain->registered = 0;
spin_unlock_irq(&async_lock);
mutex_unlock(&async_register_mutex);
--
1.8.0.2
--
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