From a4683487f90bfe3049686fc5c566bdc1ad03ace6 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Mon, 9 Jul 2012 19:33:30 -0700 Subject: [SCSI] async: make async_synchronize_full() flush all work regardless of domain In response to an async related regression James noted: "My theory is that this is an init problem: The assumption in a lot of our code is that async_synchronize_full() waits for everything ... even the domain specific async schedules, which isn't true." ...so make this assumption true. Each domain, including the default one, registers itself on a global domain list when work is scheduled. Once all entries complete it exits that list. Waiting for the list to be empty syncs all in-flight work across all domains. Domains can opt-out of global syncing if they are declared as exclusive ASYNC_DOMAIN_EXCLUSIVE(). All stack-based domains have been declared exclusive since the domain may go out of scope as soon as the last work item completes. Statically declared domains are mostly ok, but async_unregister_domain() is there to close any theoretical races with pending async_synchronize_full waiters at module removal time. Signed-off-by: Dan Williams Acked-by: Arjan van de Ven Reported-by: Meelis Roos Reported-by: Eldad Zack Tested-by: Eldad Zack Signed-off-by: James Bottomley --- kernel/async.c | 43 +++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 41 insertions(+), 2 deletions(-) (limited to 'kernel/async.c') diff --git a/kernel/async.c b/kernel/async.c index ba5491dfa991..9d3118384858 100644 --- a/kernel/async.c +++ b/kernel/async.c @@ -63,7 +63,9 @@ static async_cookie_t next_cookie = 1; static LIST_HEAD(async_pending); static ASYNC_DOMAIN(async_running); +static LIST_HEAD(async_domains); static DEFINE_SPINLOCK(async_lock); +static DEFINE_MUTEX(async_register_mutex); struct async_entry { struct list_head list; @@ -145,6 +147,8 @@ static void async_run_entry_fn(struct work_struct *work) /* 3) remove self from the running queue */ spin_lock_irqsave(&async_lock, flags); list_del(&entry->list); + if (running->registered && --running->count == 0) + list_del_init(&running->node); /* 4) free the entry */ kfree(entry); @@ -187,6 +191,8 @@ 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 (running->registered && running->count++ == 0) + list_add_tail(&running->node, &async_domains); atomic_inc(&entry_count); spin_unlock_irqrestore(&async_lock, flags); @@ -236,12 +242,42 @@ EXPORT_SYMBOL_GPL(async_schedule_domain); */ void async_synchronize_full(void) { + mutex_lock(&async_register_mutex); do { - async_synchronize_cookie(next_cookie); - } while (!list_empty(&async_running.domain) || !list_empty(&async_pending)); + 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); } EXPORT_SYMBOL_GPL(async_synchronize_full); +/** + * async_unregister_domain - ensure no more anonymous waiters on this domain + * @domain: idle domain to flush out of any async_synchronize_full instances + * + * async_synchronize_{cookie|full}_domain() are not flushed since callers + * of these routines should know the lifetime of @domain + * + * Prefer ASYNC_DOMAIN_EXCLUSIVE() declarations over flushing + */ +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)); + 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 @@ -268,6 +304,9 @@ void async_synchronize_cookie_domain(async_cookie_t cookie, struct async_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(); -- cgit v1.2.3