Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757364Ab2E3SGS (ORCPT ); Wed, 30 May 2012 14:06:18 -0400 Received: from mga01.intel.com ([192.55.52.88]:47691 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757279Ab2E3SFN (ORCPT ); Wed, 30 May 2012 14:05:13 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.71,315,1320652800"; d="scan'208";a="172880603" Subject: [PATCH v2 2/4] async: make async_synchronize_full() flush all work regardless of domain To: linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org From: Dan Williams Cc: Len Brown , Meelis Roos , James Bottomley , Eldad Zack , "Rafael J. Wysocki" , Arjan van de Ven Date: Wed, 30 May 2012 11:21:35 -0700 Message-ID: <20120530182135.23574.9220.stgit@dwillia2-linux.jf.intel.com> In-Reply-To: <20120530182016.23574.11056.stgit@dwillia2-linux.jf.intel.com> References: <20120530182016.23574.11056.stgit@dwillia2-linux.jf.intel.com> User-Agent: StGit/0.16-1-g7004 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5700 Lines: 153 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. Cc: Arjan van de Ven Cc: Len Brown Cc: Rafael J. Wysocki Cc: James Bottomley Reported-by: Meelis Roos Reported-by: Eldad Zack Signed-off-by: Dan Williams --- drivers/scsi/scsi.c | 1 + include/linux/async.h | 1 + kernel/async.c | 43 +++++++++++++++++++++++++++++++++++++++++-- 3 files changed, 43 insertions(+), 2 deletions(-) diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c index 2f92007..2dd3c93 100644 --- a/drivers/scsi/scsi.c +++ b/drivers/scsi/scsi.c @@ -1355,6 +1355,7 @@ static void __exit exit_scsi(void) scsi_exit_devinfo(); scsi_exit_procfs(); scsi_exit_queue(); + async_unregister_domain(&scsi_sd_probe_domain); } subsys_initcall(init_scsi); diff --git a/include/linux/async.h b/include/linux/async.h index 364e7ff..7a24fe9 100644 --- a/include/linux/async.h +++ b/include/linux/async.h @@ -46,6 +46,7 @@ struct async_domain { extern async_cookie_t async_schedule(async_func_ptr *ptr, void *data); extern async_cookie_t async_schedule_domain(async_func_ptr *ptr, void *data, struct async_domain *domain); +void async_unregister_domain(struct async_domain *domain); extern void async_synchronize_full(void); extern void async_synchronize_full_domain(struct async_domain *domain); extern void async_synchronize_cookie(async_cookie_t cookie); diff --git a/kernel/async.c b/kernel/async.c index ba5491d..9d31183 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); @@ -236,13 +242,43 @@ 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(); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/