From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761009AbZEMRL7 (ORCPT ); Wed, 13 May 2009 13:11:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759645AbZEMRLs (ORCPT ); Wed, 13 May 2009 13:11:48 -0400 Received: from mtagate3.de.ibm.com ([195.212.29.152]:65325 "EHLO mtagate3.de.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757919AbZEMRLs (ORCPT ); Wed, 13 May 2009 13:11:48 -0400 Date: Wed, 13 May 2009 19:11:44 +0200 From: Cornelia Huck To: tom.leiming@gmail.com Cc: arjan@infradead.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Ming Lei Subject: Re: [PATCH] kernel:async function call:introduce async_run_inatomic(v2) Message-ID: <20090513191144.6aae00d7@gondolin> In-Reply-To: <1242229899-16761-1-git-send-email-tom.leiming@gmail.com> References: <1242229899-16761-1-git-send-email-tom.leiming@gmail.com> Organization: IBM Deutschland Research & Development GmbH Vorsitzender des Aufsichtsrats: Martin Jetter =?ISO-8859-15?Q?Gesch=E4ftsf=FChrung:?= Erich Baier Sitz der Gesellschaft: =?ISO-8859-15?Q?B=F6blingen?= Registergericht: Amtsgericht Stuttgart, HRB 243294 X-Mailer: Claws Mail 3.7.1 (GTK+ 2.16.1; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 13 May 2009 23:51:39 +0800, tom.leiming@gmail.com wrote: > From: Ming Lei > > The purpose of this function is to offer a simple way to schedule an > asynchronous thread from an atomic context, because there are not any > functions which can create and start a kernel thread in atomic contexts > now. We use async_running_no_sync as running list to make callers that > don't want to synchronize on cookies, so can avoid some side effects for > async_synchronize_full(). > > Part of note for async_run_inatomic and some guideline is from Cornelia Huck. > > Signed-off-by: Ming Lei > Signed-off-by: Cornelia Huck > --- > include/linux/async.h | 2 ++ > kernel/async.c | 23 +++++++++++++++++++++++ > 2 files changed, 25 insertions(+), 0 deletions(-) > > diff --git a/include/linux/async.h b/include/linux/async.h > index 18ce92b..9ff62af 100644 > --- a/include/linux/async.h > +++ b/include/linux/async.h > @@ -16,6 +16,8 @@ > typedef u64 async_cookie_t; > typedef void (async_func_ptr) (void *data, async_cookie_t cookie); > > +extern int async_run_inatomic(async_func_ptr *ptr, void *data); > + > 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 list_head *list); > diff --git a/kernel/async.c b/kernel/async.c > index 8663f5b..cb527b3 100644 > --- a/kernel/async.c > +++ b/kernel/async.c > @@ -65,6 +65,7 @@ static async_cookie_t next_cookie = 1; > > static LIST_HEAD(async_pending); > static LIST_HEAD(async_running); > +static LIST_HEAD(async_running_no_sync); > static DEFINE_SPINLOCK(async_lock); > > static int async_enabled = 0; > @@ -222,6 +223,28 @@ static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, > return newcookie; > } > > + /** > + * async_run_inatomic - in atomic contexts schedule a function for > + * asynchronous execution I'm not 100% sure whether kerneldoc likes split lines for the description. "async_run_inatomic - schedule a function for asynchronous execution from atomic context without checkpointing" - but that's really a bit long... > + * > + * @ptr: function to execute asynchronously > + * @data: data pointer to pass to the function > + * > + * Return zero if success, or else return others if failured Returns zero on success, !zero on failure > + * Note: I'd move the description of the function's purpose before Note:. > + * The purpose of this function is to offer a simple way to schedule an > + * asynchronous thread from an atomic context, because there are not any > + * functions which can create and start a kernel thread in atomic contexts > + * now. I don't think the second part of the sentence is needed, this should only be mentioned in the patch description. I'd rather add "Since it does not return a cookie for checkpointing, it is for callers that don't need later synchronization." > We use async_running_no_sync as running list to make callers that > + * don't want to synchronize on cookies, so can avoid some side effects for > + * async_synchronize_full(). "async_run_inatomic() uses a distinct running list in order to avoid slowing down synchronization within the general domain." (The cookie will still be checked when __lowest_in_progress() returns the cookie for the async_pending list, but I think that is negligible - and it would be a general issue for special domains.) > + */ > +int async_run_inatomic(async_func_ptr *ptr, void *data) > +{ > + return !__async_schedule(ptr, data, &async_running_no_sync, 1); > +} > +EXPORT_SYMBOL_GPL(async_run_inatomic); > + > /** > * async_schedule - schedule a function for asynchronous execution > * @ptr: function to execute asynchronously Btw: Do you have any specific use cases for this function in mind?