linux-kernel - Re: [PATCH] kernel:async function call:introduce async

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Message-ID: <20090513153101.3bceb04c@gondolin>
Date:	Wed, 13 May 2009 15:31:01 +0200
From:	Cornelia Huck <cornelia.huck@...ibm.com>
To:	Ming Lei <tom.leiming@...il.com>
Cc:	arjan@...radead.org, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org
Subject: Re: [PATCH] kernel:async function call:introduce async_run

On Wed, 13 May 2009 20:56:40 +0800,
Ming Lei <tom.leiming@...il.com> wrote:

> 2009/5/13 Cornelia Huck <cornelia.huck@...ibm.com>:
> > On Wed, 13 May 2009 08:33:49 +0800,
> > tom.leiming@...il.com wrote:

> >>  /**
> >> + * async_run - schedule a function for asynchronous execution
> >> + * @ptr: function to execute asynchronously
> >> + * @data: data pointer to pass to the function
> >> + *
> >> + * Note:we do not allocate a cookie for this kind of aysnchronous
> >> + * function to decrease the wait time of async_synchronize_full().
> >
> > But async_synchronize_full() still waits for list_empty(&async_running)
> > - so what does this buy us?
> 
> I mean it can decrease the wait time for other async function.
> async_schedule() still can be used to do such thing, but may lead to a
> slower boot.  It is the main
> purpose of the patch.

I see how this can affect places calling async_synchronize_cookie(),
but the function will still end up on async_running. If you don't want
async_synchronize_full() waiting for these functions, couldn't you use
your own running list?

(Oh, and I just thought about it a bit further:
- somebody calls async_run() -> function with cookie = MAX_COOKIE will be
  lowest_in_progress at some point in time
- somebody else calls async_schedule() -> cookie = n
- we wait with async_synchronize_cookie(n) - which returns since
  MAX_COOKIE >= n, which is probably not what we want)
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