linux-kernel - Re: [PATCH] [PATCH/RESEND] driver core: remove polling for driver_probe

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Date:	Sat, 21 Feb 2009 09:28:34 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	kay.sievers@...y.org, greg@...ah.com, cornelia.huck@...ibm.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [PATCH/RESEND] driver core: remove polling for 
	driver_probe_done(v4)

2009/2/20 Arjan van de Ven <arjan@...radead.org>:
> On Fri, 20 Feb 2009 22:17:27 +0800
> tom.leiming@...il.com wrote:
>
>> From: Ming Lei <tom.leiming@...il.com>
>>
>> This patch adds a function : driver_wait_probe_done,
>> which waits on condition of probing done to replace
>> polling for driver_probe_done in fs initialization.
>>
>> There is no better way to avoid polling for
>> driver_probe_done _and_ existence of the root device,
>> so we does not replace the driver_probe_done with
>> driver_wait_probe_done in such special case.
>>
>> Removing polling in fs initialization may lead to
>> a faster boot.
>>
>> This patch is against the latest linux-next tree.
>
> you broke it i this revision though
>
>> -int wait_for_device_probe(void)
>> +void driver_wait_probe_done(void)
>>  {
>> -     /* wait for the known devices to complete their probing */
>> -     while (driver_probe_done() != 0)
>> -             msleep(100);
>> -     async_synchronize_full();
>> -     return 0;
>> +     pr_debug("%s: probe_count = %d\n", __func__,
>> +              atomic_read(&probe_count));
>> +     wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
>
>
> You lost the async_synchronize_full()!

I patch  patch-v2.6.29-rc5-next-20090220.gz against v2.6.29-rc5
directly to build
the linux-next tree(it is quicker for me),so I don't know why you add
async_synchronize_full()
 in driver core and  seems it doesn't matter with driver core.

Would you mind  that I resend a patch,which does
async_synchronize_full()  after
driver_wait_probe_done() in do_mounts.c or do_mounts_md.c ?

>
>
>> -     wait_for_device_probe();
>> +     driver_wait_probe_done();
>
> I also don't understand why you rename the function..
> wait_for_device_probe() is not a bad name ;)
> Sounds like a gratuitous change to me.

OK, I will use wait_for_device_probe().

>
>
> --
> Arjan van de Ven        Intel Open Source Technology Centre
> For development, discussion and tips for power savings,
> visit http://www.lesswatts.org
>



-- 
Lei Ming
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