linux-kernel - Re: [3.8-rc3 -> 3.8-rc4 regression] Re: [PATCH] module, async: async_synchronize

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Date:	Tue, 26 Nov 2013 16:12:41 -0600
From:	Josh Hunt <joshhunt00@...il.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Tejun Heo <tj@...nel.org>, Jonathan Nieder <jrnieder@...il.com>,
	Ming Lei <ming.lei@...onical.com>,
	Alex Riesen <raa.lkml@...il.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Jens Axboe <axboe@...nel.dk>,
	USB list <linux-usb@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [3.8-rc3 -> 3.8-rc4 regression] Re: [PATCH] module, async:
 async_synchronize_full() on module init iff async is used

On Tue, Nov 26, 2013 at 3:53 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Tue, Nov 26, 2013 at 1:29 PM, Josh Hunt <joshhunt00@...il.com> wrote:
>>
>> Both ahci and sata_svw call ata_host_activate(), which call
>> ata_host_register() and async_schedule(async_port_probe, ap).
>
> Well, with the modern logic ("only wait for async probing if the
> module itself did async probing") the ahci and svw modules didn't
> really change any behavior.
>
> But other modules did. I wonder, for example, if people insmod the dm
> module, and expect all devices to exist afterwards. Which the old
> logic of "we always wait for all async code regardless of whether we
> started it ourselves" would do, but the new logic does not.
>
> Something similar might hit the (non-modular) md auto-detect ioctl.
>
> So maybe we should just special-case those two issues, and say "let's
> just wait for async requests here"
>
> Something like the appended (whitespace-damaged) diff. Does that make
> a difference to you guys? And if it does, can you check *which* of the
> two async_synchronize_full() calls it is that matters for your cases?
>
>                  Linus
>
> --- duh, apply by hand --
>
>     diff --git a/drivers/md/dm.c b/drivers/md/dm.c
>     index 0704c523a76b..7e7a2f743b11 100644
>     --- a/drivers/md/dm.c
>     +++ b/drivers/md/dm.c
>     @@ -351,6 +351,7 @@ static int __init dm_init(void)
>                             goto bad;
>             }
>
>     +       async_synchronize_full();
>             return 0;
>
>            bad:
>     diff --git a/drivers/md/md.c b/drivers/md/md.c
>     index b6b7a2866c9e..1d173dc662fc 100644
>     --- a/drivers/md/md.c
>     +++ b/drivers/md/md.c
>     @@ -8602,6 +8602,7 @@ static void autostart_arrays(int part)
>             i_scanned = 0;
>             i_passed = 0;
>
>     +       async_synchronize_full();
>             printk(KERN_INFO "md: Autodetecting RAID arrays.\n");
>
>             while (!list_empty(&all_detected_devices) && i_scanned < INT_MAX) {

I should have clarified that I'm not using dm/md in my setup. I know
the modules are getting loaded in the log I attached, but root is not
a md/dm device.

-- 
Josh
--
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