Re: udev queue error

[Kay Sievers <kay.sievers@xxxxxxxx>]

On Tue, May 31, 2011 at 17:31, Tejun Heo <htejun@xxxxxxxxx> wrote:
> On Mon, May 30, 2011 at 10:06:49PM +0200, Kay Sievers wrote:
>> Yeah, the fake cdrom on the stick seems pretty broken. It generates
>> media-changed events on very open(), and udev runs open() for the new
>> event, which ... creates the loop you are seeing.
>
> Ugh... :-(
>
>> We need to find a way to work around such issues in the kernel, I guess.
>>
>> Tejun, any idea?
>
> Hmmm... a couple of questions.
>
> * udev doesn't open device w/ O_EXCL, right?

Cdrom_id uses O_EXCL if the disk is not mounted. If it's mounted we
obviously can't use O_EXCL and don't use it.

If it's a data disk, we call blkid which does not use O_EXCL.

> * Does a MEDIA_CHANGE event trigger multiple opens?

Yeah, it can run multiple things against the drive. If it's a data cd
it will run cdrom_id and blkid with the same event.

> I _think_ if udev
> Âopens only once, the event shouldn't be re-generated immediately.

Yeah, but we can't assume only a single open() without making huge changes.

> ÂIt will happen on the next poll interval but it won't be a busy
> Âloop.

This happens without the in-kernel polling enabled.

Kay
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