From: Shmulik Hen <shmulik@trego•co.il>
To: Eric Dumazet <eric.dumazet@gmail•com>
Cc: netdev@vger•kernel.org, Shmulik Hen <shmulik.hen@gmail•com>,
Ben Hutchings <bhutchings@solarflare•com>,
shemminger@vyatta•com
Subject: Re: System blocks (hangs) on ifconfig up
Date: Mon, 13 Dec 2010 15:11:25 +0200 [thread overview]
Message-ID: <4D061B7D.9050805@trego.co.il> (raw)
In-Reply-To: <1292243832.2759.1.camel@edumazet-laptop>
On 12/13/2010 02:37 PM, Eric Dumazet wrote:
>>
>> But why does this happen only the second time I run ifconfig up?
>> How come the entire system is totally frozen?
>> I can't even switch to other applications running. If I run 'top' in another
>> console, it stops refreshing for the entire period.
>>
>> I'll try to explain better;
>> The driver I'm referring to is part of an embedded system development kit.
>> It runs on the controlling side, which may be a PC or some Linux embedded
>> system. It exposes a virtual interface that allows to communicate via
>> ethernet connection to a remote board, and performs the firmware download
>> to that board.
>> Unfortunately, the firmware download stage is done during dev->open() of
>> this virtual interface. The call to wait_event_interruptible_timeout()
>> is there to make sure the boot process of the remote board is complete via a
>> message. If all goes well the first time, there is no delay, but if the
>> operation
>> fails for any reason the first time, and a second attempt is made (another
>> ifconfig up), we see the freezing.
>>
>> Since this driver is (mostly) closed source, I had to try and reproduce
>> the situation
>> in an all open-source driver - this is the sample code I attached to my
>> original
>> message. The call to mdelay() there is meant to simulate the delay of
>> the original
>> driver - it schedules.
>>
> mdelay() does a busy wait. If you are not SMP, this means a 'freeze'
>
> If you want to schedule, you should use msleep()
Correct - my bad. When I use msleep() in the sample code there is no freeze.
But I still don't get it - when using mdelay(), why does the system
freeze only
the second time but not in the first time?
And what about wait_event_interruptible_timeout()? surely it doesn't
do a busy loop - I can see the source calling schedule().
next prev parent reply other threads:[~2010-12-13 13:11 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-12 15:00 System blocks (hangs) on ifconfig up Shmulik Hen
2010-12-12 23:03 ` Ben Hutchings
2010-12-13 9:14 ` Shmulik Hen
2010-12-13 12:37 ` Eric Dumazet
2010-12-13 13:11 ` Shmulik Hen [this message]
2010-12-12 23:29 ` Stephen Hemminger
-- strict thread matches above, loose matches on Subject: below --
2010-12-12 15:08 Shmulik Hen
2010-12-12 20:29 ` Eric Dumazet
2010-12-12 20:53 ` Eric Dumazet
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