LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Andrew Bird <ajb@spheresystems.co.uk>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Spinlock debugging
Date: Tue, 12 Sep 2006 08:47:39 +0100	[thread overview]
Message-ID: <200609120847.39655.ajb@spheresystems.co.uk> (raw)
In-Reply-To: <1157995492.23085.191.camel@localhost.localdomain>

Alan
	thanks that did the trick. 
One further question, on the later kernels 2.6.17+, I don't have low_latency 
set. Can I still guarantee that after calling tty_flip_buffer_push() I have 
made space in the tty for my buffer? For example, is this legal? 

// in interrupt handler

   if(tty_buffer_request_room(tty, size) < size) {

      spin_unlock(&dc->lock);
      spin_unlock(&port->lock);

      tty_flip_buffer_push(tty);

      spin_lock(&port->lock);
      spin_lock(&dc->lock);

  }
  tty_insert_flip_string(tty, buf, size);
   
Thanks


Andrew

On Monday 11 September 2006 18:24, Alan Cox wrote:
> Ar Llu, 2006-09-11 am 17:38 +0100, ysgrifennodd Andrew Bird:
> > Alan
> > 	Yes, I have low_latency set for kernels lower than 2.6.17. I'm currently
> > testing using 2.6.15. When you mention 'write method for flow control' do
> > you mean for software XON/XOFF etc?
>
> Yes
>
> Basically in low_latency the following is valid
>
>
> 	driver receives bytes
> 		flush_to_ldisc
> 			ldisc calls driver write methods
>
>
> That means if you have a shared lock for read/write you want to drop it
> after you've bashed the hardware and before you flush_to_ldisc. Remember
> the IRQ handler is not re-entrant so another IRQ of the same number
> won't cause further I/O and out of order receives.
>
> Alan

  reply	other threads:[~2006-09-12  7:47 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-09-11 15:32 Andrew Bird (Sphere Systems)
2006-09-11 16:36 ` Alan Cox
2006-09-11 16:38   ` Andrew Bird
2006-09-11 17:24     ` Alan Cox
2006-09-12  7:47       ` Andrew Bird [this message]
2006-09-12 13:43         ` Alan Cox
2006-09-12 13:31           ` Sergei Organov
2006-09-12 14:04             ` Alan Cox

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=200609120847.39655.ajb@spheresystems.co.uk \
    --to=ajb@spheresystems.co.uk \
    --cc=alan@lxorguk.ukuu.org.uk \
    --cc=linux-kernel@vger.kernel.org \
    --subject='Re: Spinlock debugging' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).