LKML Archive on
help / color / mirror / Atom feed
From: Tejun Heo <>
To: Alan Stern <>
Cc: Jens Axboe <>,
	Kernel development list <>
Subject: Re: [PATCH 1/2] Add round_jiffies_up and related routines
Date: Wed, 05 Nov 2008 12:33:19 +0900	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Alan Stern wrote:
> This patch (as1158) adds round_jiffies_up() and friends.  These
> routines work like the analogous round_jiffies() functions, except
> that they will never round down.
> The new routines will be useful for timeouts where we don't care
> exactly when the timer expires, provided it doesn't expire too soon.
> Signed-off-by: Alan Stern <>

Heh... I have exactly the same patches but mines were named

> +	unsigned long j0 = jiffies;
> +
> +	barrier();	/* Prevent the compiler from aliasing j0 and jiffies */
> +	return round_jiffies_common(j + j0, cpu, false) - j0;

jiffies is volatile.  No need for explicit barrier, but this part is
necessary for correct operation as if jiffies go up by two the
calculation will wrap and the returned value will be very large.  I
think this fix deserves a separate patch and proper explanation.



  reply	other threads:[~2008-11-05  3:34 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-11-04 16:15 Alan Stern
2008-11-05  3:33 ` Tejun Heo [this message]
2008-11-05 16:20   ` Alan Stern
2008-11-05 19:11     ` Jens Axboe
2008-11-05 21:18       ` [PATCH 1/2 ver 2] " Alan Stern
2008-11-06  7:42         ` Jens Axboe

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:

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

  git send-email \ \ \ \ \ \
    --subject='Re: [PATCH 1/2] Add round_jiffies_up and related routines' \

* 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).