All of lore.kernel.org
 help / color / mirror / Atom feed
From: David Howells <dhowells@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: dhowells@redhat.com, Thomas Gleixner <tglx@linutronix.de>,
	John Stultz <john.stultz@linaro.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: Apparent backward time travel in timestamps on file creation
Date: Thu, 30 Mar 2017 23:22:17 +0100	[thread overview]
Message-ID: <26743.1490912537@warthog.procyon.org.uk> (raw)
In-Reply-To: <CA+55aFw+OVhOCu3y7vmqH7P9dP=CNjtgowQ1FNge2Y6oGgh_8w@mail.gmail.com>

Linus Torvalds <torvalds@linux-foundation.org> wrote:

> The "is it in sync with gettimeofday()" is interesting too, even if
> the answer is that you don't expect it to be _perfectly_ in sync. A
> test that just reports maximum slop might be an interesting test, and
> could show real problems (maybe bad network time synchronization, but
> maybe actual bugs in our internal xtime handling even for local
> filesystems!).

I wonder if multi-cpu systems might show interesting differences between CPUs
too.  I would hope not since xtime is based on a global variable.

> And then if your tool starts reporting times that are off by seconds
> or minutes, people might say "Hey, that's not right.." and find
> something.

More likely never see it as the output is hidden away by xfstests.  Probably
xfstests needs to gain some way of lending prominence to information of this
type.

David

  parent reply	other threads:[~2017-03-30 22:22 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-30 17:30 Apparent backward time travel in timestamps on file creation David Howells
2017-03-30 18:07 ` Linus Torvalds
2017-03-30 18:49 ` John Stultz
2017-03-30 19:35 ` David Howells
2017-03-30 19:52   ` Linus Torvalds
2017-03-30 20:04     ` Linus Torvalds
2017-03-30 20:13     ` David Howells
2017-03-30 20:16       ` David Lang
2017-03-30 21:13       ` Linus Torvalds
2017-03-31 12:35         ` Bob Peterson
2017-03-30 22:22       ` David Howells [this message]
2017-03-30 20:03   ` John Stultz
2017-03-30 20:06     ` Linus Torvalds

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=26743.1490912537@warthog.procyon.org.uk \
    --to=dhowells@redhat.com \
    --cc=john.stultz@linaro.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=tglx@linutronix.de \
    --cc=torvalds@linux-foundation.org \
    /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
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.