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From: Johannes Berg <johannes@sipsolutions.net>
To: Vincent Whitchurch <Vincent.Whitchurch@axis.com>,
	 "anton.ivanov@cambridgegreys.com"
	<anton.ivanov@cambridgegreys.com>,
	"richard@nod.at" <richard@nod.at>
Cc: "linux-um@lists.infradead.org" <linux-um@lists.infradead.org>,
	 "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	kernel <kernel@axis.com>
Subject: Re: [PATCH] um: time-travel: fix time going backwards
Date: Wed, 25 Oct 2023 22:41:38 +0200	[thread overview]
Message-ID: <1f38d92435cc4f3a5e8d17dff3da9e34be2e6f24.camel@sipsolutions.net> (raw)
In-Reply-To: <68b18065d8be905c25522bd3f5a9b46dbe3a976d.camel@sipsolutions.net>

On Wed, 2023-10-25 at 22:02 +0200, Johannes Berg wrote:
> On Wed, 2023-10-25 at 21:51 +0200, Johannes Berg wrote:
> > On Wed, 2023-10-25 at 11:55 +0000, Vincent Whitchurch wrote:
> > > On Mon, 2023-10-23 at 09:33 +0200, Johannes Berg wrote:
> > > > Do you have a specific workload that tends to reproduce this?
> > > 
> > > I've been seeing it when running roadtest, but it's easily reproducible
> > > without that by using the attached config and the following program as
> > > init.
> > > 
> > >   cp repro.config .config
> > >   make ARCH=um olddefconfig all
> > >   gcc -Wall -static -o repro repro.c
> > >   ./linux time-travel init=$PWD/repro rootfstype=hostfs
> 
> Ohhh.
> 
> Pure "time-travel" is actually something I hardly think about these
> days, we mostly use time-travel=inf-cpu (or =ext).
> 
> That makes sense, here you actually *can* get interrupted. I'll need to
> dig into what happens though.

I just sent a patch, please take a look. It does seem to fix it - at
least I got bored of waiting after running your test program for a few
minutes :)

johannes

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WARNING: multiple messages have this Message-ID (diff)
From: Johannes Berg <johannes@sipsolutions.net>
To: Vincent Whitchurch <Vincent.Whitchurch@axis.com>,
	"anton.ivanov@cambridgegreys.com"
	<anton.ivanov@cambridgegreys.com>,
	"richard@nod.at" <richard@nod.at>
Cc: "linux-um@lists.infradead.org" <linux-um@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	kernel <kernel@axis.com>
Subject: Re: [PATCH] um: time-travel: fix time going backwards
Date: Wed, 25 Oct 2023 22:41:38 +0200	[thread overview]
Message-ID: <1f38d92435cc4f3a5e8d17dff3da9e34be2e6f24.camel@sipsolutions.net> (raw)
In-Reply-To: <68b18065d8be905c25522bd3f5a9b46dbe3a976d.camel@sipsolutions.net>

On Wed, 2023-10-25 at 22:02 +0200, Johannes Berg wrote:
> On Wed, 2023-10-25 at 21:51 +0200, Johannes Berg wrote:
> > On Wed, 2023-10-25 at 11:55 +0000, Vincent Whitchurch wrote:
> > > On Mon, 2023-10-23 at 09:33 +0200, Johannes Berg wrote:
> > > > Do you have a specific workload that tends to reproduce this?
> > > 
> > > I've been seeing it when running roadtest, but it's easily reproducible
> > > without that by using the attached config and the following program as
> > > init.
> > > 
> > >   cp repro.config .config
> > >   make ARCH=um olddefconfig all
> > >   gcc -Wall -static -o repro repro.c
> > >   ./linux time-travel init=$PWD/repro rootfstype=hostfs
> 
> Ohhh.
> 
> Pure "time-travel" is actually something I hardly think about these
> days, we mostly use time-travel=inf-cpu (or =ext).
> 
> That makes sense, here you actually *can* get interrupted. I'll need to
> dig into what happens though.

I just sent a patch, please take a look. It does seem to fix it - at
least I got bored of waiting after running your test program for a few
minutes :)

johannes

  reply	other threads:[~2023-10-25 20:41 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-10-20 14:47 [PATCH] um: time-travel: fix time going backwards Vincent Whitchurch
2023-10-20 14:47 ` Vincent Whitchurch
2023-10-23  7:08 ` Vincent Whitchurch
2023-10-23  7:08   ` Vincent Whitchurch
2023-10-23  7:33   ` Johannes Berg
2023-10-23  7:33     ` Johannes Berg
2023-10-25 11:55     ` Vincent Whitchurch
2023-10-25 11:55       ` Vincent Whitchurch
2023-10-25 19:51       ` Johannes Berg
2023-10-25 19:51         ` Johannes Berg
2023-10-25 20:02         ` Johannes Berg
2023-10-25 20:02           ` Johannes Berg
2023-10-25 20:41           ` Johannes Berg [this message]
2023-10-25 20:41             ` Johannes Berg

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