linux-kernel - Re: [PATCH 4.19 011/120] tcp: annotate tp->copied

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Message-ID: <YFB/CBeDBiolOxDD@kroah.com>
Date:   Tue, 16 Mar 2021 10:48:56 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Pavel Machek <pavel@...x.de>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 4.19 011/120] tcp: annotate tp->copied_seq lockless reads

On Tue, Mar 16, 2021 at 10:41:37AM +0100, Pavel Machek wrote:
> Hi!
> 
> > From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > 
> > From: Eric Dumazet <edumazet@...gle.com>
> 
> Two From: fields here.

This is a side-affect of me using git-send-email to talk to the remote
smtp server directly instead of using my local email server.  This was
done to increase the speed of sending these patches out as
git-send-email can pipeline messages instead of having msmtp do a
setup/send/teardown on every individual message sent.

These are not in the patches themselves and I will work to figure out
if this can be fixed.  Gotta be a setting somewhere...

> 
> > [ Upstream commit 7db48e983930285b765743ebd665aecf9850582b ]
> > 
> > There are few places where we fetch tp->copied_seq while
> > this field can change from IRQ or other cpu.
> 
> And there are few such places even after the patch is applied; I
> quoted them below.
> 
> Doing addition to variable without locking... is kind of
> interesting. Are you sure it is okay?

Why isn't it?

thanks,

greg k-h