linux-kernel - RE: [RFC] WRITE_ONCE

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Message-ID: <3a6f974efad4453e9af7a3152ca0bbce@AcuMS.aculab.com>
Date:   Tue, 21 Apr 2020 08:00:48 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Petko Manolov' <petko.manolov@...sulko.com>,
        "Paul E. McKenney" <paulmck@...nel.org>
CC:     LKML <linux-kernel@...r.kernel.org>
Subject: RE: [RFC] WRITE_ONCE_INC() and friends

From: Petko Manolov
> Sent: 20 April 2020 17:32
...
> > But one downside of declaring variables volatile is that it can prevent KCSAN
> > from spotting violations of the concurrency design for those variables.
> 
> Which would be unfortunate.
> 
> I just wish there was C type declaration that would force the compiler to do
> what READ/WRITE_ONCE() does now, but i also know this is too naive... :)

It does, it is called 'volatile'.

All READ_ONCE() does is force the access through a volatile pointer.

The thing to do is mark the structure elements 'volatile'
rather than using a 'pointer to volatile structure'.

I'm sure KASAN could be taught about volatile structure members.

	David.

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