linux-kernel - Re: [PATCH -printk] printk, tracing: fix console tracepoint

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20220711205319.1aa0d875@gandalf.local.home>
Date:   Mon, 11 Jul 2022 20:53:19 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     Marco Elver <elver@...gle.com>,
        John Ogness <john.ogness@...utronix.de>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        Thomas Gleixner <tglx@...utronix.de>,
        Johannes Berg <johannes.berg@...el.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Naresh Kamboju <naresh.kamboju@...aro.org>,
        Linux Kernel Functional Testing <lkft@...aro.org>
Subject: Re: [PATCH -printk] printk, tracing: fix console tracepoint

On Mon, 11 Jul 2022 17:21:28 -0700
"Paul E. McKenney" <paulmck@...nel.org> wrote:

> On x86, both srcu_read_lock() and srcu_read_unlock() should be OK from
> NMI context, give or take their use of lockdep.  Which is why we have
> srcu_read_lock_notrace() and srcu_read_unlock_notrace(), which do not
> use lockdep.  Which __DO_TRACE() does in fact invoke.  Ah, but you have
> this: "WARN_ON_ONCE(rcuidle && in_nmi())".
> 
> Because all the world is not an x86.

But since NMIs are architecture specific, we could change that to:

	WARN_ON_ONCE(!srcu_nmi_safe && rcuidle && in_nmi());

and add a srcu_nmi_safe constant or macro that is 1 on architectures that
srcu is safe in NMI and 0 otherwise.

Or do we care if a tracepoint happens in those architectures where it is
not safe. We could then just do:

	if (!srcu_nmi_safe && rcuidle && in_nmi())
		return;

and just skip tracepoints that are marked rcu_idle and happen within NMI.

-- Steve