From: Frederic Weisbecker <frederic@kernel.org>
To: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
rcu@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Mark Rutland <mark.rutland@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
paulmck@kernel.org, mtosatti <mtosatti@redhat.com>
Subject: Re: Question WRT early IRQ/NMI entry code
Date: Tue, 30 Nov 2021 13:05:11 +0100 [thread overview]
Message-ID: <20211130120511.GB599355@lothringen> (raw)
In-Reply-To: <8719ad46cc29a2c5d7baac3c35770e5460ab8d5c.camel@redhat.com>
On Tue, Nov 30, 2021 at 12:28:41PM +0100, Nicolas Saenz Julienne wrote:
> Hi All,
> while going over the IRQ/NMI entry code I've found a small 'inconsistency':
> while in the IRQ entry path, we inform RCU of the context change *before*
> incrementing the preempt counter, the opposite happens for the NMI entry
> path. This applies to both arm64 and x86[1].
>
> Actually, rcu_nmi_enter() — which is also the main RCU context switch function
> for the IRQ entry path — uses the preempt counter to verify it's not in NMI
> context. So it would make sense to assume all callers have the same updated
> view of the preempt count, which isn't true ATM.
>
> I'm sure there an obscure/non-obvious reason for this, right?
At least I can't find an immediate reason for it either :-)
Thanks!
next prev parent reply other threads:[~2021-11-30 12:05 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-30 11:28 Question WRT early IRQ/NMI entry code Nicolas Saenz Julienne
2021-11-30 12:05 ` Frederic Weisbecker [this message]
2021-11-30 12:50 ` Mark Rutland
2021-11-30 13:47 ` Thomas Gleixner
2021-11-30 14:13 ` Steven Rostedt
2021-11-30 22:31 ` [PATCH] Documentation: Fill the gaps about entry/noinstr constraints Thomas Gleixner
2021-12-01 10:56 ` Mark Rutland
2021-12-01 18:14 ` Thomas Gleixner
2021-12-01 18:23 ` Mark Rutland
2021-12-01 20:28 ` Thomas Gleixner
2021-12-01 20:35 ` [PATCH v2] " Thomas Gleixner
2021-12-02 10:03 ` Mark Rutland
2021-12-03 20:08 ` Paul E. McKenney
2021-12-13 10:36 ` Nicolas Saenz Julienne
2021-12-13 16:41 ` Paul E. McKenney
2021-12-04 3:48 ` Randy Dunlap
2021-12-06 17:36 ` Mark Rutland
2021-12-06 17:53 ` Paul E. McKenney
2021-12-06 21:24 ` Randy Dunlap
2021-12-06 21:36 ` Paul E. McKenney
2021-11-30 15:13 ` Question WRT early IRQ/NMI entry code Nicolas Saenz Julienne
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