linux-kernel - Re: [PATCH v2 rcu 0/8] NMI-safe SRCU reader API

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Date:   Wed, 19 Oct 2022 13:19:53 +0206
From:   John Ogness <john.ogness@...utronix.de>
To:     paulmck@...nel.org
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com, rostedt@...dmis.org, tglx@...utronix.de,
        pmladek@...e.com, Frederic Weisbecker <frederic@...nel.org>
Subject: Re: [PATCH v2 rcu 0/8] NMI-safe SRCU reader API

On 2022-10-18, "Paul E. McKenney" <paulmck@...nel.org> wrote:
> And the v6.1-rc1 stack is now at srcunmisafe.2022.10.18b.

Thanks!

I guess the kernel test robot will catch this, but if you checkout
commit 79c95dc428ad ("arch/x86: Add ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
Kconfig option") and build for x86_64, you will get:

x86_64-linux-gnu-ld: kernel/rcu/srcutree.o: in function `srcu_gp_start_if_needed':
srcutree.c:(.text+0x133a): undefined reference to `__srcu_read_lock_nmisafe'
x86_64-linux-gnu-ld: srcutree.c:(.text+0x1490): undefined reference to `__srcu_read_unlock_nmisafe'
x86_64-linux-gnu-ld: kernel/rcu/srcutree.o: in function `srcu_barrier':
srcutree.c:(.text+0x1b03): undefined reference to `__srcu_read_lock_nmisafe'
x86_64-linux-gnu-ld: srcutree.c:(.text+0x1b38): undefined reference to `__srcu_read_unlock_nmisafe'

Note that this error is fixed with a later commit:

commit c2d158a284ab ("srcu: Debug NMI safety even on archs that don't
require it").

This does not affect what I am working on, so feel free to take care of
it whenever it fits your schedule.

John Ogness