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SubjectRe: [patch V3 01/23] rcu: Dont acquire lock in NMI handler in rcu_nmi_enter_common()
On Fri, Mar 20, 2020 at 06:59:57PM +0100, Thomas Gleixner wrote:
> From: "Paul E. McKenney" <paulmck@kernel.org>
>
> The rcu_nmi_enter_common() function can be invoked both in interrupt
> and NMI handlers. If it is invoked from process context (as opposed
> to userspace or idle context) on a nohz_full CPU, it might acquire the
> CPU's leaf rcu_node structure's ->lock. Because this lock is held only
> with interrupts disabled, this is safe from an interrupt handler, but
> doing so from an NMI handler can result in self-deadlock.
>
> This commit therefore adds "irq" to the "if" condition so as to only
> acquire the ->lock from irq handlers or process context, never from
> an NMI handler.
>
> Fixes: 5b14557b073c ("rcu: Avoid tick_dep_set_cpu() misordering")
> Reported-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> Link: https://lkml.kernel.org/r/20200313024046.27622-1-paulmck@kernel.org

Reviewed-by: Frederic Weisbecker <frederic@kernel.org>

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