[PATCHv3 0/4] arm64: Fixes RCU deadlock due to a mistaken

[Pingfan Liu]

It was [PATCHv2 1/5] arm64/entry-common: push the judgement of nmi ahead
[1], but as discussion, I found it hit a deadlock, so change subject in
v3.

Linux kernel places strict semantics between NMI and maskable interrupt.
So does the RCU component, else deadlock may happen.

The current arm64 entry code can partially breach this rule through
calling rcu_nmi_enter() in pNMI conext without calling __nmi_enter().
Finally, it calls __rcu_irq_enter_check_tick() trying to hold
raw_spin_lock_rcu_node(rdp->mynode), but this spinlock can already been
held by a task running note_gp_changes()->raw_spin_trylock_rcu_node(rnp).
Then deadlock happens.

The organization of this series:
  [1/4] aims to fix this bug
  [2-3/4] ease the implementation of [1/4]
  [4/4] is a cleanup

To do:
  Does arm need to handle pNMI as arm64?

v2 -> v3:
  drop handle_arch_nmi interface

[1]: https://lore.kernel.org/linux-arm-kernel/20210924132837.45994-2-kernelfans@gmail.com/

Cc: Mark Rutland <mark.rutland at arm.com>
Cc: Paul E. McKenney <paulmck at kernel.org>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Will Deacon <will at kernel.org>
Cc: Marc Zyngier <maz at kernel.org>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Joey Gouly <joey.gouly at arm.com>
Cc: Sami Tolvanen <samitolvanen at google.com>
Cc: Julien Thierry <julien.thierry at arm.com>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Yuichi Ito <ito-yuichi at fujitsu.com>
Cc: rcu at vger.kernel.org
To: linux-arm-kernel at lists.infradead.org

Pingfan Liu (4):
  arm64: entry: judge nmi ealier to avoid deadlock in RCU
  arm64: entry: distinguish pNMI earlier in el0 interrupt
  irqchip: GICv3: expose pNMI discriminator
  arm64: entry: remove pNMI judgement in __el1_interrupt() path

 arch/arm64/kernel/entry-common.c | 55 +++++++++++++++++++++-----------
 arch/arm64/kernel/irq.c          | 15 +++++++++
 drivers/irqchip/irq-gic-v3.c     | 16 ++++++----
 3 files changed, 62 insertions(+), 24 deletions(-)

-- 
2.31.1