Re: [PATCH v2] riscv: disable local interrupts and stop other CPUs before reboot/shutdown

[Troy Mitchell]

On Tue Mar 17, 2026 at 4:48 PM CST, Troy Mitchell wrote:
> Currently, the RISC-V implementation of machine_restart(), machine_halt(),
> and machine_power_off() invokes the kernel teardown chains (e.g.,
> do_kernel_restart()) with local interrupts enabled and other CPUs still
> running.
>
> This implementation fails to provide a deterministic execution environment
> for registered handlers in the restart or power-off notifier chains. These
> chains are intended to be executed in a strict atomic and single-threaded
> context.
>
> Specifically, under CONFIG_PREEMPT_RCU, rcu_read_lock() does not increment
> the preempt_count. If local interrupts remain enabled, the environment
> is not guaranteed to be atomic. This can lead to a context misidentification
> within generic kernel teardown code, causing it to incorrectly enter
> non-atomic paths (such as attempting to acquire sleeping locks), which
> results in fatal "scheduling while atomic" splats or system hangs.
>
> Additionally, stopping other CPUs ensures the primary CPU has exclusive
> access to the hardware state during the final teardown phase, preventing
> unpredictable interference from other active cores.
>
> Align RISC-V with other major architectures by disabling local interrupts
> and stopping other CPUs at the beginning of the shutdown sequences. This
> guarantees the architectural expectations of the kernel's restart and
> power-off handlers are met.
>
> Signed-off-by: Troy Mitchell <troy.mitchell@xxxxxxxxx>
Sry I forgot to add Aurelien's tag [1]

Link: https://lore.kernel.org/all/abEP80FoCn4S4-WG@xxxxxxxxxxx/ [1]