[PATCH] powerpc/64s: prevent recursive replay_soft_interrupts causing superfluous interrupt

[Michael Ellerman]

On Sat, 23 Jan 2021 16:12:44 +1000, Nicholas Piggin wrote:
> When an asynchronous interrupt calls irq_exit, it checks for softirqs
> that may have been created, and runs them. Running softirqs enables
> local irqs, which can replay pending interrupts causing recursion in
> replay_soft_interrupts. This abridged trace shows how this can occur:
> 
> ! NIP replay_soft_interrupts
>   LR  interrupt_exit_kernel_prepare
>   Call Trace:
>     interrupt_exit_kernel_prepare (unreliable)
>     interrupt_return
>   --- interrupt: ea0 at __rb_reserve_next
>   NIP __rb_reserve_next
>   LR __rb_reserve_next
>   Call Trace:
>     ring_buffer_lock_reserve
>     trace_function
>     function_trace_call
>     ftrace_call
>     __do_softirq
>     irq_exit
>     timer_interrupt
> !   replay_soft_interrupts
>     interrupt_exit_kernel_prepare
>     interrupt_return
>   --- interrupt: ea0 at arch_local_irq_restore
> 
> [...]

Applied to powerpc/fixes.

[1/1] powerpc/64s: prevent recursive replay_soft_interrupts causing superfluous interrupt
      https://git.kernel.org/powerpc/c/4025c784c573cab7e3f84746cc82b8033923ec62

cheers