Re: [PATCH dovetail v5 03/12] riscv: irq_pipeline: enable hard IRQs during in-band trap handling

Until mark_trap_entry/exit do call oob_trap_notify/unwind to forward the
event to the companion core, this code can be merged into the previous
patch introducing the interrupt pipeline.

Tobias Schaffner <[email protected]> writes:

> When running with interrupt pipelining, re-enable hard interrupts
> while handling traps on the in-band stage so that out-of-band events
> can be delivered promptly.
>
> Signed-off-by: Tobias Schaffner <[email protected]>
> ---
>  arch/riscv/kernel/traps.c | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
>
> diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
> index 267b8ec5a1bf..5b84e1ff0eeb 100644
> --- a/arch/riscv/kernel/traps.c
> +++ b/arch/riscv/kernel/traps.c
> @@ -112,10 +112,30 @@ void die(struct pt_regs *regs, const char *str)
>  		make_task_dead(SIGSEGV);
>  }
>  
> +static __always_inline
> +bool mark_trap_entry(int signo, struct pt_regs *regs)
> +{
> +	if (likely(running_inband())) {
> +		hard_cond_local_irq_enable();
> +		return true;
> +	}
> +
> +	return false;
> +}
> +
> +static __always_inline
> +void mark_trap_exit(int signo, struct pt_regs *regs)
> +{
> +	hard_cond_local_irq_disable();
> +}
> +
>  void do_trap(struct pt_regs *regs, int signo, int code, unsigned long addr)
>  {
>  	struct task_struct *tsk = current;
>  
> +	if (!mark_trap_entry(signo, regs))
> +		return;
> +
>  	if (show_unhandled_signals && unhandled_signal(tsk, signo)
>  	    && printk_ratelimit()) {
>  		pr_info("%s[%d]: unhandled signal %d code 0x%x at 0x" REG_FMT,
> @@ -127,6 +147,8 @@ void do_trap(struct pt_regs *regs, int signo, int code, unsigned long addr)
>  	}
>  
>  	force_sig_fault(signo, code, (void __user *)addr);
> +
> +	mark_trap_exit(signo, regs);
>  }
>  
>  static void do_trap_error(struct pt_regs *regs, int signo, int code,
> @@ -137,6 +159,12 @@ static void do_trap_error(struct pt_regs *regs, int signo, int code,
>  	if (user_mode(regs)) {
>  		do_trap(regs, signo, code, addr);
>  	} else {
> +		/*
> +		 * Dovetail: If we trapped from kernel space, either
> +		 * we can fix up the situation, or we can't and we may
> +		 * happily crash with hard irqs off. Either way, don't
> +		 * bother.
> +		 */
>  		if (!fixup_exception(regs))
>  			die(regs, str);
>  	}

-- 
Philippe.