Re: [PATCH] RISC-V: use __smp_processor_id() instead of smp_processor_id()

[Palmer Dabbelt]

On Thu, 23 Jun 2022 00:43:15 PDT (-0700), xianting.tian@xxxxxxxxxxxxxxxxx wrote:
> Use __smp_processor_id() to avoid check the preemption context when
> CONFIG_DEBUG_PREEMPT enabled, as we will enter crash kernel and no
> return.
>
> Without the patch,
> [  103.781044] sysrq: Trigger a crash
> [  103.784625] Kernel panic - not syncing: sysrq triggered crash
> [  103.837634] CPU1: off
> [  103.889668] CPU2: off
> [  103.933479] CPU3: off
> [  103.939424] Starting crashdump kernel...
> [  103.943442] BUG: using smp_processor_id() in preemptible [00000000] code: sh/346
> [  103.950884] caller is debug_smp_processor_id+0x1c/0x26
> [  103.956051] CPU: 0 PID: 346 Comm: sh Kdump: loaded Not tainted 5.10.113-00002-gce03f03bf4ec-dirty #149
> [  103.965355] Call Trace:
> [  103.967805] [<ffffffe00020372a>] walk_stackframe+0x0/0xa2
> [  103.973206] [<ffffffe000bcf1f4>] show_stack+0x32/0x3e
> [  103.978258] [<ffffffe000bd382a>] dump_stack_lvl+0x72/0x8e
> [  103.983655] [<ffffffe000bd385a>] dump_stack+0x14/0x1c
> [  103.988705] [<ffffffe000bdc8fe>] check_preemption_disabled+0x9e/0xaa
> [  103.995057] [<ffffffe000bdc926>] debug_smp_processor_id+0x1c/0x26
> [  104.001150] [<ffffffe000206c64>] machine_kexec+0x22/0xd0
> [  104.006463] [<ffffffe000291a7e>] __crash_kexec+0x6a/0xa4
> [  104.011774] [<ffffffe000bcf3fa>] panic+0xfc/0x2b0
> [  104.016480] [<ffffffe000656ca4>] sysrq_reset_seq_param_set+0x0/0x70
> [  104.022745] [<ffffffe000657310>] __handle_sysrq+0x8c/0x154
> [  104.028229] [<ffffffe0006577e8>] write_sysrq_trigger+0x5a/0x6a
> [  104.034061] [<ffffffe0003d90e0>] proc_reg_write+0x58/0xd4
> [  104.039459] [<ffffffe00036cff4>] vfs_write+0x7e/0x254
> [  104.044509] [<ffffffe00036d2f6>] ksys_write+0x58/0xbe
> [  104.049558] [<ffffffe00036d36a>] sys_write+0xe/0x16
> [  104.054434] [<ffffffe000201b9a>] ret_from_syscall+0x0/0x2
> [  104.067863] Will call new kernel at ecc00000 from hart id 0
> [  104.074939] FDT image at fc5ee000
> [  104.079523] Bye...
>
> With the patch we can got clear output,
> [   67.740553] sysrq: Trigger a crash
> [   67.744166] Kernel panic - not syncing: sysrq triggered crash
> [   67.809123] CPU1: off
> [   67.865210] CPU2: off
> [   67.909075] CPU3: off
> [   67.919123] Starting crashdump kernel...
> [   67.924900] Will call new kernel at ecc00000 from hart id 0
> [   67.932045] FDT image at fc5ee000
> [   67.935560] Bye...
>
> Fixes: 0e105f1d0037 ("riscv: use hart id instead of cpu id on machine_kexec")
> Co-developed-by: Guo Ren <guoren@xxxxxxxxxx>
> Signed-off-by: Xianting Tian <xianting.tian@xxxxxxxxxxxxxxxxx>
> ---
>  arch/riscv/kernel/machine_kexec.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/machine_kexec.c b/arch/riscv/kernel/machine_kexec.c
> index df8e24559035..86d1b5f9dfb5 100644
> --- a/arch/riscv/kernel/machine_kexec.c
> +++ b/arch/riscv/kernel/machine_kexec.c
> @@ -171,7 +171,7 @@ machine_kexec(struct kimage *image)
>  	struct kimage_arch *internal = &image->arch;
>  	unsigned long jump_addr = (unsigned long) image->start;
>  	unsigned long first_ind_entry = (unsigned long) &image->head;
> -	unsigned long this_cpu_id = smp_processor_id();
> +	unsigned long this_cpu_id = __smp_processor_id();
>  	unsigned long this_hart_id = cpuid_to_hartid_map(this_cpu_id);
>  	unsigned long fdt_addr = internal->fdt_addr;
>  	void *control_code_buffer = page_address(image->control_code_page);

Thanks, this is on for-next.