linux-kernel - Re: [PATCH] RISC-V: use __smp_processor_id() instead of smp_processor

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Message-ID: <mhng-3d40a456-c1da-41c8-9234-0ea16a2c7d09@palmer-mbp2014>
Date:   Thu, 11 Aug 2022 09:05:18 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     xianting.tian@...ux.alibaba.com
CC:     Paul Walmsley <paul.walmsley@...ive.com>, aou@...s.berkeley.edu,
        alex@...ti.fr, liaochang1@...wei.com, mick@....forth.gr,
        guoren@...nel.org, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, xianting.tian@...ux.alibaba.com
Subject:     Re: [PATCH] RISC-V: use __smp_processor_id() instead of smp_processor_id()

On Thu, 11 Aug 2022 08:45:18 PDT (-0700), Palmer Dabbelt wrote:
> On Thu, 23 Jun 2022 00:43:15 PDT (-0700), xianting.tian@...ux.alibaba.com 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@...nel.org>
>> Signed-off-by: Xianting Tian <xianting.tian@...ux.alibaba.com>
>> ---
>>  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.

Connor pointed out that there's a series with more fixes, so I'm going 
to take that instead.