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From:   Heiko =?ISO-8859-1?Q?St=FCbner?= <heiko@sntech.de>
To:     paul.walmsley@sifive.com, palmer@dabbelt.com,
        aou@eecs.berkeley.edu, anup@brainfault.org, guoren@kernel.org,
        mick@ics.forth.gr, alexandre.ghiti@canonical.com,
        Xianting Tian <xianting.tian@linux.alibaba.com>
Cc:     linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        crash-utility@redhat.com, huanyi.xj@alibaba-inc.com,
        heinrich.schuchardt@canonical.com, k-hagio-ab@nec.com,
        hschauhan@nulltrace.org,
        Xianting Tian <xianting.tian@linux.alibaba.com>
Subject: Re: [PATCH 2/5] RISC-V: use __smp_processor_id() instead of smp_processor_id()
Date:   Fri, 22 Jul 2022 09:17:43 +0200
Message-ID: <2189907.iZASKD2KPV@diego>
In-Reply-To: <20220717101323.370245-3-xianting.tian@linux.alibaba.com>
References: <20220717101323.370245-1-xianting.tian@linux.alibaba.com> <20220717101323.370245-3-xianting.tian@linux.alibaba.com>
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Am Sonntag, 17. Juli 2022, 12:13:20 CEST schrieb Xianting Tian:
> 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")
> Reviewed-by: Guo Ren <guoren@kernel.org>
> Signed-off-by: Xianting Tian <xianting.tian@linux.alibaba.com>

Reviewed-by: Heiko Stuebner <heiko@sntech.de>