ad943893d5
Current task of executing crash kexec will be schedule out when panic is triggered by RCU Stall, as it needs to wait rcu completion. It lead to inability to enter the crash system. The implementation of machine_crash_shutdown() is non-standard for RISC-V according to other Arch's implementation(eg, x86, arm64), we need to send IPI to stop secondary harts. [224521.877268] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: [224521.883471] rcu: 0-...0: (3 GPs behind) idle=cfa/0/0x1 softirq=3968793/3968793 fqs=2495 [224521.891742] (detected by 2, t=5255 jiffies, g=60855593, q=328) [224521.897754] Task dump for CPU 0: [224521.901074] task:swapper/0 state:R running task stack: 0 pid: 0 ppid: 0 flags:0x00000008 [224521.911090] Call Trace: [224521.913638] [<ffffffe000c432de>] __schedule+0x208/0x5ea [224521.918957] Kernel panic - not syncing: RCU Stall [224521.923773] bad: scheduling from the idle thread! [224521.928571] CPU: 2 PID: 0 Comm: swapper/2 Kdump: loaded Tainted: G O 5.10.113-yocto-standard #1 [224521.938658] Call Trace: [224521.941200] [<ffffffe00020395c>] walk_stackframe+0x0/0xaa [224521.946689] [<ffffffe000c34f8e>] show_stack+0x32/0x3e [224521.951830] [<ffffffe000c39020>] dump_stack_lvl+0x7e/0xa2 [224521.957317] [<ffffffe000c39058>] dump_stack+0x14/0x1c [224521.962459] [<ffffffe000243884>] dequeue_task_idle+0x2c/0x40 [224521.968207] [<ffffffe000c434f4>] __schedule+0x41e/0x5ea [224521.973520] [<ffffffe000c43826>] schedule+0x34/0xe4 [224521.978487] [<ffffffe000c46cae>] schedule_timeout+0xc6/0x170 [224521.984234] [<ffffffe000c4491e>] wait_for_completion+0x98/0xf2 [224521.990157] [<ffffffe00026d9e2>] __wait_rcu_gp+0x148/0x14a [224521.995733] [<ffffffe0002761c4>] synchronize_rcu+0x5c/0x66 [224522.001307] [<ffffffe00026f1a6>] rcu_sync_enter+0x54/0xe6 [224522.006795] [<ffffffe00025a436>] percpu_down_write+0x32/0x11c [224522.012629] [<ffffffe000c4266a>] _cpu_down+0x92/0x21a [224522.017771] [<ffffffe000219a0a>] smp_shutdown_nonboot_cpus+0x90/0x118 [224522.024299] [<ffffffe00020701e>] machine_crash_shutdown+0x30/0x4a [224522.030483] [<ffffffe00029a3f8>] __crash_kexec+0x62/0xa6 [224522.035884] [<ffffffe000c3515e>] panic+0xfa/0x2b6 [224522.040678] [<ffffffe0002772be>] rcu_sched_clock_irq+0xc26/0xcb8 [224522.046774] [<ffffffe00027fc7a>] update_process_times+0x62/0x8a [224522.052785] [<ffffffe00028d522>] tick_sched_timer+0x9e/0x102 [224522.058533] [<ffffffe000280c3a>] __hrtimer_run_queues+0x16a/0x318 [224522.064716] [<ffffffe0002812ec>] hrtimer_interrupt+0xd4/0x228 [224522.070551] [<ffffffe0009a69b6>] riscv_timer_interrupt+0x3c/0x48 [224522.076646] [<ffffffe000268f8c>] handle_percpu_devid_irq+0xb0/0x24c [224522.083004] [<ffffffe00026428e>] __handle_domain_irq+0xa8/0x122 [224522.089014] [<ffffffe00062f954>] riscv_intc_irq+0x38/0x60 [224522.094501] [<ffffffe000201bd4>] ret_from_exception+0x0/0xc [224522.100161] [<ffffffe000c42146>] rcu_eqs_enter.constprop.0+0x8c/0xb8 With the patch, it can enter crash system when RCU Stall occur. Fixes: e53d28180d4d ("RISC-V: Add kdump support") Signed-off-by: Xianting Tian <xianting.tian@linux.alibaba.com> Link: https://lore.kernel.org/r/20220811074150.3020189-4-xianting.tian@linux.alibaba.com Cc: stable@vger.kernel.org Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.