Messages in this thread | | | Subject | Re: [RFC PATCH] mce: don't not enable IRQ in wait_for_panic() | From | Wu Bo <> | Date | Mon, 21 Sep 2020 19:35:50 +0800 |
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On 2020/9/17 18:37, Wu Bo wrote: > In my virtual machine (have 4 cpus), Use mce_inject to inject errors > into the system. After mce-inject injects an uncorrectable error, > there is a probability that the virtual machine is not reset immediately, > but hangs for more than 3000 seconds, and appeared unable to > handle kernel paging request. > > The analysis reasons are as follows: > 1) MCE appears on all CPUs, Currently all CPUs are in the NMI interrupt > context. cpu0 is the first to seize the opportunity to run panic > routines, and panic event should stop the other processors before > do ipmi flush_messages(). but cpu1, cpu2 and cpu3 has already > in NMI interrupt context, So the Second NMI interrupt(IPI) > will not be processed again by cpu1, cpu2 and cpu3. > At this time, cpu1,cpu2 and cpu3 did not stopped. > > 2) cpu1, cpu2 and cpu3 are waitting for cpu0 to finish the panic process. > if a timeout waiting for other CPUs happened, do wait_for_panic(), > the irq is enabled in the wait_for_panic() function. > > 3) ipmi IRQ occurs on the cpu3, and the cpu0 is doing the panic, > they have the opportunity to call the smi_event_handler() > function concurrently. the ipmi IRQ affects the panic process of cpu0. > > CPU0 CPU3 > > |-nmi_handle do mce_panic |-nmi_handle do_machine_check > | | > |-panic() |-wait_for_panic() > | | > |-stop other cpus ---- NMI ------> (Ignore, already in nmi interrupt) > | | > |-notifier call(ipmi panic_event) |<-ipmi IRQ occurs > | | > \|/ \|/ > do smi_event_handler() do smi_event_handler() > > My understanding is that panic() runs with only one operational CPU > in the system, other CPUs should be stopped, if other CPUs does not stop, > at least IRQ interrupts should be disabled. The x86 architecture, > disable IRQ interrupt will not affect IPI when do mce panic, > because IPI is notified through NMI interrupt. If my analysis > is not right, please correct me, thanks. > > Steps to reproduce (Have a certain probability): > 1. # vim /tmp/uncorrected > CPU 1 BANK 4 > STATUS uncorrected 0xc0 > MCGSTATUS EIPV MCIP > ADDR 0x1234 > RIP 0xdeadbabe > RAISINGCPU 0 > MCGCAP SER CMCI TES 0x6 > > 2. # modprobe mce_inject > 3. # cd /tmp > 4. # mce-inject uncorrected > Hi,
I tested the 5.9-rc5 version and found that the problem still exists. Is there a good solution ?
Best regards, Wu Bo
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