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What is Rcu_sched self detected stall on CPU?
Cause. A ‘soft lockup’ is defined as a bug that causes the kernel to loop in kernel mode for more than 20 seconds, without giving other tasks a chance to run. The watchdog daemon will send an non maskable interrupt (NMI) to all CPUs in the system who in turn print the stack traces of their currently running tasks.
What is a CPU stall?
Stalled means the processor was not making forward progress with instructions, and usually happens because it is waiting on memory I/O. Understanding how much your CPUs are stalled can direct performance tuning efforts between reducing code or reducing memory I/O.
Are CPU spikes bad?
In all likelihood it shouldn’t be a real concern because your computer may be running background applications even though you don’t see them. If, however, the unexplained CPU spikes are significantly hindering your machine’s performance, you may need to troubleshoot and stop any harmful applications or processes.
What is a sequential lock?
The sequential lock, generally shortened to seq lock, is a newer type of lock introduced in the 2.6 kernel. It provides a simple mechanism for reading and writing shared data. It works by maintaining a sequence counter.
What does RCU _ SCHED detected stall on CPU 0 mean?
Under this condition, the device is not accessible via SSH or 3G. Kernel version is 3.2.54. “rcu_sched detected stall on CPU 0” is repeated many times, what does this indicate?
Why do I see errors in syslog but not a solution?
I see errors in syslog but I can’t find a solution. I tried changing kernel to older or newer versions but no difference. I moved everything to a new machine, but problem is still there. This has to be software related. Any idea ?
How to find the module responsible for the stall?
You need to find the module which is responsible for this bug — look at the processes stuck in D state when this happens, or use something like eBPF to trace new calls to module initialisation. Thanks for contributing an answer to Unix & Linux Stack Exchange!
How to fix server freeze with RCU _ SCHED?
Problem solved by disabling SMP (added “nosmp” parameter in Grub conf). The server is running fine now. In my case, I got this error suddently. There were 3 options that was helping me to boot (one at the time): Thanks for contributing an answer to Server Fault! Please be sure to answer the question. Provide details and share your research!