== Why does my backtrace contain a mixture of function call chains? ==

So your kernel oopsed and gave you a stack trace that mostly makes sense, but has a function or two on it that do not get called at all in this code path?

This is a normal occurence in Linux. Unless `CONFIG_FRAME_POINTER` (or later, `CONFIG_UNWINDER_FRAME_POINTER` is enabled, the function `print_context_stack()` simply walks the whole stack and looks for any value that might be the address of a function in the kernel.  It has no way of knowing whether that address is a stack frame return address from the current code path, a left-over return address from a previous code path or just a random value that was left on the stack.

If you want to always get reliable stack traces when an oops happens, make sure you enable `CONFIG_FRAME_POINTER` or `CONFIG_UNWINDER_FRAME_POINTER`, as well as `CONFIG_STACKTRACE`, `CONFIG_UNWIND_INFO` and `CONFIG_STACK_UNWIND`. For x86_64, `CONFIG_UNWINDER_ORC` is also a reliable stack trace dumper.

With these configuration options switched on, the kernel knows exactly which addresses are part of the current call chain, and which are not.

== How do I manually get a stack trace? ==

You can manually try to create the stack trace from an oops message or from the stack dump of a task. See the [[http://kernelnewbies.org/ABI|ABI]] page for details on the stack convention for your architecture.

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[[CategoryFAQ]]