Thread panic is not handled

[zjp-CN]

arceos/modules/axruntime/src/lang_items.rs

Lines 3 to 7 in bcc354a

	#[panic_handler]
	fn panic(info: &PanicInfo) -> ! {
	error!("{}", info);
	axhal::power::system_off()
	}

ArceOS just powers off when a spanwed thread panics:

// axstd = { workspace = true, features = ["multitask"] }
#![no_std]
#![no_main]

use axstd::{println, thread};

#[unsafe(no_mangle)]
fn main() {
    _ = thread::spawn(|| panic!("thread spawned")).join();
    println!("main thread ends"); // This never runs.
}

[  0.014810 0:4 axruntime::lang_items:5] panicked at examples/helloworld/src/main.rs:8:26:
thread spawned

The panic shouldn't terminate main thread in ArceOS.

This playground link shows how libstd API behaves.

[AsakuraMizu]

Recovering from a panic is not an easy task; we may need to implement unwinding.

[zjp-CN]

Asterinas relies on unwinding crate to have unwinding.
Basically, the pattern is

1. for an operation that can panic, wrap it in catch_unwind to codegen a landing pad and a catch action
2. once a panic happens, the control flow jumps to the #[panic_handler]
3. begin_unwind called in the panic_handler automatically backtraces
4. when the stack frame lands at the catch point, the control flow jumps back to catch_unwind and continues as normal code

Some code for reference:

• kernel::thread::oops
• ostd::ktest::panic_handler
• ostd::panic module