task tracer 信号追踪问题讨论

[CodeZHXS]

task tracer 目前有 ContextTrace 和 SignalTrace 两种回溯方式，SignalTrace 将信号发送给目标进程，目标进程处理信号的同时，将运行上下文 context 发送给 SignalTrace 的进程。

SignalHandler 函数启用了一个超时的时间（默认是 50ms），如果回溯超时，SignalHandler 会直接退出并结束。

这种方式会不会存在问题？例如，如果 SignalTrace 在 unw_init_local 之前，SignalHandler 就超时并退出了，这样的话 context 的内容难以保证不被修改，unw_init_local 可能会失败，或者存在 crash 的问题

[CodeZHXS]

@chenBright

[chenBright]

You are right. Because libunwind cannot fully guarantee asynchronous signal safety, the synchronization mechanism here is too complicated.

[CodeZHXS]

You are right. Because libunwind cannot fully guarantee asynchronous signal safety, the synchronization mechanism here is too complicated.

I am worried that in this case unw_init_local may crash due to accessing incorrect memory. Does this situation exist?

[chenBright]

Maybe. Regardless, this is unsafe and should be avoided.