How to print the current thread stack trace inside

问题:

I would like to be able to print the stack trace of a thread in the Linux kernel.

In details: I want to add code to specific functions (e.g. swap_writepage() ) that will print the complete stack trace of the thread where this function is being called. Something like this:

int swap_writepage(struct page *page, struct writeback_control *wbc)
{

    /* code goes here to print stack trace */

    int ret = 0;

    if (try_to_free_swap(page)) {
        unlock_page(page);
        goto out;
    }
    if (frontswap_store(page) == 0) {
        set_page_writeback(page);
        unlock_page(page);
        end_page_writeback(page);
        goto out;
    }
    ret = __swap_writepage(page, wbc, end_swap_bio_write);
out:
    return ret;
}

My story: Recently, Linux kernel developers started to adopt object-oriented principles when improving the kernel, which is written in C. Since C is not an OO languages things started to look very ugly and harder ti understand, let alone not having a decent IDE that can analyze C code. And I do not want to get started on running Linux under a debugger. Note: if you are a kernel development newb and want to run Linux under a debugger do not put efforts into that...it will prove to be fruitless (stepping makes no sense).

回答1:

Linux kernel has very well known function called dump_stack() here, which prints the content of the stack. Place it in your function in according to see stack info.

回答2:

@rakib is exactly right of course.

In addition, I'd like to point out that one can define simple and elegant macros that help print debug info as and when required. Over the years, I've put these macros and conveneince routines into a header file; you can check it out and download it here: "A Header of Convenience".

There are macros / functions to:

• make debug prints along with funcname / line# info (via the usual printk() or trace_printk()) and only if DEBUG mode is On
• dump the kernel-mode stack
• print the current context (process or interrupt along with flags in the form that ftrace uses)
• a simple assert() macro (!)
• a cpu-intensive DELAY_LOOP (useful for test rigs that must spin on the processor)
• an equivalent to usermode sleep functionality
• a function to calculate the time delta given two timestamps (timeval structs)
• convert decimal to binary, and
• a few more.

Whew :-)