* Arjan van de Ven <[EMAIL PROTECTED]> wrote:
> During the work on the x86 32 and 64 bit backtrace code I found it
> useful to have a simple test module to test a process and irq context
> backtrace. Since the existing backtrace code was buggy, I figure it
> might be useful to have such a test module in the kernel so that maybe
> we can even detect such bugs earlier..
cool patch, applied!
a few suggestions:
a fundamental one: could you do a save_stack_trace() and check that both
the process context and the irq context functions are present in that
trace? If not then flag it as a regression and emit a real WARN_ON()
warning.
i.e. use save_stack_trace() to do a "silent" test - instead of emitting
backtraces during bootup. (which are marked via 'this is not a bug' but
which are visually active nevertheless.)
the locking selftests use similar techniques to never emit real
warnings, just a readable table of test results:
| Locking API testsuite:
----------------------------------------------------------------------------
| spin |wlock |rlock |mutex | wsem | rsem |
--------------------------------------------------------------------------
A-A deadlock: ok | ok | ok | ok | ok | ok |
A-B-B-A deadlock: ok | ok | ok | ok | ok | ok |
internally, while the test is running, lockdep is triggered for real but
the debug output and the backtraces are supressed.
and a few small details:
> + printk("====[ backtrace testing ]===========\n");
> + printk("Testing a backtrace from process context.\n");
> + printk("The following trace is a kernel self test and not a bug!\n");
the printks need a KERN_ attribute.
> + dump_stack();
> +
> + init_timer(&backtrace_timer);
> + backtrace_timer.function = backtrace_test_timer;
> + mod_timer(&backtrace_timer, jiffies + 10);
> +
> + msleep(10);
> + printk("====[ end of backtrace testing ]====\n");
would be nice to have a testcase for the NMI watchdog and the softlockup
watchdog as well: do they properly detect lockups on all CPUs?
> +static void exitf(void)
s/exitf/exit_backtrace_test
> + This option provides a kernel module that can be used to test
> + the kernel stack backtrace code. This option is not useful
> + for distributions or general kernels, but only for kernel
> + developers working on architecture code.
s/but only/only
Ingo
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