RFR: 8274986: max code printed in hs-err logs should be configurable [v2]

[Tom Rodriguez]

On Mon, 11 Oct 2021 08:30:48 GMT, Doug Simon <dnsimon at openjdk.org> wrote:

>> src/hotspot/share/code/codeBlob.cpp line 658:
>> 
>>> 656:     if (st == tty) {
>>> 657:       nm->print_nmethod(verbose);
>>> 658:     }
>> 
>> I think this should be something like this:
>> 
>>      ResourceMark rm;
>>      st->print(INTPTR_FORMAT " is at entry_point+%d in (nmethod*)" INTPTR_FORMAT,
>>                p2i(addr), (int)(addr - nm->entry_point()), p2i(nm));
>> -    if (verbose) {
>> -      st->print(" for ");
>> -      nm->method()->print_value_on(st);
>> -    }
>>      st->cr();
>> -    nm->print_nmethod(verbose);
>> +    if (verbose && st == tty) {
>> +      nm->print_nmethod(verbose);
>> +    } else {
>> +      nm->print_on(st);
>> +    }
>>      return;
>>    }
>>    st->print_cr(INTPTR_FORMAT " is at code_begin+%d in ", p2i(addr), (int)(addr - code_begin()));
>
> I don't think so. As far as I can see, the intent is to have a single line of output for an nmethod followed by an optional " for ..." suffix when `verbose == true`.
> The `nm->print_nmethod(verbose)` call then prints extra multi-line detail for the nmethod with the number of lines printed governed by `verbose`.
> This code seems like it went from being hard coded to always go to `tty` and was then parameterized to go to an arbitrary stream but the evolution accidentally overlooked some code that still goes to `tty`.
> I don't want to make extensive changes here as there really should be a single effort to rationalize all dumping to ensure it's parameterized.

I agree you might not want to bite this off in this PR, but this piece of code is reason you commonly see random nmethods appearing on the tty just before a crash.  verbose is only ever true when called from findpc in debug.cpp.  All the other non-verbose work print_nmethod does is useless, like writing to the xtty, and otherwise boils down to nm->print_on(tty).  But all these printing paths could use a rework so I'm fine if you skip it.

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PR: https://git.openjdk.java.net/jdk/pull/5875