RFR: 8324066: "clhsdb jstack" should not by default scan for j.u.c locks because it can be very slow [v3]

[Chris Plummer]

On Wed, 31 Jan 2024 03:50:29 GMT, Alex Menkov <amenkov at openjdk.org> wrote:

>> Chris Plummer has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   fix spacing
>
> test/hotspot/jtreg/serviceability/sa/ClhsdbJstackWithConcurrentLock.java line 65:
> 
>> 63:             for (String line : lines) {
>> 64:                 if (line.contains(key)) {
>> 65:                     String[] words = line.split(key + "|[, ]");
> 
> String.split() expect regexp as an argument
> Not sure how this code works (without escaping '$' and parentheses).
> I think it would be clearer to use standard regexp pattern/matcher, something like
> 
> 
> Pattern pattern = Pattern.compile("\\s+- <0x([0-9a-fA-F]+)>, \(a java/util/concurrent/locks/ReentrantLock\$NonfairSync\)");
> for (String line: lines) {
>     Matcher matcher = pattern.matcher(line);
>     if (matcher.find()) {
>         addressString = matcher.group(1);
>         break;
>     }
> }

I think `key` doesn't really matter when doing the split. `key` is mainly for finding the right line. The split is for tokenizing that line into words, and the only parts that matters for that are ' ' and the ',' being used as word delimiters. I think `key` should just be removed from the regex. I think the source of the bug is code copied from ClhsdbInspect.java:

                        // Escape the token "Method*=" because the split method uses
                        // a regex, not just a straight String.
                        String escapedKey = key.replace("*","\*");
                        String[] words = line.split(escapedKey+"|[ ]");

In this case key is `Method*=`. The code works and the escaping and searching for `key` is necessary because we are looking for something like `Method*=<0x00000000ffc2ed70>`, but I think this could have been simplified by including `=` in the split pattern rather than all of `escapedKey`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/17479#discussion_r1472293801