RFR: 8374862: assert(false) failed: Attempting to acquire lock MDOExtraData_lock/nosafepoint-1 out of order with lock tty_lock/tty -- possible deadlock (running with -XX:+Verbose -XX:+WizardMode -XX:+PrintDeoptimizationDetails) [v6]

[Guanqiang Han]

On Thu, 15 Jan 2026 06:49:55 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Guanqiang Han has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   fix a compile error
>
> src/hotspot/share/utilities/ostream.hpp line 162:
> 
>> 160:    virtual ~outputStream() {}   // close properly on deletion
>> 161:    // Return true if this stream buffers/accumulates output in memory (e.g., stringStream)
>> 162:    virtual bool is_buffered() const { return false; }
> 
> Really you are using this as a proxy for "do I have a stringStream?" and it doesn't quite work because we also have a `bufferedStream` class that you have not marked as buffered - though I'm not sure the "buffering" in the two cases is actually the same thing.
> 
> @dean-long you made this suggestion so how do you see `is_buffered` fitting in to the whole stream hierarchy?

I agree with the concern here. The buffering we need is local to this call site to keep the output coherent (collect everything and print once).
Whether we need to buffer/accumulate output for coherence is scenario-dependent, rather than a property that should permanently classify a stream type as “buffered” vs. “unbuffered”.
@dean-long what’s your view on this?

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PR Review Comment: https://git.openjdk.org/jdk/pull/29186#discussion_r2693255744