RFR[9u-dev]: 8151442: jstack doesn't close quotation marks properly with threads' name greater than 1996 characters

[Cheleswer Sahu]

Thanks Dmitry for review. I will file CR and let you know once done.


Cheleswer


-----Original Message-----
From: Dmitry Samersoff 
Sent: Friday, March 18, 2016 2:35 PM
To: Cheleswer Sahu; hotspot-runtime-dev at openjdk.java.net; serviceability-dev at openjdk.java.net
Subject: Re: RFR[9u-dev]: 8151442: jstack doesn't close quotation marks properly with threads' name greater than 1996 characters

Cheleswer,

Fix (as immediate solution) looks good for me.

But IMHO, silent truncation of the output inside output stream is not a correct behavior. So please file a follow-up CR to have it addressed.

-Dmitry

On 2016-03-18 10:54, Cheleswer Sahu wrote:
> Hi,
> 
>  
> 
> Please review the code changes for https://bugs.openjdk.java.net/browse/JDK-8151442.
> 
>  
> 
> Webrev Link: http://cr.openjdk.java.net/~csahu/8151442/
> 
>  
> 
> Bug Brief: 
> 
> In jstack thread dumps , thread name greater than 1996 characters doesn't close quotation marks properly. 
> 
>  
> 
> Problem Identified:
> 
> Jstack is using below code to print thread name
> 
>  
> 
> src/share/vm/runtime/thread.cpp
> 
> void JavaThread::print_on(outputStream *st) const {
> 
>   st->print("\"%s\" ", get_thread_name());
> 
>  
> 
> Here "st->print()"  internally uses max buffer length as O_BUFLEN (2000).
> 
>  
> 
> void outputStream::do_vsnprintf_and_write_with_automatic_buffer(const char* format, va_list ap, bool add_cr) {
>   char buffer[O_BUFLEN];
> 
>  
> 
>  
> 
> do_vsnprintf_and_write_with_automatic_buffer() finally calls  
> "vsnprintf()"  which truncates the anything greater than the max 
> size(2000). In this case thread's name(> 1996) along with quotation 
> marks (2)
> 
> plus one terminating character exceeds the  max buffer size (2000), therefore the closing quotation  marks gets truncated.
> 
>  
> 
>  
> 
> Solution:
> 
> Split the  "st->print("\"%s\" ", get_thread_name())" in two statements
> 
> 1.       st->print("\"%s", get_thread_name());
> 
> 2.       st->print("\" ");
> 
>  
> 
> This will ensure presence of closing quotation mark always.
> 
>  
> 
>  
> 
> Regards,
> 
> Cheleswer
> 
>  
> 
>  
> 
>  
> 


--
Dmitry Samersoff
Oracle Java development team, Saint Petersburg, Russia
* I would love to change the world, but they won't give me the sources.