RFR: 8324668: JDWP process management needs more efficient file descriptor handling [v2]

[Gerard Ziemski]

On Fri, 26 Jan 2024 15:57:57 GMT, Jaikiran Pai <jpai at openjdk.org> wrote:

>> Can I please get a review of this change which proposes to address https://bugs.openjdk.org/browse/JDK-8324668?
>> 
>> This change proposes to fix the issue in jdwp where when launching a child process (for the `launch=<cmd>` option), it iterates over an extremely large number of file descriptors to close each one of those. Details about the issue and the proposed fixed are added in a subsequent comment in this PR https://github.com/openjdk/jdk/pull/17588#issuecomment-1912256075. tier1, tier2 and tier3 testing is currently in progress with this change.
>
> Jaikiran Pai has updated the pull request incrementally with one additional commit since the last revision:
> 
>   use the right include for rlim_t - <sys/resource.h>

src/jdk.jdwp.agent/unix/native/libjdwp/exec_md.c line 112:

> 110:     }
> 111: 
> 112:     closedir(dp);

Should this be:

`    (void)closedir(dp);`

to show that we're ignoring the return value?

Since this area is pretty mysterious to deal with, should we consider checking whether `closedir()` actually returns am error, and at least be verbal and print a warning, as opposed to silently ignoring it?

Printing a warning, might help us diagnose any issue in the future?

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PR Review Comment: https://git.openjdk.org/jdk/pull/17588#discussion_r1467934723