RFR: 8324668: JDWP process management needs more efficient file descriptor handling [v6]

[David Holmes]

On Wed, 31 Jan 2024 01:46:57 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:
> 
>   Chris' review suggestion - replace LOG_MISC with ERROR_MESSAGE

A couple of minor nits to fix before integrating but otherwise looks good. Thanks again for taking this on.

src/jdk.jdwp.agent/unix/native/libjdwp/exec_md.c line 35:

> 33: #include "sys.h"
> 34: #include "util.h"
> 35: #include "error_messages.h"

Nit: to maintain include sort order this should have gone where `log_messages.h` was removed.

src/jdk.jdwp.agent/unix/native/libjdwp/exec_md.c line 100:

> 98:     if ((dp = opendir(FD_DIR)) == NULL) {
> 99:         ERROR_MESSAGE(("failed to open dir %s while determining"
> 100:                   " file descriptors to close for process %d", FD_DIR, getpid()));

Nit: indent of second line is now off - please align "

src/jdk.jdwp.agent/unix/native/libjdwp/exec_md.c line 139:

> 137:         ERROR_MESSAGE(("failed to close file descriptors of"
> 138:                   " child process optimally, falling back to closing"
> 139:                   " %d file descriptors sequentially", (max_fd - i + 1)));

Nit: please realign lines on "

-------------

Marked as reviewed by dholmes (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/17588#pullrequestreview-1852976350
PR Review Comment: https://git.openjdk.org/jdk/pull/17588#discussion_r1472358835
PR Review Comment: https://git.openjdk.org/jdk/pull/17588#discussion_r1472359191
PR Review Comment: https://git.openjdk.org/jdk/pull/17588#discussion_r1472359972