RFR 9: 7021006: (process) Remove disabled clone-exec feature

[Roger Riggs]

Hi Martin,

That part seems both dated and arcane;  it will be in the mercurial history
none the less.  I can't see how it could be applied unless we go back to 
clone.

Roger


On 3/27/2015 5:21 PM, Martin Buchholz wrote:
> Please also keep (most of?) the below.  The key piece of the history 
> is that glibc did not consider clone a public supported interface, 
> unlike vfork, but that might change.  This comment and the contents of 
> the glibc bug are an important part of Unix lore, although I'm hearing 
> you think there's a better place to record the arcane history of Unix...
>
> - * - clone() with flags CLONE_VM but not CLONE_THREAD.  clone() is
> - *   Linux-specific, but this ought to work - at least the glibc
> - *   sources contain code to handle different combinations of CLONE_VM
> - *   and CLONE_THREAD.  However, when this was implemented, it
> - *   appeared to fail on 32-bit i386 (but not 64-bit x86_64) Linux with
> - *   the simple program
> - *     Runtime.getRuntime().exec("/bin/true").waitFor();
> - *   with:
> - *     #  Internal Error (os_linux_x86.cpp:683), pid=19940, tid=2934639536
> - *     #  Error: pthread_getattr_np failed with errno = 3 (ESRCH)
> - *   We believe this is a glibc bug, reported here:
> - *http://sources.redhat.com/bugzilla/show_bug.cgi?id=10311
> - *   but the glibc maintainers closed it as WONTFIX.
> - *
>
>
> On Fri, Mar 27, 2015 at 2:14 PM, Roger Riggs <Roger.Riggs at oracle.com 
> <mailto:Roger.Riggs at oracle.com>> wrote:
>
>     Thanks Martin,
>
>     Updated the webrev in place to restore that context.
>
>     Roger
>
>
>
>     On 3/27/2015 5:00 PM, Martin Buchholz wrote:
>>     clone was never used in a released jdk.
>>
>>     I would leave the internal docs.  I left them in on purpose,
>>     because it was not at all obvious why we chose not to use clone.
>>
>>     I'm especially fond of
>>     - *   On Linux, one might think that vfork() would be implemented using
>>     - *   the clone system call with flag CLONE_VFORK, but in fact vfork is
>>     - *   a separate system call (which is a good sign, suggesting that
>>     - *   vfork will continue to be supported at least on Linux).
>>     Deleting the implementation using clone is a better idea; it's
>>     easy to resurrect in the unlikely case someone will want to.
>>
>>
>>     On Fri, Mar 27, 2015 at 1:50 PM, Roger Riggs
>>     <Roger.Riggs at oracle.com <mailto:Roger.Riggs at oracle.com>> wrote:
>>
>>         At one time clone() was used on Unix to spawn processes but
>>         no more.
>>         Please review the cleanup of now dead code.
>>
>>         Webrev:
>>         http://cr.openjdk.java.net/~rriggs//webrev-clone-7021006
>>         <http://cr.openjdk.java.net/%7Erriggs//webrev-clone-7021006>
>>
>>         Issue:
>>         https://bugs.openjdk.java.net/browse/JDK-7021006
>>
>>         Thanks, Roger
>>
>>
>
>