RFR (M): JDK-8200298 Unify all unix versions of libjsig/jsig.c

Magnus Ihse Bursie magnus.ihse.bursie at oracle.com
Thu Apr 5 08:07:23 UTC 2018



On 2018-04-04 09:59, David Holmes wrote:
> Hi Magnus,
>
> Sorry for the delay ...
>
> On 28/03/2018 8:15 PM, Magnus Ihse Bursie wrote:
>>
>> On 2018-03-27 18:24, Thomas Stüfe wrote:
>>> Hi Magnus,
>>>
>>> just a cursory look, will look in greater detail tomorrow.
>>>
>>> This is good, thanks for doing this.
>>>
>>> As I wrote offlist, please remove the painfully wrong AIX 
>>> "workarounds". I do not know why we did this - the original code is 
>>> quite old - my assumption is that dlsym(RTLD_NEXT) was not working 
>>> as expected on older AIX versions. Well, it should work now 
>>> according to IBMs manpages. Will test later.
>> Ok.
>>>
>>> __thread is not Posix. I would prefer pthread_get/set_specific 
>>> instead, which is more portable.
>>
>> I have surrounded this code with #ifdef MACOSX now.
>>
>> Here is an updated webrev. It includes the changes requested by you 
>> and David:
>>
>> * No more AIX workarounds
>> * Solaris use pthreads
>> * The "reentry" code is #ifdef MACOSX.
>
> That all seems good.
Good. :)

>
>> I also assumed that NSIG is available and working on Solaris. I'll 
>> let David decide if he is happy with that. The alternative is to go 
>> back to the Solaris-specific code that allocates sact on the heap.
>
> Unfortunately NSIG is a problem on Solaris:
>
> http://austingroupbugs.net/view.php?id=741
>
> It's use also precludes the use of the real-time signals - which 
> limits Linux as well. But I'm not completely clear on exactly how 
> signals may be numbered in their entirety so I wouldn't necessarily 
> suggest trying to use SIGRTMAX+1 as the number of available signals, 
> other than on Solaris.
Ok. I hope I understand you correctly. I have replaced NSIG with 
MAX_SIGNALS, which is defined as NSIG on all platforms except Solaris, 
where it is defined as SIGRTMAX+1.

Updated webrev:
http://cr.openjdk.java.net/~ihse/JDK-8200298-unify-libjsig/webrev.08

(8th time's a charm..?)

/Magnus

>
> Thanks,
> David
>
>> Webrev: 
>> http://cr.openjdk.java.net/~ihse/JDK-8200298-unify-libjsig/webrev.05
>>
>> Once again, here is also a webrev that shows the difference between 
>> the original files and the new, unified file. Even if it's hard to 
>> read, it shows what the effects will be for each platform.
>>
>> Webrev: 
>> http://cr.openjdk.java.net/~ihse/JDK-8200298-unify-libjsig/webrev.04/
>>
>> /Magnus
>>
>>>
>>> Thanks!
>>>
>>> Thomas
>>>
>>>
>>>
>>>
>>>
>>> On Tue, Mar 27, 2018 at 11:42 AM, Magnus Ihse Bursie 
>>> <magnus.ihse.bursie at oracle.com 
>>> <mailto:magnus.ihse.bursie at oracle.com>> wrote:
>>>
>>>     When I was about to update jsig.c, I noticed that the four copies
>>>     for aix, linux, macosx and solaris were basically the same, with
>>>     only small differences. Some of the differences were not even well
>>>     motivated, but were likely the result of this code duplication
>>>     causing the code to diverge.
>>>
>>>     A better solution is to unify them all into a single unix version,
>>>     with the few platform-specific changes handled on a per-platform
>>>     basis.
>>>
>>>     I've made the following notable changes:
>>>
>>>     * I have removed the version check for Solaris. All other
>>>     platforms seem to do fine without it, and in general, we don't
>>>     mistrust other JDK libraries. An alternative is to add this
>>>     version check to all other platforms instead. If you think this is
>>>     the correct course of action, let me know and I'll fix it.
>>>
>>>     * Solaris used to have a dynamically allocated sact, instead of a
>>>     statically allocated array as all other platforms have. It's not
>>>     likely to be large, and the size is known at compile time, so
>>>     there seems to be no good reason for this.
>>>
>>>     * Linux and macosx used a uint32_t/uint64_t instead of sigset_t
>>>     for jvmsigs, as aix and solaris do. This is a less robust
>>>     solution, and the added checks show that it has failed in the
>>>     past. Now all platforms use sigset_t/sigismember().
>>>
>>>     Also worth noting:
>>>
>>>     * Solaris is not using pthreads, but it's own thread library,
>>>     which accounts for most of the #ifdef SOLARIS.
>>>
>>>     * In general, if an implementation was needed on one platform, but
>>>     has no effect or is harmless on others, I've kept it on all
>>>     platforms instead of sprinkling the code with #ifdefs.
>>>
>>>     To facilitate code review, here is a specially crafted webrev that
>>>     shows the differences compared to each of the individual, original
>>>     per-OS versions of jsig.c:
>>> http://cr.openjdk.java.net/~ihse/JDK-8200298-unify-libjsig/webrev.01
>>> <http://cr.openjdk.java.net/%7Eihse/JDK-8200298-unify-libjsig/webrev.01>
>>>
>>>     Bug: https://bugs.openjdk.java.net/browse/JDK-8200298
>>>     <https://bugs.openjdk.java.net/browse/JDK-8200298>
>>>     WebRev:
>>> http://cr.openjdk.java.net/~ihse/JDK-8200298-unify-libjsig/webrev.03
>>> <http://cr.openjdk.java.net/%7Eihse/JDK-8200298-unify-libjsig/webrev.03>
>>>
>>>     /Magnus
>>>
>>>
>>



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