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

Thomas Stüfe thomas.stuefe at gmail.com
Thu Mar 29 06:47:50 UTC 2018

On Thu, Mar 29, 2018 at 12:37 AM, Magnus Ihse Bursie < magnus.ihse.bursie at oracle.com> wrote:

On 2018-03-28 21:21, Thomas Stüfe wrote:

Hi Magnus, I had a closer look at the changes, especially at jsig.c. It all comes slowly back. The AIX version has been almost comically wrong. About NSIG, I remember that we had coding in our port which needed to know the max number of signals, and this was surprisingly hard since on some platforms. Sometimes NSIG does not contain the real time signals. Or it did not even exist. I think we ended up hardcoding an own max signal limit . So wherever you access sact with a signal number as index, I'd like to see a bounds check. Or at least an assert - since this is plain C, a C-assert would do for me (see http://pubs.opengroup.org/onlinepubs/009695399/ functions/assert.html). This also would guard against user parameter error. That's probably a good improvement. Do you think it could be handled as a follow-up bug? A simple bounds check would suffice for me. At the start of the external sigaction() and sigset(), just do a:

if (sig < 0 || sig >= NSIG) { return -1; }

In the external signal(), do a:

if (sig < 0 || sig >= NSIG) { return SIGERR; }

I also wonder whether this coding could not be simplified quite a bit by not calling the OS versions of signal() at all but instead doing all signal work via OS sigaction: after all, signal() can be implemented in terms of sigaction() (with the flag SASIGINFO cleared), and so can sigset(). This would remove the necessity of reentry-handling for macos, and also remove the need for savesignalhandler().

That also sounds like an excellent suggestion. Do you think it could be handled as a follow-up bug?

Sure!

I will test this version on AIX tomorrow. After that, I'll have some vacation, but maybe someone else from my team will take over. I like this work, this is a good simplification. Thanks. :) However, it's a bit outside what I normally do. :) Not that I dislike writing some good old C for a change, but I'm really trying to focus on cleaning up the flag handling in the build system. This was just a side-track when I was going to make a change in the jsig.c files (for adding JNIEXPORT) and realized it was four almost identical copies. I thought it would be trivial to unify them, and if it's trivial, it's better to do it yourself right away, than to file a bug on someone else, or so my motto goes. :) However, it turned out to be more work than I expected, and I'm losing interest in pushing this any further. Still, it would be a shame if the work I've done so far go to waste, but I'd really prefer it if someone else could pick up this patch and finish it. You are almost there. Lets finish this.

The source looks good to me, if you add above mentioned bounds checks. I'll build it on AIX later today (I just found out your 8200357 - which I need to build on AIX - does not apply to hs, and I need to switch to jdk/jdk. Sigh. The unification of hs/jdk cannot come too early.)

..Thomas

/Magnus

Thanks, Thomas

On Wed, Mar 28, 2018 at 12:15 PM, Magnus Ihse Bursie <_ _magnus.ihse.bursie at oracle.com> 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(RTLDNEXT) 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 pthreadget/setspecific 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. 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. 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> 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 uint32t/uint64t instead of sigsett 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 sigsett/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 Bug: https://bugs.openjdk.java.net/browse/JDK-8200298 WebRev: http://cr.openjdk.java.net/~ihse/JDK-8200298-unify-libjsig/w ebrev.03 /Magnus

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