[PATCH] 8170639: [Linux] jsig is limited to a maximum of 64 signals

[Ao Qi]

Hi,

On Tue, Dec 18, 2018 at 4:32 AM David Holmes <david.holmes at oracle.com> wrote:
>
> On 17/12/2018 9:48 pm, Ao Qi wrote:
> > Hi David Holmes,
> >
> > Thanks for your reply. It makes sense. Is it possible to create
> > another bug ID to fix the problem?
>
> I'd prefer to see this fixed properly than point fixed on linux for an
> unsupported platform.

I thought the problem is "[Linux] jsig is limited to a maximum of 64
signals" and the patch was intended to fixed this problem. It just
didn't use "A better solution", but I think it is better than the
current situation.

Is zero/mips (or all platforms having more than 64 signals) a
unsupported platform?

Cheers,
Ao Qi
>
> Thanks,
> David
>
> > Cheers,
> > Ao Qi
> >
> > On Mon, Dec 17, 2018 at 7:30 PM David Holmes <david.holmes at oracle.com> wrote:
> >>
> >> Thanks for reminding me about the rest of the discussion. The point of
> >> the RFE I filed was to examine if we could get a consolidated POSIX
> >> version using sigset_t. I'd rather see that than a point fix for Linux.
> >>
> >> Thanks,
> >> David
> >>
> >> On 17/12/2018 6:50 pm, Ao Qi wrote:
> >>> Hi David Holmes,
> >>>
> >>> I am not sure what is the specific issue of "NSIG not being defined".
> >>> Do you mean the issue mentioned in "but I found that NSIG was missing
> >>> from signal.h on some architectures, mips being among them"[1]? If
> >>> yes, James Cowgill answered this in [2]. I check it on MIPS, NSIG is
> >>> defined in signal.h and it is 128.
> >>>
> >>> Cheers,
> >>> Ao Qi
> >>>
> >>> [1] http://mail.openjdk.java.net/pipermail/hotspot-dev/2016-November/025401.html
> >>> [2] http://mail.openjdk.java.net/pipermail/hotspot-dev/2016-December/025416.html
> >>>
> >>> On Mon, Dec 17, 2018 at 8:02 AM David Holmes <david.holmes at oracle.com> wrote:
> >>>>
> >>>> Hi,
> >>>>
> >>>> Was the issue of NSIG not being defined resolved?
> >>>>
> >>>> Thanks,
> >>>> David
> >>>>
> >>>> On 14/12/2018 10:23 pm, Ao Qi wrote:
> >>>>> Hi all,
> >>>>>
> >>>>> Zero does not build on Linux MIPS (actually all Linux of NSIG > 64)
> >>>>> since OpenJDK 9, because NISG is 128 on MIPS and can not be encoded in
> >>>>> uint64_t sigs. James Cowgill from Debian tried to push a patch fixing
> >>>>> this[1] but it seems he failed. I would like to try again to request
> >>>>> fixing this in http://hg.openjdk.java.net/jdk/jdk. This was fixed in
> >>>>> AIX implementation.
> >>>>>
> >>>>> After applying this patch, zero can be built on MIPS (Debian testing).
> >>>>> I've run the jtreg tests [2] on x86 Linux.
> >>>>>
> >>>>> [1] http://mail.openjdk.java.net/pipermail/hotspot-dev/2016-November/025399.html
> >>>>> [2] https://download.java.net/openjdk/testresults/12/docs/howtoruntests.html
> >>>>>
> >>>>> Cheers,
> >>>>> Ao Qi
> >>>>>
> >>>>> $ hg export -r 52869
> >>>>> # HG changeset patch
> >>>>> # User aoqi
> >>>>> # Date 1544089853 0
> >>>>> #      Thu Dec 06 09:50:53 2018 +0000
> >>>>> # Node ID 3eea22b79dc3a4bf26616bde1acb587e3f56e6fe
> >>>>> # Parent  b4982a22926b4ddf1a7b1f770e4d42ce8c1dd575
> >>>>> 8170639: [Linux] jsig is limited to a maximum of 64 signals
> >>>>>
> >>>>> diff -r b4982a22926b -r 3eea22b79dc3 src/hotspot/os/linux/os_linux.cpp
> >>>>> --- a/src/hotspot/os/linux/os_linux.cpp Thu Dec 06 11:54:39 2018 +0530
> >>>>> +++ b/src/hotspot/os/linux/os_linux.cpp Thu Dec 06 09:50:53 2018 +0000
> >>>>> @@ -4434,10 +4434,7 @@
> >>>>>
> >>>>>     // For signal-chaining
> >>>>>     struct sigaction sigact[NSIG];
> >>>>> -uint64_t sigs = 0;
> >>>>> -#if (64 < NSIG-1)
> >>>>> -#error "Not all signals can be encoded in sigs. Adapt its type!"
> >>>>> -#endif
> >>>>> +sigset_t sigs;
> >>>>>     bool os::Linux::libjsig_is_loaded = false;
> >>>>>     typedef struct sigaction *(*get_signal_t)(int);
> >>>>>     get_signal_t os::Linux::get_signal_action = NULL;
> >>>>> @@ -4516,7 +4513,7 @@
> >>>>>     }
> >>>>>
> >>>>>     struct sigaction* os::Linux::get_preinstalled_handler(int sig) {
> >>>>> -  if ((((uint64_t)1 << (sig-1)) & sigs) != 0) {
> >>>>> +  if (sigismember(&sigs, sig)) {
> >>>>>         return &sigact[sig];
> >>>>>       }
> >>>>>       return NULL;
> >>>>> @@ -4525,7 +4522,7 @@
> >>>>>     void os::Linux::save_preinstalled_handler(int sig, struct sigaction& oldAct) {
> >>>>>       assert(sig > 0 && sig < NSIG, "vm signal out of expected range");
> >>>>>       sigact[sig] = oldAct;
> >>>>> -  sigs |= (uint64_t)1 << (sig-1);
> >>>>> +  sigaddset(&sigs, sig);
> >>>>>     }
> >>>>>
> >>>>>     // for diagnostic
> >>>>> @@ -4616,6 +4613,7 @@
> >>>>>           (*begin_signal_setting)();
> >>>>>         }
> >>>>>
> >>>>> +    ::sigemptyset(&sigs);
> >>>>>         set_signal_handler(SIGSEGV, true);
> >>>>>         set_signal_handler(SIGPIPE, true);
> >>>>>         set_signal_handler(SIGBUS, true);
> >>>>>