RFR(M): 8141529: Fix handling of _JAVA_SR_SIGNUM

[Dmitry Samersoff]

Goetz,

*BSD including OS X also defines NSIG (just checked) and if my memory is
not bogus, AIX defines it too.

So you may consider to use NSIG on all platform.

-Dmitry

On 2015-11-12 11:36, Lindenmaier, Goetz wrote:
> OK I'll change it to NSIG.  That's used in other places in os_linux, too.
> So it's really more consistent.
> 
> Best regards,
>   Goetz
> 
>> -----Original Message-----
>> From: Dmitry Samersoff [mailto:dmitry.samersoff at oracle.com]
>> Sent: Donnerstag, 12. November 2015 09:22
>> To: David Holmes; Lindenmaier, Goetz; hotspot-runtime-
>> dev at openjdk.java.net; serviceability-dev
>> Subject: Re: RFR(M): 8141529: Fix handling of _JAVA_SR_SIGNUM
>>
>> David,
>>
>> I think it's better to use NSIG (without underscore) defined in signal.h
>>
>> -Dmitry
>>
>>
>> On 2015-11-12 10:35, David Holmes wrote:
>>> Hi Goetz,
>>>
>>> Adding in serviceability-dev
>>>
>>> On 9/11/2015 6:22 PM, Lindenmaier, Goetz wrote:
>>>> Hi,
>>>>
>>>> The environment variable _JAVA_SR_SIGNUM can be set to a signal
>> number
>>>> do be used by the JVM's suspend/resume mechanism.
>>>>
>>>> If set, a signal handler is installed and the current signal handler
>>>> is saved to an array.
>>>> On linux, this array had size MAXSIGNUM=32, and _JAVA_SR_SIGNUM
>> was
>>>> allowed
>>>> to range up to _NSIG=65. This could cause memory corruption.
>>>>
>>>> Further, in jsig.c, an unsinged int is used to set a bit for signals.
>>>> This also
>>>> is too small, as only 32 signals can be supported.  Further, the
>>>> signals are mapped
>>>> wrong to these bits.  '0' is not a valid signal, but '32' was.  1<<32
>>>> happens to map to
>>>> zero, so the signal could be stored, but this probably was not
>>>> intended that way.
>>>>
>>>> This change increases MAXSIGNUM to 65 on linux, and to 64 on aix. It
>>>> introduces
>>>> proper checking of the signal read from the env var, and issues a
>>>> warning if it
>>>> does not use the signal set.  It adapts the data types in jisig.c
>>>> properly.
>>>>
>>>> Please review this change.  I please need a sponsor.
>>>> http://cr.openjdk.java.net/~goetz/webrevs/8141529-NSIG/webrev.00
>>>
>>> This all sounds very good to me. (I must find out why Solaris is not
>>> involved here :) ).
>>>
>>> On Linux you didn't add the bounds check to os::Linux::set_our_sigflags.
>>>
>>> I'm also wondering about documenting where we are determining the
>>> maximum from? Is it simply _NSIG on some/all distributions? And I see
>>> _NSIG is supposed to be the biggest signal number + one. Also linux
>>> defines NSIG = _NSIG so which should we be using?
>>>
>>> Thanks,
>>> David
>>>
>>>> Best regards,
>>>>    Goetz.
>>>>
>>
>>
>> --
>> Dmitry Samersoff
>> Oracle Java development team, Saint Petersburg, Russia
>> * I would love to change the world, but they won't give me the sources.


-- 
Dmitry Samersoff
Oracle Java development team, Saint Petersburg, Russia
* I would love to change the world, but they won't give me the sources.