RFR(M): 8141529: Fix handling of _JAVA_SR_SIGNUM (original) (raw)

Lindenmaier, Goetz goetz.lindenmaier at sap.com
Thu Nov 12 08:22:34 UTC 2015

Hi David,

thanks for looking at this!

-----Original Message----- From: David Holmes [mailto:david.holmes at oracle.com] Sent: Donnerstag, 12. November 2015 08:35 To: Lindenmaier, Goetz; hotspot-runtime-dev at openjdk.java.net; serviceability-dev Subject: Re: RFR(M): 8141529: Fix handling of JAVASRSIGNUM

Hi Goetz, Adding in serviceability-dev On 9/11/2015 6:22 PM, Lindenmaier, Goetz wrote: > Hi, > > The environment variable JAVASRSIGNUM 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 JAVASRSIGNUM 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 :) ). The mechanism is not implemented there. Why, I don't know.

On Linux you didn't add the bounds check to os::Linux::setoursigflags. It came with 8140482 http://hg.openjdk.java.net/jdk9/hs-rt/hotspot/rev/cd86b5699825

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? I checked a row of linux distributions and Versions and always found NSIG=65. Also, as we compile NSIG into the code, we can not react on a difference between systems. So I guess that's fine. As NSIG = _NSIG, I don't really care which we use. I chose _NSIG because it was used before. On the other platforms I only found NSIG in the header files.

Best regards, Goetz

Thanks, David > Best regards, > Goetz. >

More information about the hotspot-runtime-dev mailing list