On Fri, Aug 04, 2017 at 11:58:51AM -0700, Kaz Kylheku wrote: > On 04.08.2017 10:02, Corinna Vinschen wrote: > >On Aug 4 00:44, Noah Misch wrote: > >>The attached demonstration program blocks signals (with sigprocmask()) > >>to > >>achieve mutual exclusion between signal handlers. It aborts upon > >>receipt of a > >>blocked signal. On "CYGWIN_NT-10.0 2.7.0(0.306/5/3) 2017-02-12 13:18 > >>x86_64", > >>signals regularly arrive despite being blocked. Essential parts of the > >>program include handling two signal numbers and having handlers run for > >>at > >>least 1-2ms; this problem goes away if I remove one of those > >>attributes. > >>GNU/Linux, AIX, Solaris, and "CYGWIN_NT-6.0 1.7.27(0.271/5/3) > >>2013-12-09 11:57 > >>i686" never deliver a blocked signal to this program. I think this > >>Cygwin > >>behavior is non-conforming. > > > >Thanks for the testcase. I debugged this a while today but the problem > >is far from trivial, apparently. Don't hold your breath for a quick > >solution.
Understood. Thanks for studying it. > The test case depends on accesses to the global variable sigblocked not > to be reordered w.r.t. siggprocmask calls. > > It is important that the variable not be set to 1 until after the signals > are > blocked, and be reset to 0 until after they are unblocked. > > Thus, the variable should be declared volatile. Agreed, but ... > Although I would be surprised if this were actually happening ... indeed, that didn't change the result. > Also, related remarks: for the reason that we can't factor out compiler > behavior, with absolute certainty, it would be good to mention not only > the system versions but also GCC. The compiler differs, obviously, > between Cygwin 1.7 and 2.7; not to mention that the case is reported > against i686 of the one, and x86_74 of the other. The Cygwin 2.7 system has gcc-core 5.4.0-1. The unaffected Cygwin 1.7 system has gcc-core 4.8.2-2. -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
