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Name: perl-Sys-SigAction | Distribution: openSUSE Tumbleweed |
Version: 0.23 | Vendor: openSUSE |
Release: 1.28 | Build date: Sun Sep 11 08:07:16 2016 |
Group: Development/Libraries/Perl | Build host: reproducible |
Size: 37377 | Source RPM: perl-Sys-SigAction-0.23-1.28.src.rpm |
Packager: https://bugs.opensuse.org | |
Url: http://search.cpan.org/dist/Sys-SigAction/ | |
Summary: Perl extension for Consistent Signal Handling |
Prior to version 5.8.0 perl implemented 'unsafe' signal handling. The reason it is consider unsafe, is that there is a risk that a signal will arrive, and be handled while perl is changing internal data structures. This can result in all kinds of subtle and not so subtle problems. For this reason it has always been recommended that one do as little as possible in a signal handler, and only variables that already exist be manipulated. Perl 5.8.0 and later versions implements 'safe' signal handling on platforms which support the POSIX sigaction() function. This is accomplished by having perl note that a signal has arrived, but deferring the execution of the signal handler until such time as it is safe to do so. Unfortunately these changes can break some existing scripts, if they depended on a system routine being interrupted by the signal's arrival. The perl 5.8.0 implementation was modified further in version 5.8.2. From the perl 5.8.2 *perlvar* man page: The default delivery policy of signals changed in Perl 5.8.0 from immediate (also known as "unsafe") to deferred, also known as "safe signals". The implementation of this changed the 'sa_flags' with which the signal handler is installed by perl, and it causes some system routines (like connect()) to return EINTR, instead of another error when the signal arrives. The problem comes when the code that made the system call sees the EINTR code and decides it's going to call it again before returning. Perl doesn't do this but some libraries do, including for instance, the Oracle OCI library. Thus the 'deferred signal' approach (as implemented by default in perl 5.8 and later) results in some system calls being retried prior to the signal handler being called by perl. This breaks timeout logic for DBD-Oracle which works with earlier versions of perl. This can be particularly vexing, when, for instance, the host on which a database resides is not available: 'DBI->connect()' hangs for minutes before returning an error (and cannot even be interrupted with control-C, even when the intended timeout is only seconds). This is because SIGINT appears to be deferred as well. The result is that it is impossible to implement open timeouts with code that looks like this in perl 5.8.0 and later: eval { eval { local $SIG{ALRM} = sub { die "timeout" }; alarm 2; $sth = DBI->connect(...); alarm 0; }; alarm 0; die if $@; }; Or as the author of bug #50628 pointed out, might probably better be written as: eval { local $SIG{ALRM} = sub { die "timeout" }; eval { alarm 2; $sth = DBI->connect(...); alarm 0; }; alarm 0; die if $@; }; The solution, if your system has the POSIX sigaction() function, is to use perl's 'POSIX::sigaction()' to install the signal handler. With 'sigaction()', one gets control over both the signal mask, and the 'sa_flags' that are used to install the handler. Further, with perl 5.8.2 and later, a 'safe' switch is provided which can be used to ask for safe(r) signal handling. Using sigaction() ensures that the system call won't be resumed after it's interrupted, so long as die is called within the signal handler. This is no longer the case when one uses '$SIG{name}' to set signal handlers in perls >= 5.8.0. The usage of sigaction() is not well documented however, and in perl versions less than 5.8.0, it does not work at all. (But that's OK, because just setting '$SIG' does work in that case.) Using sigaction() requires approximately 4 or 5 lines of code where previously one only had to set a code reference into the %SIG hash. Unfortunately, at least with perl 5.8.0, the result is that doing this effectively reverts to the 'unsafe' signals behavior. It is not clear whether this would be the case in perl 5.8.2, since the safe flag can be used to ask for safe signal handling. I suspect this separates the logic which uses the 'sa_flags' to install the handler, and whether deferred signal handling is used. The reader should also note, that the behavior of the 'safe' attribute is not consistent with what this author expected. Specifically, it appears to disable signal masking. This can be examined further in the t/safe.t and the t/mask.t regression tests. Never-the-less, Sys::SigAction provides an easy mechanism for the user to recover the pre-5.8.0 behavior for signal handling, and the mask attribute clearly works. (see t/mask.t) If one is looking for specific safe signal handling behavior that is considered broken, and the breakage can be demonstrated, then a patch to t/safe.t would be most welcome. This module wraps up the POSIX:: routines and objects necessary to call sigaction() in a way that is as efficient from a coding perspective as just setting a localized '$SIG{SIGNAL}' with a code reference. Further, the user has control over the 'sa_flags' passed to sigaction(). By default, if no additional args are passed to sigaction(), then the signal handler will be called when a signal (such as SIGALRM) is delivered. Since sigaction() is not fully functional in perl versions less than 5.8, this module implements equivalent behavior using the standard '%SIG' array. The version checking and implementation of the 'right' code is handled by this module, so the user does not have to write perl version dependent code. The attrs hashref argument to set_sig_handler() is silently ignored, in perl versions less than 5.8. When this module was developed it was tested on perl 5.005 on solaris. That was in 2004. Now only perl versions >= 5.6 are supported. If you want this to work on perl 5.5 you will have comment out "use warnings" everywhere. It is hoped that with the use of this module, your signal handling behavior can be coded in a way that does not change from one perl version to the next, and that sigaction() will be easier for you to use.
Artistic-1.0 or GPL-1.0+
* Sun Sep 11 2016 coolo@suse.com - updated to 0.23 see /usr/share/doc/packages/perl-Sys-SigAction/Changes * Tue Jul 26 2016 coolo@suse.com - updated to 0.22 see /usr/share/doc/packages/perl-Sys-SigAction/Changes =head2 Changes in Sys::SigAction 0.22 20 Nov 2013 Fix lack of interpolation in Makefile.PL for unsupported MSWin OS. * Tue Nov 26 2013 coolo@suse.com - updated to 0.21 Remove erroneous note at the end of the POD related to references to this module in DBD:Oracle. In reality the reference was in DBI, and it is still there. Close pod error bug (which referred to the above paragraph) submitted by the Debian Packaging team. * Tue Aug 06 2013 coolo@suse.com - updated to 0.20 Even if C<Time::HiRes::ualarm()> exists, it may not necessarily work. (There were way too many broken smoke tests with were the result of this. One reason for this may bave been that the test was looking for too small an interval of sub-second timeouts. On busy systems, this may have been causing tests to fail. Got rid of the attempt at tracking broken environments in timeout.t (the hash structure mentioned in the previous change. The sub-second timer tests now set a timeout at 0.1 seconds, and check for a delta time the is less then 0.8 seconds. Proving that they completed in under 1 second, but give a wide range of execution time to account for busy systems. Also Makefile.PL now looks for C<Time::HiRes::ualarm()>, and tests it. If it works, high resolution timeouts are enabled in Sys Makefile.PL reports what it finds, and t/timeout.t reports when high resolution tests are disabled, but timeout.t should not fail because of this... it will just run fewer tests. =head2 Changes in Sys::SigAction 0.19 27 Jul 2013 Change sig_alarm() to use HiRes::ualarm() instead of HiRes::alarm(). Hoping to fix hires test failures on some platforms. Build a hash structure in timeout.t to disable the HiRes tests on certain platforms where these functions may to be consistently broken, but disable them for at least another round, hoping that the change to using HiRes::ualarm() solves the problem. Also, restructure timeout.t to hardcode the number of tests run. Apparently Test::More on perl 5.8.x insisteds on getting the plan before ANY tests are run. * Fri Jul 26 2013 coolo@suse.com - updated to 0.18 Fix "bareword" error on some platforms at least, by explicitly importing INT_MAX from POSIX module. Fix Changes file which listed verson 0.16 twice when it should have list version 0.17 for the more recent changes. =head2 Changes in Sys::SigAction 0.17 22 Jul 2013 Fix timeout.t to use POSIX::pause() instead of select(), which was used to optimized the while ( 1 ) loop in the forever function. This caused failures on some platforms. pause() is right solution -- thanks (again) to Carsten Gaebler and for the suggestion for handling the Time::HiRes request. More double eval documentation cleanup that had not been previously caught in the POD. (bug #79130). When Time::HiRes is present, allow for long timeouts longer than the POSIX::MAX_INT microseconds when Time::HiRes is present. Just call call alarm() instead of ualarm() in the case where input argument would result in a msecs value in an argument to ualarm which is larger than POSIX::INT_MAX (and, of course, add a test for this in timeout.t). (bug/enhancement request #75784) Fix typos in dbd-oracle-timeout.POD (bug #87141). It appears that the DBD:oracle module may now have internal handling for this problem (DBD::oracle not longer references Sys::SigAction). =head2 Changes in Sys::SigAction 0.16 21 Jul 2013 Thanks to excellent patches from Carsten Gaebler (contact me if you want to contact him), timeout_call() now supports passing an array of arguments which it will pass to the code it executes. Minor tweak to POD. * Tue Nov 27 2012 crrodriguez@opensuse.org - skip test suite when building in qemu arm emulator * Sun Jan 01 2012 coolo@suse.com - update to 0.15 No functional changes. Fix for test timeout.t. Fix strict undefined symbol error in timeout.t, when Time::HiRes is not present. Not sure if constant pragma will exist in all supported perl versions, so, we just commented out the use strict in this test * Wed Dec 01 2010 coolo@novell.com - switch to perl_requires macro * Sat Jul 25 2009 chris@computersalat.de - spec mods * removed ^---------- * removed ^#--------- * Wed Jul 01 2009 chris@computersalat.de - update to 0.11 - added perl-macros o autogen filelist with perl_gen_filelist
/usr/lib/perl5/vendor_perl/5.40.0/Sys /usr/lib/perl5/vendor_perl/5.40.0/Sys/SigAction /usr/lib/perl5/vendor_perl/5.40.0/Sys/SigAction.pm /usr/lib/perl5/vendor_perl/5.40.0/Sys/SigAction/Alarm.pm /usr/share/doc/packages/perl-Sys-SigAction /usr/share/doc/packages/perl-Sys-SigAction/Changes /usr/share/doc/packages/perl-Sys-SigAction/README /usr/share/man/man3/Sys::SigAction.3pm.gz
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Fabrice Bellet, Wed Sep 11 23:45:42 2024