Author: stas Date: Tue Dec 7 09:52:06 2004 New Revision: 110120 URL: http://svn.apache.org/viewcvs?view=rev&rev=110120 Log: update the complicated story of signal handlers
Modified: perl/modperl/docs/trunk/src/docs/2.0/user/coding/coding.pod perl/modperl/docs/trunk/src/docs/2.0/user/troubleshooting/troubleshooting.pod Modified: perl/modperl/docs/trunk/src/docs/2.0/user/coding/coding.pod Url: http://svn.apache.org/viewcvs/perl/modperl/docs/trunk/src/docs/2.0/user/coding/coding.pod?view=diff&rev=110120&p1=perl/modperl/docs/trunk/src/docs/2.0/user/coding/coding.pod&r1=110119&p2=perl/modperl/docs/trunk/src/docs/2.0/user/coding/coding.pod&r2=110120 ============================================================================== --- perl/modperl/docs/trunk/src/docs/2.0/user/coding/coding.pod (original) +++ perl/modperl/docs/trunk/src/docs/2.0/user/coding/coding.pod Tue Dec 7 09:52:06 2004 @@ -464,6 +464,56 @@ modifying the computation logic to explicitly check for the timeout at intervals. +Talking about C<alarm()> under prefork mpm, POSIX signals seem to +work, but require Perl 5.8.x+. For example: + + use POSIX qw(SIGALRM); + my $mask = POSIX::SigSet->new( SIGALRM ); + my $action = POSIX::SigAction->new(sub { die "alarm" }, $mask); + my $oldaction = POSIX::SigAction->new(); + POSIX::sigaction(SIGALRM, $action, $oldaction ); + eval { + alarm 2; + sleep 10 # some real code should be here + alarm 0; + }; + POSIX::sigaction(SIGALRM, $oldaction); # restore original + warn "got alarm" if $@ and $@ =~ /alarm/; + +For more details see: +http://search.cpan.org/dist/perl/ext/POSIX/POSIX.pod#POSIX::SigAction. + +One could use the C<$SIG{ALRM}> technique, working for 5.6.x+, but it +works B<only> under DSO modperl build. Moreover starting from 5.8.0 +Perl delays signal delivery, making signals safe. This change may +break previously working code. For more information please see: +http://search.cpan.org/dist/perl/pod/perl58delta.pod#Safe_Signals and +http://search.cpan.org/dist/perl/pod/perlipc.pod#Deferred_Signals_%28Safe_Signals%29. + +For example if you had the alarm code: + + eval { + local $SIG{ALRM} = sub { die "alarm" }; + alarm 3; + sleep 10; # in reality some real code should be here + alarm 0; + }; + die "the operation was aborted" if $@ and $@ =~ /alarm/; + +It may not work anymore. Starting from 5.8.1 it's possible to +circumvent the safeness of signals, by setting: + + $ENV{PERL_SIGNALS} = "unsafe"; + +as soon as you start your program (e.g. in the case of mod_perl in +startup.pl). + +For more information please refer to: +http://search.cpan.org/dist/perl/pod/perl581delta.pod#Unsafe_signals_again_available +and http://search.cpan.org/dist/perl/pod/perlrun.pod#PERL_SIGNALS. + +Though if you use perl 5.8.x+ it's preferrable to use the POSIX +API technique explained earlier in this section. Modified: perl/modperl/docs/trunk/src/docs/2.0/user/troubleshooting/troubleshooting.pod Url: http://svn.apache.org/viewcvs/perl/modperl/docs/trunk/src/docs/2.0/user/troubleshooting/troubleshooting.pod?view=diff&rev=110120&p1=perl/modperl/docs/trunk/src/docs/2.0/user/troubleshooting/troubleshooting.pod&r1=110119&p2=perl/modperl/docs/trunk/src/docs/2.0/user/troubleshooting/troubleshooting.pod&r2=110120 ============================================================================== --- perl/modperl/docs/trunk/src/docs/2.0/user/troubleshooting/troubleshooting.pod (original) +++ perl/modperl/docs/trunk/src/docs/2.0/user/troubleshooting/troubleshooting.pod Tue Dec 7 09:52:06 2004 @@ -344,61 +344,10 @@ +=head2 Problems with Catching Signals -=head2 Problems with Catching Signals under Perl 5.8.x+ - -Starting from 5.8.0 Perl delays signal delivery, making signals -safe. This change may break previously working code. For more -information please see: -http://search.cpan.org/dist/perl/pod/perl58delta.pod#Safe_Signals and -http://search.cpan.org/dist/perl/pod/perlipc.pod#Deferred_Signals_%28Safe_Signals%29 - -For example if you had the alarm code: - - eval { - local $SIG{ALRM} = sub { die "alarm" }; - alarm 3; - sleep 10; # in reality some real code should be here - alarm 0; - }; - die "the operation was aborted" if $@ and $@ =~ /alarm/; - -It may not work anymore. Starting from 5.8.1 it's possible to -circumvent the safeness of signals, by setting: - - $ENV{PERL_SIGNALS} = "unsafe"; - -as soon as you start your program (e.g. in the case of mod_perl in -startup.pl). - -For more information please refer to: -http://search.cpan.org/dist/perl/pod/perl581delta.pod#Unsafe_signals_again_available -and http://search.cpan.org/dist/perl/pod/perlrun.pod#PERL_SIGNALS - -But most likely this is not what you want (since that circumvention -makes your code unsafe). The proper solution that works correctly -across all 5.8.x+ versions is to use the POSIX signal handling, which -bypasses perl signal mechanism. Our example should be rewritten as -follows: - - use POSIX qw(SIGALRM); - eval { - POSIX::sigaction(SIGALRM, - POSIX::SigAction->new(sub { die "alarm" })) - or die "Error setting SIGALRM handler: $!\n"; - alarm 3; - sleep 10; # in reality some real code should be here - alarm 0; - }; - die "the operation was aborted" if $@ and $@ =~ /alarm/; - -For more details see: -http://search.cpan.org/dist/perl/ext/POSIX/POSIX.pod#POSIX::SigAction - - - - - +See L<Using Signal +Handlers|docs::2.0::user::coding::coding/Using_Signal_Handlers>. --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
