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Postings from February 2003
RE: [perl #20613] Perl_magic_setsig/clearsig problems (patch included)
From:
Anders Johnson
Date:
February 11, 2003 01:16
Subject:
RE: [perl #20613] Perl_magic_setsig/clearsig problems (patch included)
Message ID:
000e01c2d151$2228ca90$9800a8c0@wis.com
This thread seems to have died out unexpectedly. I've included my latest
patch (relative to 5.8.0), which is alleged to do the following:
+ Signal handler isn't freed until after the new disposition is
installed.
+ Signal can't get deferred and then polled after the handler is
removed.
+ delete $SIG{...} is roughly equivalent to $SIG{...}="DEFAULT".
+ A couple of redundant statements were removed.
There is still the issue of a signal handler calling die() while the
main thread is inside a destructor. I'd like to discuss what can be done
about this, but it shouldn't necessarily preclude applying the patch
as-is.
Robust, clean signal handling is apparently a goal of Perl 5.7.3 and
later. I think it's important to make that a reality, and not just a
promise. I'm here to help if I can.
Thanks,
&ers
----- Begin Patch -----
diff -Naur perl-5.8.0/mg.c perl-5.8.0-sig3/mg.c
--- perl-5.8.0/mg.c Sat Jun 15 13:16:44 2002
+++ perl-5.8.0-sig3/mg.c Wed Jan 29 17:17:46 2003
@@ -1028,6 +1028,14 @@
#endif
#ifndef PERL_MICRO
+#ifdef HAS_SIGPROCMASK
+static void
+restore_sigmask(pTHX_ SV *save_sv)
+{
+ sigset_t *ossetp = (sigset_t *) SvPV_nolen( save_sv );
+ (void)sigprocmask(SIG_SETMASK, ossetp, (sigset_t *)0);
+}
+#endif
int
Perl_magic_getsig(pTHX_ SV *sv, MAGIC *mg)
{
@@ -1061,19 +1069,67 @@
int
Perl_magic_clearsig(pTHX_ SV *sv, MAGIC *mg)
{
- I32 i;
+ /* XXX Some of this code was copied from Perl_magic_setsig. A
little
+ * refactoring might be in order.
+ */
+ register char *s;
STRLEN n_a;
- /* Are we clearing a signal entry? */
- i = whichsig(MgPV(mg,n_a));
- if (i) {
- if(PL_psig_ptr[i]) {
- SvREFCNT_dec(PL_psig_ptr[i]);
- PL_psig_ptr[i]=0;
- }
- if(PL_psig_name[i]) {
- SvREFCNT_dec(PL_psig_name[i]);
- PL_psig_name[i]=0;
- }
+ SV* to_dec;
+ s = MgPV(mg,n_a);
+ if (*s == '_') {
+ SV** svp;
+ if (strEQ(s,"__DIE__"))
+ svp = &PL_diehook;
+ else if (strEQ(s,"__WARN__"))
+ svp = &PL_warnhook;
+ else
+ Perl_croak(aTHX_ "No such hook: %s", s);
+ if (*svp) {
+ to_dec = *svp;
+ *svp = 0;
+ SvREFCNT_dec(to_dec);
+ }
+ }
+ else {
+ I32 i;
+ /* Are we clearing a signal entry? */
+ i = whichsig(s);
+ if (i) {
+#ifdef HAS_SIGPROCMASK
+ sigset_t set, save;
+ SV* save_sv;
+ /* Avoid having the signal arrive at a bad time, if
possible. */
+ sigemptyset(&set);
+ sigaddset(&set,i);
+ sigprocmask(SIG_BLOCK, &set, &save);
+ ENTER;
+ save_sv = newSVpv((char *)(&save), sizeof(sigset_t));
+ SAVEFREESV(save_sv);
+ SAVEDESTRUCTOR_X(restore_sigmask, save_sv);
+#endif
+ PERL_ASYNC_CHECK();
+#if defined(FAKE_PERSISTENT_SIGNAL_HANDLERS) ||
defined(FAKE_DEFAULT_SIGNAL_HANDLERS)
+ if (!sig_handlers_initted) Perl_csighandler_init();
+#endif
+#ifdef FAKE_DEFAULT_SIGNAL_HANDLERS
+ sig_defaulting[i] = 1;
+ (void)rsignal(i, &Perl_csighandler);
+#else
+ (void)rsignal(i, SIG_DFL);
+#endif
+ if(PL_psig_name[i]) {
+ SvREFCNT_dec(PL_psig_name[i]);
+ PL_psig_name[i]=0;
+ }
+ if(PL_psig_ptr[i]) {
+ to_dec=PL_psig_ptr[i];
+ PL_psig_ptr[i]=0;
+ LEAVE;
+ SvREFCNT_dec(to_dec);
+ }
+ else
+ LEAVE;
+ }
}
return 0;
}
@@ -1156,7 +1212,16 @@
register char *s;
I32 i;
SV** svp = 0;
+ /* Need to be careful with SvREFCNT_dec(), because that can have
side
+ * effects (due to closures). We must make sure that the new
disposition
+ * is in place before it is called.
+ */
+ SV* to_dec = 0;
STRLEN len;
+#ifdef HAS_SIGPROCMASK
+ sigset_t set, save;
+ SV* save_sv;
+#endif
s = MgPV(mg,len);
if (*s == '_') {
@@ -1168,7 +1233,7 @@
Perl_croak(aTHX_ "No such hook: %s", s);
i = 0;
if (*svp) {
- SvREFCNT_dec(*svp);
+ to_dec = *svp;
*svp = 0;
}
}
@@ -1179,6 +1244,17 @@
Perl_warner(aTHX_ packWARN(WARN_SIGNAL), "No such
signal: SIG%s", s);
return 0;
}
+#ifdef HAS_SIGPROCMASK
+ /* Avoid having the signal arrive at a bad time, if possible. */
+ sigemptyset(&set);
+ sigaddset(&set,i);
+ sigprocmask(SIG_BLOCK, &set, &save);
+ ENTER;
+ save_sv = newSVpv((char *)(&save), sizeof(sigset_t));
+ SAVEFREESV(save_sv);
+ SAVEDESTRUCTOR_X(restore_sigmask, save_sv);
+#endif
+ PERL_ASYNC_CHECK();
#if defined(FAKE_PERSISTENT_SIGNAL_HANDLERS) ||
defined(FAKE_DEFAULT_SIGNAL_HANDLERS)
if (!sig_handlers_initted) Perl_csighandler_init();
#endif
@@ -1186,20 +1262,26 @@
sig_ignoring[i] = 0;
#endif
#ifdef FAKE_DEFAULT_SIGNAL_HANDLERS
- sig_defaulting[i] = 0;
+ sig_defaulting[i] = 0;
#endif
SvREFCNT_dec(PL_psig_name[i]);
- SvREFCNT_dec(PL_psig_ptr[i]);
+ to_dec = PL_psig_ptr[i];
PL_psig_ptr[i] = SvREFCNT_inc(sv);
SvTEMP_off(sv); /* Make sure it doesn't go away on us */
PL_psig_name[i] = newSVpvn(s, len);
SvREADONLY_on(PL_psig_name[i]);
}
if (SvTYPE(sv) == SVt_PVGV || SvROK(sv)) {
- if (i)
+ if (i) {
(void)rsignal(i, &Perl_csighandler);
+#ifdef HAS_SIGPROCMASK
+ LEAVE;
+#endif
+ }
else
*svp = SvREFCNT_inc(sv);
+ if(to_dec)
+ SvREFCNT_dec(to_dec);
return 0;
}
s = SvPV_force(sv,len);
@@ -1211,8 +1293,7 @@
#else
(void)rsignal(i, SIG_IGN);
#endif
- } else
- *svp = 0;
+ }
}
else if (strEQ(s,"DEFAULT") || !*s) {
if (i)
@@ -1224,8 +1305,6 @@
#else
(void)rsignal(i, SIG_DFL);
#endif
- else
- *svp = 0;
}
else {
/*
@@ -1240,6 +1319,12 @@
else
*svp = SvREFCNT_inc(sv);
}
+#ifdef HAS_SIGPROCMASK
+ if(i)
+ LEAVE;
+#endif
+ if(to_dec)
+ SvREFCNT_dec(to_dec);
return 0;
}
#endif /* !PERL_MICRO */
diff -Naur perl-5.8.0/t/op/magic.t perl-5.8.0-sig3/t/op/magic.t
--- perl-5.8.0/t/op/magic.t Wed Jul 10 17:18:07 2002
+++ perl-5.8.0-sig3/t/op/magic.t Wed Jan 29 13:00:40 2003
@@ -36,7 +36,7 @@
return 1;
}
-print "1..46\n";
+print "1..48\n";
$Is_MSWin32 = $^O eq 'MSWin32';
$Is_NetWare = $^O eq 'NetWare';
@@ -67,7 +67,7 @@
close FOO; # just mention it, squelch used-only-once
if ($Is_MSWin32 || $Is_NetWare || $Is_Dos || $Is_MPE || $Is_MacOS) {
- skip('SIGINT not safe on this platform') for 1..2;
+ skip('SIGINT not safe on this platform') for 1..4;
}
else {
# the next tests are done in a subprocess because sh spits out a
@@ -98,7 +98,35 @@
close CMDPIPE;
- $test += 2;
+ open( CMDPIPE, "| $PERL");
+ print CMDPIPE <<'END';
+
+ { package X;
+ sub DESTROY {
+ kill "INT",$$;
+ }
+ }
+ sub x {
+ my $x=bless [], 'X';
+ return sub { $x };
+ }
+ $| = 1; # command buffering
+ $SIG{"INT"} = "ok5";
+ {
+ local $SIG{"INT"}=x();
+ print ""; # Needed to expose failure in 5.8.0 (why?)
+ }
+ sleep 1;
+ delete $SIG{"INT"};
+ kill "INT",$$; sleep 1;
+ sub ok5 {
+ print "ok 5\n";
+ }
+END
+ close CMDPIPE;
+ print $? & 0xFF ? "ok 6\n" : "not ok 6\n";
+
+ $test += 4;
}
# can we slice ENV?