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Postings from October 2003
On Wed, Oct 22, 2003 at 10:15:52PM +0200, Elizabeth Mattijsen wrote:
> Well, maybe someone can figure out what is going on here and maybe
> we'll get a fix for 5.8.2?
Fixed in bleedperl by change #21527
The leak could be reduced to
my @a : shared;
$a[0] = &share([]) while 1;
Whether this will be integrated in 5.8.2 is up to Nick.
The gory details:
While in shared interpeter context, the call to sv_setsv() that updates
the (shared interpreter) RV at $a[0] to refer to the new (shared
interpreter) [] also causes the old thing the RV was pointing to to be
freed. But a cunning bit of code in sv_unref_flags() doesn't free the old
referent immediately; instead it is converted into a mortal, and so freed
later. This is apparently to handle stuff like $a = $a->[0]. However, this
means that the mortal was added to the tmps stack of the *shared
interpreter*, which never gets freed. Adding a SAVETMPS/FREETMPS within
the shared context block of code solved the problem.
--
You never really learn to swear until you learn to drive.
Change 21527 by davem@davem-percy on 2003/10/23 19:13:20
Fix two threads::shared leaks
#24061 - AV in shared interpreter wasn't set to AvREAL
#24255 - mortals were added to the shared interpreter's tmpstack
and never freed.
Affected files ...
... //depot/perl/ext/threads/shared/shared.xs#38 edit
Differences ...
==== //depot/perl/ext/threads/shared/shared.xs#38 (text) ====
@@ -308,6 +308,8 @@
if (sv && SvTYPE(ssv) < SvTYPE(sv)) {
SHARED_CONTEXT;
sv_upgrade(ssv, SvTYPE(*psv));
+ if (SvTYPE(ssv) == SVt_PVAV) /* #24061 */
+ AvREAL_on(ssv);
CALLER_CONTEXT;
}
@@ -436,6 +438,12 @@
if (target) {
SV *tmp;
SHARED_CONTEXT;
+ /* #24255: sv_setsv() (via sv_unref_flags()) may cause a
+ * deferred free with sv_2mortal(). Ensure that the free_tmps
+ * is done within this inpterpreter. DAPM.
+ */
+ ENTER;
+ SAVETMPS;
tmp = newRV(SHAREDSvPTR(target));
sv_setsv_nomg(SHAREDSvPTR(shared), tmp);
SvREFCNT_dec(tmp);
@@ -444,6 +452,8 @@
SvOBJECT_on(SHAREDSvPTR(target));
SvSTASH(SHAREDSvPTR(target)) = (HV*)fake_stash;
}
+ FREETMPS;
+ LEAVE;
CALLER_CONTEXT;
}
else {