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Add a workaround for a failing assertion

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In traceScanSegRes, the assertion

  AVER(RefSetSub(ScanStateUnfixedSummary(ss), SegSummary(seg)));

can fail if we call MPS_FIX1 on a reference but not MPS_FIX2.  In a
normal Emacs session that tends to happen after ~10 minutes.  If "write
barrier deferral" is disabled in config.h, then the tests in
mps/test/function/eph1.c will also run into this assertion.

I failed to create a reproducible test with write barrier deferral
enabled.  Obvioulsy, I don't understand this issue fully.

* mps/code/poolawl.c (aephFixKey): Include the key in the SegSummary.
(aephIsWhite): Return the new reference, so that we can avoid calling
MPS_FIX2 twice.
This commit is contained in:
Helmut Eller 2026-02-11 09:20:15 +01:00
parent 53fa8e0791
commit e34e1bc58d
1 changed files with 11 additions and 13 deletions
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24
mps/code/poolawl.c
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@ -1769,7 +1769,7 @@ mps_pool_class_t mps_class_aeph(void)
return (mps_pool_class_t)CLASS(AEPHPool);
}
static Res aephIsWhite(mps_ss_t mps_ss, mps_addr_t ref, Bool* isWhiteO)
static Res aephIsWhite(mps_ss_t mps_ss, mps_addr_t *refIO, Bool* isWhiteO)
{
ScanState ss = PARENT(ScanStateStruct, ss_s, mps_ss);
Rank savedRank = ss->rank;
@ -1780,11 +1780,11 @@ static Res aephIsWhite(mps_ss_t mps_ss, mps_addr_t ref, Bool* isWhiteO)
UNUSED(_mps_wt);
UNUSED(_mps_w);
UNUSED(_mps_zs);
res = MPS_FIX2(mps_ss, &ref);
res = MPS_FIX2(mps_ss, refIO);
}
MPS_SCAN_END(mps_ss);
ss->rank = savedRank;
*isWhiteO = (ref == NULL);
*isWhiteO = (*refIO == NULL);
return res;
}
@ -1823,23 +1823,20 @@ static Res aephFixKey(mps_ss_t mps_ss,
MPS_SCAN_BEGIN(mps_ss)
{
mps_addr_t key = *keyIO;
ScanState ss = PARENT(ScanStateStruct, ss_s, mps_ss);
Seg seg = aephSegOfAddr(ss->arena, base);
if (MPS_FIX1(mps_ss, key)) {
MPS_FIX_CALL(mps_ss, res = aephIsWhite(mps_ss, key, isKeyWhite));
SegSetSummary(seg, RefSetAdd(ss->arena, SegSummary(seg), key));
MPS_FIX_CALL(mps_ss, res = aephIsWhite(mps_ss, &key, isKeyWhite));
if (res != MPS_RES_OK)
return res;
if (*isKeyWhite) {
ScanState ss = PARENT(ScanStateStruct, ss_s, mps_ss);
Seg seg = aephSegOfAddr(ss->arena, base);
if (seg->propagationFinished) {
if (seg->propagationFinished)
*keyIO = NULL;
} else
else
aephDeferSeg(mps_ss, base, FALSE);
} else {
res = MPS_FIX2(mps_ss, &key);
if (res != MPS_RES_OK)
return res;
} else
*keyIO = key;
}
} else
*isKeyWhite = FALSE;
}
@ -1910,6 +1907,7 @@ mps_res_t mps_fix_weak_pair(mps_ss_t mps_ss,
if (res != MPS_RES_OK)
return res;
res = aephFixValue(mps_ss, isKeyWhite, base, valIO);
AVER(RefSetSub(ScanStateUnfixedSummary(ss), SegSummary(seg)));
return res;
}
case RankEXACT: {