732845 - IonMonkey: Assertion failure: mutationCount == p.mutationCount, at ./dist/include/js/HashTable.h:688

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Christian Holler (:decoder)]

Attachment: Testcase for shell

The attached testcase asserts on ionmonkey revision 1fd6c40d3852 (run with --ion -n -m --ion-eager), tested on 64 bit.

Comment 1

[Gary Kwong [:gkw] [:nth10sd] (NOT official MoCo now)]

See bug 738496 comment 2 for a reliably small testcase with the same assertion on IonMonkey.

Comment 2

[Christian Holler (:decoder)]

Not sure if the test here is still valid, marking for a check. But even if it is not, we should ensure that the cause is the same as e.g. in bug 738496 because it seems like a generic assertion to me that multiple memory corruptions could produce.

Comment 3

[Christian Holler (:decoder)]

JSBugMon: The testcase found in this bug no longer reproduces (tried revision fe58c6671ebd).

Comment 4

[Christian Holler (:decoder)]

This is very likely a memory corruption, marking s-s until resolved.

Comment 5

[Christian Holler (:decoder)]

Bisect points to a merge here, unlikely that it fixed this issue. Someone needs to investigate this on the original revision.

Comment 6

[Christian Holler (:decoder)]

Note that I still see this assertion in the fuzzer, but the tests are always very complex and hard to reduce. If this assertion is very generic, then we can compose a new test to analyze to ensure that we're working on the correct issue.

Comment 8

[Jan de Mooij [:jandem]]

Attachment: Fix

The bug is that in generateVMWrapper we do this:
--
VMWrapperMap::AddPtr p = functionWrappers_->lookupForAdd(&f);
if (p)
    return p->value;
// ...
IonCode *wrapper = linker.newCode(cx);
if (!wrapper || !functionWrappers_->add(p, &f, wrapper))
    return NULL;
---
This is only safe if functionWrappers_ is not modified between the |lookupForAdd| and |add| calls. However, linker.newCode may trigger a last ditch GC and sweep functionWrappers_, so we have to use relookupOrAdd. We do this in some other places for the same reason.

Comment 9

[Jan de Mooij [:jandem]]

https://hg.mozilla.org/projects/ionmonkey/rev/06338317eaba

Comment 10

[Christian Holler (:decoder)]

Testcase is too complex to add.