[11u] RFR 8255269: Unsigned overflow in g1Policy.cpp

[Hohensee, Paul]

Thanks, lgtm now. I'll tag the issue.

Paul

On 11/3/20, 5:23 PM, "jdk-updates-dev on behalf of Kemper, William" <jdk-updates-dev-retn at openjdk.java.net on behalf of kemperw at amazon.com> wrote:

    Here's a patch based on jdk13u using the Skara CLI tools:

    git hg-export 7e95c0a5
    # HG changeset patch
    # User phh
    # Date 1603811625 0
    #      Tue Oct 15:13:45 2020 +0000
    8255269: Unsigned overflow in g1Policy.cpp
    Reviewed-by: yan
    Contributed-by: William Kemper <kemperw at amazon.com<mailto:kemperw at amazon.com>>

    diff --git a/src/hotspot/share/gc/g1/g1Policy.cpp b/src/hotspot/share/gc/g1/g1Policy.cpp
    index 91eceb7375..dec7f57de6 100644
    --- a/src/hotspot/share/gc/g1/g1Policy.cpp
    +++ b/src/hotspot/share/gc/g1/g1Policy.cpp
    @@ -1,5 +1,5 @@
     /*
    - * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved.
    + * Copyright (c) 2001, 2020, Oracle and/or its affiliates. All rights reserved.
      * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
      *
      * This code is free software; you can redistribute it and/or modify it
    @@ -692,11 +692,11 @@ void G1Policy::record_collection_pause_end(double pause_time_ms, size_t cards_sc
         _analytics->report_rs_length_diff((double) rs_length_diff);

         size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
    -    size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
    -    double cost_per_byte_ms = 0.0;

    -    if (copied_bytes > 0) {
    -      cost_per_byte_ms = (average_time_ms(G1GCPhaseTimes::ObjCopy) + average_time_ms(G1GCPhaseTimes::OptObjCopy)) / (double) copied_bytes;
    +    if (_collection_set->bytes_used_before() > freed_bytes) {
    +      size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
    +      double average_copy_time = average_time_ms(G1GCPhaseTimes::ObjCopy);
    +      double cost_per_byte_ms = average_copy_time / (double) copied_bytes;
           _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress());
         }

    I ran the jtreg tests for G1 against the release build on my workstation (x86, Ubuntu 18.04). The results were the same before and after the patch was applied:

    test/hotspot/jtreg/gc/g1
    Test results: passed: 56; failed: 4; error: 1

    It doesn't look like the failures and error have anything to do with this change.

    Thanks,
    William