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Bug 1397130 - Use signed integer for gUnusedAtomCount. r=froydnj

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MozReview-Commit-ID: 9KweZdyu5WF

--HG--
extra : rebase_source : 81981c706fbde89b18168e39b15dee0cbff27cca
This commit is contained in:
Xidorn Quan 2017-09-06 15:06:16 +10:00
parent ab2b6fc21f
commit 306241f7a1
2 changed files with 15 additions and 8 deletions
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17
xpcom/ds/nsAtomTable.cpp
View File

@ -67,7 +67,14 @@ class CheckStaticAtomSizes
//----------------------------------------------------------------------
static Atomic<uint32_t, ReleaseAcquire> gUnusedAtomCount(0);
// gUnusedAtomCount is incremented when an atom loses its last reference
// (and thus turned into unused state), and decremented when an unused
// atom gets a reference again. The atom table relies on this value to
// schedule GC. This value can temporarily go below zero when multiple
// threads are operating the same atom, so it has to be signed so that
// we wouldn't use overflow value for comparison.
// See Atom::DynamicAddRef and Atom::DynamicRelease.
static Atomic<int32_t, ReleaseAcquire> gUnusedAtomCount(0);
#if defined(NS_BUILD_REFCNT_LOGGING)
// nsFakeStringBuffers don't really use the refcounting system, but we
@ -406,7 +413,7 @@ Atom::GCAtomTableLocked(const MutexAutoLock& aProofOfLock, GCKind aKind)
sRecentlyUsedMainThreadAtoms[i] = nullptr;
}
uint32_t removedCount = 0; // Use a non-atomic temporary for cheaper increments.
int32_t removedCount = 0; // Use a non-atomic temporary for cheaper increments.
nsAutoCString nonZeroRefcountAtoms;
uint32_t nonZeroRefcountAtomsCount = 0;
for (auto i = gAtomTable->Iter(); !i.Done(); i.Next()) {
@ -480,9 +487,9 @@ Atom::DynamicAddRef()
#ifdef DEBUG
// We set a lower GC threshold for atoms in debug builds so that we exercise
// the GC machinery more often.
static const uint32_t kAtomGCThreshold = 20;
static const int32_t kAtomGCThreshold = 20;
#else
static const uint32_t kAtomGCThreshold = 10000;
static const int32_t kAtomGCThreshold = 10000;
#endif
MozExternalRefCountType
@ -796,7 +803,7 @@ NS_GetNumberOfAtoms(void)
return gAtomTable->EntryCount();
}
uint32_t
int32_t
NS_GetUnusedAtomCount(void)
{
return gUnusedAtomCount;

6
xpcom/tests/gtest/TestAtoms.cpp
View File

@ -17,7 +17,7 @@
using namespace mozilla;
uint32_t NS_GetUnusedAtomCount(void);
int32_t NS_GetUnusedAtomCount(void);
namespace TestAtoms {
@ -177,7 +177,7 @@ TEST(Atoms, ConcurrentAccessing)
static const size_t kThreadCount = 4;
// Force a GC before so that we don't have any unused atom.
NS_GetNumberOfAtoms();
EXPECT_EQ(NS_GetUnusedAtomCount(), uint32_t(0));
EXPECT_EQ(NS_GetUnusedAtomCount(), int32_t(0));
nsCOMPtr<nsIThread> threads[kThreadCount];
for (size_t i = 0; i < kThreadCount; i++) {
nsresult rv = NS_NewThread(getter_AddRefs(threads[i]), new nsAtomRunner);
@ -187,7 +187,7 @@ TEST(Atoms, ConcurrentAccessing)
threads[i]->Shutdown();
}
// We should have one unused atom from this test.
EXPECT_EQ(NS_GetUnusedAtomCount(), uint32_t(1));
EXPECT_EQ(NS_GetUnusedAtomCount(), int32_t(1));
}
}