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Fix potential deadlocking behaviour (and convert ResetEvent to Semaphore)

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This commit is contained in:
Dean Herbert 2021-06-24 14:37:26 +09:00
parent c85edd2b55
commit 63ab40ec24
1 changed files with 43 additions and 28 deletions
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55
osu.Game/Database/RealmContextFactory.cs
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@ -26,6 +26,11 @@ namespace osu.Game.Database
/// </summary>
private readonly object writeLock = new object();
/// <summary>
/// Lock object which is held during <see cref="BlockAllOperations"/> sections.
/// </summary>
private readonly SemaphoreSlim blockingLock = new SemaphoreSlim(1);
private static readonly GlobalStatistic<int> reads = GlobalStatistics.Get<int>("Realm", "Get (Read)");
private static readonly GlobalStatistic<int> writes = GlobalStatistics.Get<int>("Realm", "Get (Write)");
private static readonly GlobalStatistic<int> refreshes = GlobalStatistics.Get<int>("Realm", "Dirty Refreshes");
@ -33,8 +38,6 @@ namespace osu.Game.Database
private static readonly GlobalStatistic<int> pending_writes = GlobalStatistics.Get<int>("Realm", "Pending writes");
private static readonly GlobalStatistic<int> active_usages = GlobalStatistics.Get<int>("Realm", "Active usages");
private readonly ManualResetEventSlim blockingResetEvent = new ManualResetEventSlim(true);
private Realm context;
public Realm Context
@ -64,7 +67,7 @@ namespace osu.Game.Database
public RealmUsage GetForRead()
{
reads.Value++;
return new RealmUsage(this);
return new RealmUsage(createContext());
}
public RealmWriteUsage GetForWrite()
@ -73,8 +76,13 @@ namespace osu.Game.Database
pending_writes.Value++;
Monitor.Enter(writeLock);
return new RealmWriteUsage(createContext(), writeComplete);
}
return new RealmWriteUsage(this);
private void writeComplete()
{
Monitor.Exit(writeLock);
pending_writes.Value--;
}
protected override void Update()
@ -87,7 +95,9 @@ namespace osu.Game.Database
private Realm createContext()
{
blockingResetEvent.Wait();
try
{
blockingLock.Wait();
contexts_created.Value++;
@ -97,6 +107,11 @@ namespace osu.Game.Database
MigrationCallback = onMigration,
});
}
finally
{
blockingLock.Release();
}
}
private void onMigration(Migration migration, ulong lastSchemaVersion)
{
@ -113,21 +128,23 @@ namespace osu.Game.Database
{
base.Dispose(isDisposing);
// In the standard case, operations will already be blocked by the Update thread "pausing" from GameHost exit.
// This avoids waiting (forever) on an already entered semaphore.
if (context != null || active_usages.Value > 0)
BlockAllOperations();
blockingLock?.Dispose();
}
public IDisposable BlockAllOperations()
{
blockingResetEvent.Reset();
blockingLock.Wait();
flushContexts();
return new InvokeOnDisposal<RealmContextFactory>(this, r => endBlockingSection());
return new InvokeOnDisposal<RealmContextFactory>(this, endBlockingSection);
}
private void endBlockingSection()
{
blockingResetEvent.Set();
}
private static void endBlockingSection(RealmContextFactory factory) => factory.blockingLock.Release();
private void flushContexts()
{
@ -148,13 +165,10 @@ namespace osu.Game.Database
{
public readonly Realm Realm;
protected readonly RealmContextFactory Factory;
internal RealmUsage(RealmContextFactory factory)
internal RealmUsage(Realm context)
{
active_usages.Value++;
Factory = factory;
Realm = factory.createContext();
Realm = context;
}
/// <summary>
@ -172,11 +186,13 @@ namespace osu.Game.Database
/// </summary>
public class RealmWriteUsage : RealmUsage
{
private readonly Action onWriteComplete;
private readonly Transaction transaction;
internal RealmWriteUsage(RealmContextFactory factory)
: base(factory)
internal RealmWriteUsage(Realm context, Action onWriteComplete)
: base(context)
{
this.onWriteComplete = onWriteComplete;
transaction = Realm.BeginWrite();
}
@ -200,8 +216,7 @@ namespace osu.Game.Database
base.Dispose();
Monitor.Exit(Factory.writeLock);
pending_writes.Value--;
onWriteComplete();
}
}
}