[Mono-dev] Deadlock in System.Web.Caching.Cache class

[Marek Habersack]

Ivan Radovanovic wrote:
> Although this dead lock problem continues to potentially exists it seems 
> that problem is after all OS specific - there is some weird behavior of 
> fam/gamin reporting that bin/*.dll files are changed, causing ASP.Net 
> runtime trying to restart application, while at the same time trying to 
> compile *.aspx, *.ascx etc.
The issue might be in FAM FileSystemWatcher backend then.

> Maybe deadlock can occur in normal conditions too (servicing some 
> request that would need compiling of some control/page that is not 
> compiled yet and replacing something in bin directory at the same time), 
> but that should be rare enough :-)
The BuildManager in 2.4 has some bugs indeed, which in certain cases can lead to deadlocks (it's, 
among others, related to recursive dependencies between application files). For that reason I 
rewrote BuildManager for 2.6+ - if the problem you're seeing turns out to be an issue with more than 
few environments, I can just copy the new code to 2.4 branch for a future release. If you can come 
up with a test case that triggers the issue on your system, then please file a bug report and attach 
the testcase including OS/environment details.

marek
> 
> Regards
> 
> Ivan Radovanovic napisa:
>> Hello, I am experiencing weird deadlock in .net applications running 
>> latest release version of mono (2.4.2.3) on FreeBSD (I don't think it is 
>> OS specific, and it doesn't show all the times, but still often enough 
>> so I can trace it)
>>
>> Stack from thread 1:
>>    at 
>> System.Web.Compilation.BuildManager.RemoveVirtualPathFromCaches(System.Web.VirtualPath 
>> virtualPath)
>>    at 
>> System.Web.Compilation.BuildManager.OnVirtualPathChanged(System.String 
>> key, System.Object value, CacheItemRemovedReason removedReason)
>>    at System.Web.Caching.Cache.InvokePrivateCallbacks()
>>    at System.Web.HttpRuntime.ShutdownAppDomain(System.Object args)
>> ====================================================================
>> Stack from thread 2:
>>    at System.Web.Caching.Cache.Add(System.String key, System.Object 
>> value, System.Web.Caching.CacheDependency dependencies, DateTime 
>> absoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority 
>> priority, System.Web.Caching.CacheItemRemovedCallback onRemoveCallback)
>>    at System.Web.Compilation.BuildManager.AddToCache(System.String 
>> virtualPath, System.Web.Compilation.BuildProvider bp)
>>    at 
>> System.Web.Compilation.BuildManager.GenerateAssembly(System.Web.Compilation.AssemblyBuilder 
>> abuilder, System.Collections.Generic.List`1 buildItems, 
>> System.Web.VirtualPath virtualPath, BuildKind buildKind)
>>    at 
>> System.Web.Compilation.BuildManager.BuildAssembly(System.Web.VirtualPath 
>> virtualPath)
>>    at System.Web.Compilation.BuildManager.GetCompiledType(System.String 
>> virtualPath)
>>    at System.Web.Compilation.AspComponentFoundry+TagNameFoundry.LoadType()
>>    at 
>> System.Web.Compilation.AspComponentFoundry+TagNameFoundry.GetType(System.String 
>> componentName, System.String ByRef source, System.String ByRef ns)
>>    at 
>> System.Web.Compilation.AspComponentFoundry.CreateComponent(System.Web.Compilation.Foundry 
>> foundry, System.String tagName, System.String prefix, System.String tag)
>>    at 
>> System.Web.Compilation.AspComponentFoundry.GetComponent(System.String 
>> tagName)
>>    at System.Web.UI.RootBuilder.GetChildControlType(System.String 
>> tagName, IDictionary attribs)
>>    at System.Web.UI.ControlBuilder.CreateSubBuilder(System.String tagid, 
>> System.Collections.Hashtable atts, System.Type childType, 
>> System.Web.UI.TemplateParser parser, ILocation location)
>>    at System.Web.Compilation.AspGenerator.ProcessTag(ILocation location, 
>> System.String tagid, System.Web.Compilation.TagAttributes atts, TagType 
>> tagtype, Boolean ByRef ignored)
>>    at System.Web.Compilation.AspGenerator.TagParsed(ILocation location, 
>> TagType tagtype, System.String tagid, 
>> System.Web.Compilation.TagAttributes attributes)
>>    at System.Web.Compilation.AspParser.OnTagParsed(TagType tagtype, 
>> System.String id, System.Web.Compilation.TagAttributes attributes)
>>    at System.Web.Compilation.AspParser.Parse()
>>    at System.Web.Compilation.AspGenerator.Parse(System.IO.TextReader 
>> reader, System.String filename, Boolean doInitParser)
>>    at System.Web.Compilation.GenericBuildProvider`1.Parse()
>>    at System.Web.Compilation.GenericBuildProvider`1.get_CodeCompilerType()
>>    at 
>> System.Web.Compilation.BuildManager.GetCodeDomProviderType(System.Web.Compilation.BuildProvider 
>> provider)
>>    at 
>> System.Web.Compilation.BuildManager+BuildItem..ctor(System.Web.Compilation.BuildProvider 
>> provider)
>>    at 
>> System.Web.Compilation.BuildManager.LoadBuildProviders(System.Web.VirtualPath 
>> virtualPath, System.String virtualDir, 
>> System.Collections.Generic.Dictionary`2 vpCache, BuildKind ByRef kind, 
>> System.String ByRef assemblyBaseName)
>>    at 
>> System.Web.Compilation.BuildManager.BuildAssembly(System.Web.VirtualPath 
>> virtualPath)
>>    at System.Web.Compilation.BuildManager.GetCompiledType(System.String 
>> virtualPath)
>>    at System.Web.Compilation.AspComponentFoundry+TagNameFoundry.LoadType()
>>    at 
>> System.Web.Compilation.AspComponentFoundry+TagNameFoundry.GetType(System.String 
>> componentName, System.String ByRef source, System.String ByRef ns)
>>    at 
>> System.Web.Compilation.AspComponentFoundry.CreateComponent(System.Web.Compilation.Foundry 
>> foundry, System.String tagName, System.String prefix, System.String tag)
>>    at 
>> System.Web.Compilation.AspComponentFoundry.GetComponent(System.String 
>> tagName)
>>    at System.Web.UI.RootBuilder.GetChildControlType(System.String 
>> tagName, IDictionary attribs)
>>    at System.Web.UI.ControlBuilder.CreateSubBuilder(System.String tagid, 
>> System.Collections.Hashtable atts, System.Type childType, 
>> System.Web.UI.TemplateParser parser, ILocation location)
>>    at System.Web.Compilation.AspGenerator.ProcessTag(ILocation location, 
>> System.String tagid, System.Web.Compilation.TagAttributes atts, TagType 
>> tagtype, Boolean ByRef ignored)
>>    at System.Web.Compilation.AspGenerator.TagParsed(ILocation location, 
>> TagType tagtype, System.String tagid, 
>> System.Web.Compilation.TagAttributes attributes)
>>    at System.Web.Compilation.AspParser.OnTagParsed(TagType tagtype, 
>> System.String id, System.Web.Compilation.TagAttributes attributes)
>>    at System.Web.Compilation.AspParser.Parse()
>>    at System.Web.Compilation.AspGenerator.Parse(System.IO.TextReader 
>> reader, System.String filename, Boolean doInitParser)
>>    at System.Web.Compilation.GenericBuildProvider`1.Parse()
>>    at System.Web.Compilation.GenericBuildProvider`1.get_CodeCompilerType()
>>    at 
>> System.Web.Compilation.BuildManager.GetCodeDomProviderType(System.Web.Compilation.BuildProvider 
>> provider)
>>    at 
>> System.Web.Compilation.BuildManager+BuildItem..ctor(System.Web.Compilation.BuildProvider 
>> provider)
>>    at 
>> System.Web.Compilation.BuildManager.LoadBuildProviders(System.Web.VirtualPath 
>> virtualPath, System.String virtualDir, 
>> System.Collections.Generic.Dictionary`2 vpCache, BuildKind ByRef kind, 
>> System.String ByRef assemblyBaseName)
>>    at 
>> System.Web.Compilation.BuildManager.BuildAssembly(System.Web.VirtualPath 
>> virtualPath)
>>    at System.Web.Compilation.BuildManager.GetCompiledType(System.String 
>> virtualPath)
>>    at 
>> System.Web.Compilation.BuildManager.CreateInstanceFromVirtualPath(System.String 
>> virtualPath, System.Type requiredBaseType)
>>    at System.Web.UI.PageParser.GetCompiledPageInstance(System.String 
>> virtualPath, System.String inputFile, System.Web.HttpContext context)
>>    at System.Web.UI.PageHandlerFactory.GetHandler(System.Web.HttpContext 
>> context, System.String requestType, System.String url, System.String path)
>>    at System.Web.HttpApplication.GetHandler(System.Web.HttpContext 
>> context, System.String url, Boolean ignoreContextHandler)
>>    at System.Web.HttpApplication.GetHandler(System.Web.HttpContext 
>> context, System.String url)
>>    at System.Web.HttpApplication+<Pipeline>c__Iterator2.MoveNext()
>>    at System.Web.HttpApplication.Tick()
>>    at System.Web.HttpApplication.Start(System.Object x)
>>    at 
>> System.Web.HttpApplication.System.Web.IHttpHandler.ProcessRequest(System.Web.HttpContext 
>> context)
>>    at System.Web.HttpRuntime.Process(System.Web.HttpWorkerRequest req)
>>    at System.Web.HttpRuntime.RealProcessRequest(System.Object o)
>>    at System.Web.HttpRuntime.ProcessRequest(System.Web.HttpWorkerRequest 
>> wr)
>>    at Mono.WebServer.MonoWorkerRequest.ProcessRequest()
>>    at 
>> Mono.WebServer.BaseApplicationHost.ProcessRequest(Mono.WebServer.MonoWorkerRequest 
>> mwr)
>>    at Mono.WebServer.XSPApplicationHost.ProcessRequest(Int32 reqId, 
>> Int64 localEPAddr, Int32 localEPPort, Int64 remoteEPAdds, Int32 
>> remoteEPPort, System.String verb, System.String path, System.String 
>> queryString, System.String protocol, System.Byte[] inputBuffer, 
>> System.String redirect, IntPtr socket, Mono.WebServer.SslInformations ssl)
>>    at Mono.WebServer.XSPWorker.RunInternal(System.Object state)
>> =============================================================================== 
>>
>>
>> As you can see there is deadlock between 
>> System.Web.Compilation.BuildManager.AddToCache (thread 2, second item) 
>> and System.Web.Compilation.BuildManager.GenerateAssembly (both using 
>> lock (buildCacheLock)) and between System.Web.Caching.Cache.Add and 
>> System.Web.Caching.Cache.InvokePrivateCallbacks() (both using lock(cache))
>>
>> I am curious if someone is working on this bug (is this known bug?) or I 
>> should try to fix it myself?
>>
>> Best regards,
>> Ivan
>>
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