I noticed this issue while reviewing the code of Mapper.removeContextVersion() of the current trunk (@1604217). The same code exists in Tomcat 7 and 6.

In Mapper.removeContextVersion() (Mapper.removeContext() in Tomcat 6) it does the following:
[[[
host.contextList.contexts = newContexts;             
// Recalculate nesting                               
host.contextList.nesting = 0;                        
for (int i = 0; i < newContexts.length; i++) {       
    int slashCount = slashCount(newContexts[i].name);
    if (slashCount > host.contextList.nesting) {     
        host.contextList.nesting = slashCount;       
    }                                                
}                                                    
]]]

The problem is there is a delay between when the list of contexts is updated (contextList.contexts) and the contextList.nesting field is updated. The "nesting" field is used when mapping contexts.

For example,
1. If there are the following contexts:
ROOT
foo
foo#bar

2. Context foo#bar is being stopped.

3. A request for "foo" comes in, e.g. http://localhost/foo/index.html
Expected behaviour: Map the context to foo application.
Actual behaviour:
It may be that the request will be erroneously mapped to the ROOT webapp instead of "foo".

I have a test case.