[Xen-devel] Should shadow_lock be spin_lock_recursive?

[Arun Sharma <arun.sharma@xxxxxxxxx>]

During our testing, we found this code path where xen attempts to grab 
the shadow_lock, while holding it - leading to a deadlock.
>> free_dom_mem->
>> shadow_sync_and_drop_references->
>> shadow_lock -> ..................... first lock
>> shadow_remove_all_access->
>> remove_all_access_in_page->
>> put_page->
>> free_domheap_pages->
>> shadow_drop_references->
>> shadow_lock -> ..................... second lock

Questions:

- should shadow lock be recursive?
- is shadow lock too coarse grained? It seems to have led to a lot of 
code refactoring (__foo without lock and foo with lock). But there may 
be more such instances we haven't found yet.
        -Arun

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