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xen-devel
[Xen-devel] Re: Should shadow_lock be spin_lock_recursive?
This dead lock happened on VNIF code when enabled shadow mode.
The shadow_lock path is so complex and maybe using recurisve lock
is the easiest way to avoid dead lock currently before clearing
the path or splitting the lock .
Arun Sharma wrote:
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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