Hello. hugetlb_instantiation_mutex is an extremely heavy-weight lock
whose days are numbered (hopefully). It exists primarily to arbitrate
a race condition where n (n > 1) threads of execution race to satisfy
the same page fault for a process. Even though only one hugetlb page
is needed, if (n) are not available, the application can receive a
bogus VM_FAULT_OOM.
Anyway, the hugetlb_instantiation_mutex approach has few friends
around here, so rather than making the code rely more heavily upon it,
perhaps you could focus you efforts on helping us remove it.
On 7/23/07, Zhang, Yanmin <[email protected]> wrote:
Function hugetlb_fault needn't hold spinlock mm->page_table_lock,
because when hugetlb_fault is called:
1) mm->mmap_sem is held already;
2) hugetlb_instantiation_mutex is held by hugetlb_fault, which prevents
other threads/processes from entering this critical area. It's impossible
for other threads/processes to change the page table now.
--
Adam Litke ( agl at us.ibm.com )
IBM Linux Technology Center
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