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Add a comment documenting a race condition in vm_fault(): Specifically, a

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modification is made to the vm_map while only a read lock is held.
This commit is contained in:
Alan Cox 2002-04-18 03:55:50 +00:00
parent 91e007dc70
commit ff8f4ebe22
1 changed files with 3 additions and 0 deletions
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3
sys/vm/vm_fault.c
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@ -258,6 +258,9 @@ RetryFault:;
* If we don't COW now, on a user wire, the user will never * If we don't COW now, on a user wire, the user will never
* be able to write to the mapping. If we don't make this * be able to write to the mapping. If we don't make this
* restriction, the bookkeeping would be nearly impossible. * restriction, the bookkeeping would be nearly impossible.
*
* XXX The following assignment modifies the map without
* holding a write lock on it.
*/ */
if ((fs.entry->protection & VM_PROT_WRITE) == 0) if ((fs.entry->protection & VM_PROT_WRITE) == 0)
fs.entry->max_protection &= ~VM_PROT_WRITE; fs.entry->max_protection &= ~VM_PROT_WRITE;