get_futex_key
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## Name

get_futex_key — Get parameters which are the keys for a futex

## Synopsis

`int get_futex_key (` | u32 __user * uaddr,
| int fshared,
| union futex_key * key,
| int rw`)`;

## Arguments

`uaddr`

  virtual address of the futex

`fshared`

  0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED

`key`

  address where result is stored.

`rw`

  mapping needs to be read/write (values: VERIFY_READ, VERIFY_WRITE)

## Return

a negative error code or 0

The key words are stored in *key on success.

For shared mappings, it's (page->index, file_inode(vma->vm_file), offset_within_page). For private mappings, it's (uaddr, current->mm). We can usually work out the index without swapping in the page.

`lock_page` might sleep, the caller should not hold a spinlock.

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