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doc: shadow variable notes

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Joe Lawrence 2017-04-13 10:45:06 -04:00
parent dd18205539
commit e124028b65
1 changed files with 10 additions and 1 deletions
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doc/patch-author-guide.md
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@ -160,7 +160,7 @@ If you need to add a field to an existing data structure, or even many existing
data structures, you can use the `kpatch_shadow_*()` functions:
* `kpatch_shadow_alloc` - allocates a new shadow variable associated with a
given object.
given object
* `kpatch_shadow_get` - find and return a pointer to a shadow variable
* `kpatch_shadow_free` - find and free a shadow variable
@ -214,6 +214,15 @@ safe to access:
* Flush inherited counters to the parent - before the parent
* gets woken up by child-exit notifications.
```
Notes:
* `kpatch_shadow_alloc` initializes only shadow variable metadata. It
allocates variable storage via `kmalloc` with the `gfp_t` flags it is
given, but otherwise leaves the area untouched. Initialization of a shadow
variable is the responsibility of the caller.
* As soon as `kpatch_shadow_alloc` creates a shadow variable, its presence
will be reported by `kpatch_shadow_get`. Care should be taken to avoid any
potential race conditions between a kernel thread that allocates a shadow
variable and concurrent threads that may attempt to use it.
Data semantic changes
---------------------