[PATCH] cpuset: remove marker_pid documentation

Remove documentation for the cpuset 'marker_pid' feature, that was in the
patch "cpuset: change marker for relative numbering" That patch was previously
pulled from *-mm at my (pj) request.

Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Documentation/cpusets.txt

@@ -16,9 +16,8 @@ CONTENTS:
   1.3 How are cpusets implemented ?
   1.4 What are exclusive cpusets ?
   1.5 What does notify_on_release do ?
-  1.6 What is a marker_pid ?
+  1.6 What is memory_pressure ?
-  1.7 What is memory_pressure ?
+  1.7 How do I use cpusets ?
-  1.8 How do I use cpusets ?
 2. Usage Examples and Syntax
   2.1 Basic Usage
   2.2 Adding/removing cpus
@@ -178,7 +177,6 @@ containing the following files describing that cpuset:
  - mem_exclusive flag: is memory placement exclusive?
  - tasks: list of tasks (by pid) attached to that cpuset
  - notify_on_release flag: run /sbin/cpuset_release_agent on exit?
- - marker_pid: pid of user task in co-ordinated operation sequence
  - memory_pressure: measure of how much paging pressure in cpuset
 
 In addition, the root cpuset only has the following file:
@@ -260,47 +258,7 @@ boot is disabled (0).  The default value of other cpusets at creation
 is the current value of their parents notify_on_release setting.
 
 
-1.6 What is a marker_pid ?
+1.6 What is memory_pressure ?
---------------------------
-
-The marker_pid helps manage cpuset changes safely from user space.
-
-The interface presented to user space for cpusets uses system wide
-numbering of CPUs and Memory Nodes.   It is the responsibility of
-user level code, presumably in a library, to present cpuset-relative
-numbering to applications when that would be more useful to them.
-
-However if a task is moved to a different cpuset, or if the 'cpus' or
-'mems' of a cpuset are changed, then we need a way for such library
-code to detect that its cpuset-relative numbering has changed, when
-expressed using system wide numbering.
-
-The kernel cannot safely allow user code to lock kernel resources.
-The kernel could deliver out-of-band notice of cpuset changes by
-such mechanisms as signals or usermodehelper callbacks, however
-this can't be synchronously delivered to library code linked in
-applications without intruding on the IPC mechanisms available to
-the app.  The kernel could require user level code to do all the work,
-tracking the cpuset state before and during changes, to verify no
-unexpected change occurred, but this becomes an onerous task.
-
-The "marker_pid" cpuset field provides a simple way to make this task
-less onerous on user library code.  A task writes its pid to a cpusets
-"marker_pid" at the start of a sequence of queries and updates,
-and check as it goes that the cpusets marker_pid doesn't change.
-The pread(2) system call does a seek and read in a single call.
-If the marker_pid changes, the user code should retry the required
-sequence of operations.
-
-Anytime that a task modifies the "cpus" or "mems" of a cpuset,
-unless it's pid is in the cpusets marker_pid field, the kernel zeros
-this field.
-
-The above was inspired by the load linked and store conditional
-(ll/sc) instructions in the MIPS II instruction set.
-
-
-1.7 What is memory_pressure ?
 -----------------------------
 The memory_pressure of a cpuset provides a simple per-cpuset metric
 of the rate that the tasks in a cpuset are attempting to free up in
@@ -357,7 +315,7 @@ the tasks in the cpuset, in units of reclaims attempted per second,
 times 1000.
 
 
-1.8 How do I use cpusets ?
+1.7 How do I use cpusets ?
 --------------------------
 
 In order to minimize the impact of cpusets on critical kernel