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Subject[PATCH 09/16] cgroup: remove css_scan_tasks()
Date
css_scan_tasks() doesn't have any user left.  Remove it.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
include/linux/cgroup.h | 6 --
kernel/cgroup.c | 162 -------------------------------------------------
2 files changed, 168 deletions(-)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index f173cfb..db5ccf4 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -14,7 +14,6 @@
#include <linux/rcupdate.h>
#include <linux/rculist.h>
#include <linux/cgroupstats.h>
-#include <linux/prio_heap.h>
#include <linux/rwsem.h>
#include <linux/idr.h>
#include <linux/workqueue.h>
@@ -811,11 +810,6 @@ void css_task_iter_start(struct cgroup_subsys_state *css,
struct task_struct *css_task_iter_next(struct css_task_iter *it);
void css_task_iter_end(struct css_task_iter *it);

-int css_scan_tasks(struct cgroup_subsys_state *css,
- bool (*test)(struct task_struct *, void *),
- void (*process)(struct task_struct *, void *),
- void *data, struct ptr_heap *heap);
-
int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 5ad1b25..8c1f840 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2696,168 +2696,6 @@ void css_task_iter_end(struct css_task_iter *it)
up_read(&css_set_rwsem);
}

-static inline int started_after_time(struct task_struct *t1,
- struct timespec *time,
- struct task_struct *t2)
-{
- int start_diff = timespec_compare(&t1->start_time, time);
- if (start_diff > 0) {
- return 1;
- } else if (start_diff < 0) {
- return 0;
- } else {
- /*
- * Arbitrarily, if two processes started at the same
- * time, we'll say that the lower pointer value
- * started first. Note that t2 may have exited by now
- * so this may not be a valid pointer any longer, but
- * that's fine - it still serves to distinguish
- * between two tasks started (effectively) simultaneously.
- */
- return t1 > t2;
- }
-}
-
-/*
- * This function is a callback from heap_insert() and is used to order
- * the heap.
- * In this case we order the heap in descending task start time.
- */
-static inline int started_after(void *p1, void *p2)
-{
- struct task_struct *t1 = p1;
- struct task_struct *t2 = p2;
- return started_after_time(t1, &t2->start_time, t2);
-}
-
-/**
- * css_scan_tasks - iterate though all the tasks in a css
- * @css: the css to iterate tasks of
- * @test: optional test callback
- * @process: process callback
- * @data: data passed to @test and @process
- * @heap: optional pre-allocated heap used for task iteration
- *
- * Iterate through all the tasks in @css, calling @test for each, and if it
- * returns %true, call @process for it also.
- *
- * @test may be NULL, meaning always true (select all tasks), which
- * effectively duplicates css_task_iter_{start,next,end}() but does not
- * lock css_set_rwsem for the call to @process.
- *
- * It is guaranteed that @process will act on every task that is a member
- * of @css for the duration of this call. This function may or may not
- * call @process for tasks that exit or move to a different css during the
- * call, or are forked or move into the css during the call.
- *
- * Note that @test may be called with locks held, and may in some
- * situations be called multiple times for the same task, so it should be
- * cheap.
- *
- * If @heap is non-NULL, a heap has been pre-allocated and will be used for
- * heap operations (and its "gt" member will be overwritten), else a
- * temporary heap will be used (allocation of which may cause this function
- * to fail).
- */
-int css_scan_tasks(struct cgroup_subsys_state *css,
- bool (*test)(struct task_struct *, void *),
- void (*process)(struct task_struct *, void *),
- void *data, struct ptr_heap *heap)
-{
- int retval, i;
- struct css_task_iter it;
- struct task_struct *p, *dropped;
- /* Never dereference latest_task, since it's not refcounted */
- struct task_struct *latest_task = NULL;
- struct ptr_heap tmp_heap;
- struct timespec latest_time = { 0, 0 };
-
- if (heap) {
- /* The caller supplied our heap and pre-allocated its memory */
- heap->gt = &started_after;
- } else {
- /* We need to allocate our own heap memory */
- heap = &tmp_heap;
- retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after);
- if (retval)
- /* cannot allocate the heap */
- return retval;
- }
-
- again:
- /*
- * Scan tasks in the css, using the @test callback to determine
- * which are of interest, and invoking @process callback on the
- * ones which need an update. Since we don't want to hold any
- * locks during the task updates, gather tasks to be processed in a
- * heap structure. The heap is sorted by descending task start
- * time. If the statically-sized heap fills up, we overflow tasks
- * that started later, and in future iterations only consider tasks
- * that started after the latest task in the previous pass. This
- * guarantees forward progress and that we don't miss any tasks.
- */
- heap->size = 0;
- css_task_iter_start(css, &it);
- while ((p = css_task_iter_next(&it))) {
- /*
- * Only affect tasks that qualify per the caller's callback,
- * if he provided one
- */
- if (test && !test(p, data))
- continue;
- /*
- * Only process tasks that started after the last task
- * we processed
- */
- if (!started_after_time(p, &latest_time, latest_task))
- continue;
- dropped = heap_insert(heap, p);
- if (dropped == NULL) {
- /*
- * The new task was inserted; the heap wasn't
- * previously full
- */
- get_task_struct(p);
- } else if (dropped != p) {
- /*
- * The new task was inserted, and pushed out a
- * different task
- */
- get_task_struct(p);
- put_task_struct(dropped);
- }
- /*
- * Else the new task was newer than anything already in
- * the heap and wasn't inserted
- */
- }
- css_task_iter_end(&it);
-
- if (heap->size) {
- for (i = 0; i < heap->size; i++) {
- struct task_struct *q = heap->ptrs[i];
- if (i == 0) {
- latest_time = q->start_time;
- latest_task = q;
- }
- /* Process the task per the caller's callback */
- process(q, data);
- put_task_struct(q);
- }
- /*
- * If we had to process any tasks at all, scan again
- * in case some of them were in the middle of forking
- * children that didn't get processed.
- * Not the most efficient way to do it, but it avoids
- * having to take callback_mutex in the fork path
- */
- goto again;
- }
- if (heap == &tmp_heap)
- heap_free(&tmp_heap);
- return 0;
-}
-
/**
* cgroup_trasnsfer_tasks - move tasks from one cgroup to another
* @to: cgroup to which the tasks will be moved
--
1.8.5.3


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