cgroup: remove css_scan_tasks()
css_scan_tasks() doesn't have any user left. Remove it. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
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Tejun Heo
parent
d66393e54e
commit
889ed9ceaa
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@ -14,7 +14,6 @@
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#include <linux/rcupdate.h>
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#include <linux/rculist.h>
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#include <linux/cgroupstats.h>
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#include <linux/prio_heap.h>
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#include <linux/rwsem.h>
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#include <linux/idr.h>
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#include <linux/workqueue.h>
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@ -813,11 +812,6 @@ void css_task_iter_start(struct cgroup_subsys_state *css,
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struct task_struct *css_task_iter_next(struct css_task_iter *it);
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void css_task_iter_end(struct css_task_iter *it);
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int css_scan_tasks(struct cgroup_subsys_state *css,
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bool (*test)(struct task_struct *, void *),
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void (*process)(struct task_struct *, void *),
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void *data, struct ptr_heap *heap);
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int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
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int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
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162
kernel/cgroup.c
162
kernel/cgroup.c
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@ -2697,168 +2697,6 @@ void css_task_iter_end(struct css_task_iter *it)
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up_read(&css_set_rwsem);
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}
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static inline int started_after_time(struct task_struct *t1,
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struct timespec *time,
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struct task_struct *t2)
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{
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int start_diff = timespec_compare(&t1->start_time, time);
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if (start_diff > 0) {
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return 1;
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} else if (start_diff < 0) {
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return 0;
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} else {
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/*
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* Arbitrarily, if two processes started at the same
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* time, we'll say that the lower pointer value
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* started first. Note that t2 may have exited by now
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* so this may not be a valid pointer any longer, but
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* that's fine - it still serves to distinguish
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* between two tasks started (effectively) simultaneously.
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*/
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return t1 > t2;
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}
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}
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/*
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* This function is a callback from heap_insert() and is used to order
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* the heap.
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* In this case we order the heap in descending task start time.
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*/
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static inline int started_after(void *p1, void *p2)
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{
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struct task_struct *t1 = p1;
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struct task_struct *t2 = p2;
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return started_after_time(t1, &t2->start_time, t2);
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}
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/**
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* css_scan_tasks - iterate though all the tasks in a css
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* @css: the css to iterate tasks of
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* @test: optional test callback
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* @process: process callback
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* @data: data passed to @test and @process
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* @heap: optional pre-allocated heap used for task iteration
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*
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* Iterate through all the tasks in @css, calling @test for each, and if it
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* returns %true, call @process for it also.
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*
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* @test may be NULL, meaning always true (select all tasks), which
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* effectively duplicates css_task_iter_{start,next,end}() but does not
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* lock css_set_rwsem for the call to @process.
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*
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* It is guaranteed that @process will act on every task that is a member
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* of @css for the duration of this call. This function may or may not
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* call @process for tasks that exit or move to a different css during the
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* call, or are forked or move into the css during the call.
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*
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* Note that @test may be called with locks held, and may in some
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* situations be called multiple times for the same task, so it should be
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* cheap.
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*
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* If @heap is non-NULL, a heap has been pre-allocated and will be used for
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* heap operations (and its "gt" member will be overwritten), else a
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* temporary heap will be used (allocation of which may cause this function
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* to fail).
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*/
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int css_scan_tasks(struct cgroup_subsys_state *css,
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bool (*test)(struct task_struct *, void *),
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void (*process)(struct task_struct *, void *),
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void *data, struct ptr_heap *heap)
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{
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int retval, i;
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struct css_task_iter it;
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struct task_struct *p, *dropped;
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/* Never dereference latest_task, since it's not refcounted */
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struct task_struct *latest_task = NULL;
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struct ptr_heap tmp_heap;
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struct timespec latest_time = { 0, 0 };
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if (heap) {
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/* The caller supplied our heap and pre-allocated its memory */
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heap->gt = &started_after;
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} else {
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/* We need to allocate our own heap memory */
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heap = &tmp_heap;
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retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after);
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if (retval)
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/* cannot allocate the heap */
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return retval;
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}
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again:
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/*
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* Scan tasks in the css, using the @test callback to determine
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* which are of interest, and invoking @process callback on the
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* ones which need an update. Since we don't want to hold any
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* locks during the task updates, gather tasks to be processed in a
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* heap structure. The heap is sorted by descending task start
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* time. If the statically-sized heap fills up, we overflow tasks
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* that started later, and in future iterations only consider tasks
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* that started after the latest task in the previous pass. This
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* guarantees forward progress and that we don't miss any tasks.
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*/
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heap->size = 0;
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css_task_iter_start(css, &it);
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while ((p = css_task_iter_next(&it))) {
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/*
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* Only affect tasks that qualify per the caller's callback,
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* if he provided one
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*/
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if (test && !test(p, data))
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continue;
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/*
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* Only process tasks that started after the last task
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* we processed
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*/
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if (!started_after_time(p, &latest_time, latest_task))
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continue;
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dropped = heap_insert(heap, p);
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if (dropped == NULL) {
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/*
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* The new task was inserted; the heap wasn't
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* previously full
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*/
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get_task_struct(p);
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} else if (dropped != p) {
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/*
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* The new task was inserted, and pushed out a
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* different task
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*/
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get_task_struct(p);
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put_task_struct(dropped);
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}
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/*
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* Else the new task was newer than anything already in
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* the heap and wasn't inserted
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*/
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}
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css_task_iter_end(&it);
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if (heap->size) {
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for (i = 0; i < heap->size; i++) {
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struct task_struct *q = heap->ptrs[i];
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if (i == 0) {
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latest_time = q->start_time;
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latest_task = q;
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}
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/* Process the task per the caller's callback */
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process(q, data);
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put_task_struct(q);
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}
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/*
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* If we had to process any tasks at all, scan again
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* in case some of them were in the middle of forking
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* children that didn't get processed.
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* Not the most efficient way to do it, but it avoids
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* having to take callback_mutex in the fork path
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*/
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goto again;
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}
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if (heap == &tmp_heap)
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heap_free(&tmp_heap);
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return 0;
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}
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/**
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* cgroup_trasnsfer_tasks - move tasks from one cgroup to another
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* @to: cgroup to which the tasks will be moved
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