Fix cpusets update_cpumask
Cause writes to cpuset "cpus" file to update cpus_allowed for member tasks:
- collect batches of tasks under tasklist_lock and then call
set_cpus_allowed() on them outside the lock (since this can sleep).
- add a simple generic priority heap type to allow efficient collection
of batches of tasks to be processed without duplicating or missing any
tasks in subsequent batches.
- make "cpus" file update a no-op if the mask hasn't changed
- fix race between update_cpumask() and sched_setaffinity() by making
sched_setaffinity() post-check that it's not running on any cpus outside
cpuset_cpus_allowed().
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Paul Menage <menage@google.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/lib/prio_heap.c b/lib/prio_heap.c
new file mode 100644
index 0000000..471944a
--- /dev/null
+++ b/lib/prio_heap.c
@@ -0,0 +1,70 @@
+/*
+ * Simple insertion-only static-sized priority heap containing
+ * pointers, based on CLR, chapter 7
+ */
+
+#include <linux/slab.h>
+#include <linux/prio_heap.h>
+
+int heap_init(struct ptr_heap *heap, size_t size, gfp_t gfp_mask,
+ int (*gt)(void *, void *))
+{
+ heap->ptrs = kmalloc(size, gfp_mask);
+ if (!heap->ptrs)
+ return -ENOMEM;
+ heap->size = 0;
+ heap->max = size / sizeof(void *);
+ heap->gt = gt;
+ return 0;
+}
+
+void heap_free(struct ptr_heap *heap)
+{
+ kfree(heap->ptrs);
+}
+
+void *heap_insert(struct ptr_heap *heap, void *p)
+{
+ void *res;
+ void **ptrs = heap->ptrs;
+ int pos;
+
+ if (heap->size < heap->max) {
+ /* Heap insertion */
+ int pos = heap->size++;
+ while (pos > 0 && heap->gt(p, ptrs[(pos-1)/2])) {
+ ptrs[pos] = ptrs[(pos-1)/2];
+ pos = (pos-1)/2;
+ }
+ ptrs[pos] = p;
+ return NULL;
+ }
+
+ /* The heap is full, so something will have to be dropped */
+
+ /* If the new pointer is greater than the current max, drop it */
+ if (heap->gt(p, ptrs[0]))
+ return p;
+
+ /* Replace the current max and heapify */
+ res = ptrs[0];
+ ptrs[0] = p;
+ pos = 0;
+
+ while (1) {
+ int left = 2 * pos + 1;
+ int right = 2 * pos + 2;
+ int largest = pos;
+ if (left < heap->size && heap->gt(ptrs[left], p))
+ largest = left;
+ if (right < heap->size && heap->gt(ptrs[right], ptrs[largest]))
+ largest = right;
+ if (largest == pos)
+ break;
+ /* Push p down the heap one level and bump one up */
+ ptrs[pos] = ptrs[largest];
+ ptrs[largest] = p;
+ pos = largest;
+ }
+ return res;
+}