cpumask: introduce new API, without changing anything

Impact: introduce new APIs

We want to deprecate cpumasks on the stack, as we are headed for
gynormous numbers of CPUs.  Eventually, we want to head towards an
undefined 'struct cpumask' so they can never be declared on stack.

1) New cpumask functions which take pointers instead of copies.
   (cpus_* -> cpumask_*)

2) Several new helpers to reduce requirements for temporary cpumasks
   (cpumask_first_and, cpumask_next_and, cpumask_any_and)

3) Helpers for declaring cpumasks on or offstack for large NR_CPUS
   (cpumask_var_t, alloc_cpumask_var and free_cpumask_var)

4) 'struct cpumask' for explicitness and to mark new-style code.

5) Make iterator functions stop at nr_cpu_ids (a runtime constant),
   not NR_CPUS for time efficiency and for smaller dynamic allocations
   in future.

6) cpumask_copy() so we can allocate less than a full cpumask eventually
   (for alloc_cpumask_var), and so we can eliminate the 'struct cpumask'
   definition eventually.

7) work_on_cpu() helper for doing task on a CPU, rather than saving old
   cpumask for current thread and manipulating it.

8) smp_call_function_many() which is smp_call_function_mask() except
   taking a cpumask pointer.

Note that this patch simply introduces the new functions and leaves
the obsolescent ones in place.  This is to simplify the transition
patches.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 73 insertions, 0 deletions

diff --git a/lib/cpumask.c b/lib/cpumask.c
index 5f97dc25ef9..5ceb4211c83 100644
--- a/lib/cpumask.c
+++ b/lib/cpumask.c
@@ -2,6 +2,7 @@
 #include <linux/bitops.h>
 #include <linux/cpumask.h>
 #include <linux/module.h>
+#include <linux/bootmem.h>
 
 int __first_cpu(const cpumask_t *srcp)
 {
@@ -35,3 +36,75 @@ int __any_online_cpu(const cpumask_t *mask)
         return cpu;
 }
 EXPORT_SYMBOL(__any_online_cpu);
+
+/**
+ * cpumask_next_and - get the next cpu in *src1p & *src2p
+ * @n: the cpu prior to the place to search (ie. return will be > @n)
+ * @src1p: the first cpumask pointer
+ * @src2p: the second cpumask pointer
+ *
+ * Returns >= nr_cpu_ids if no further cpus set in both.
+ */
+int cpumask_next_and(int n, const struct cpumask *src1p,
+                     const struct cpumask *src2p)
+{
+        while ((n = cpumask_next(n, src1p)) < nr_cpu_ids)
+                if (cpumask_test_cpu(n, src2p))
+                        break;
+        return n;
+}
+EXPORT_SYMBOL(cpumask_next_and);
+
+/**
+ * cpumask_any_but - return a "random" in a cpumask, but not this one.
+ * @mask: the cpumask to search
+ * @cpu: the cpu to ignore.
+ *
+ * Often used to find any cpu but smp_processor_id() in a mask.
+ * Returns >= nr_cpu_ids if no cpus set.
+ */
+int cpumask_any_but(const struct cpumask *mask, unsigned int cpu)
+{
+        unsigned int i;
+
+        for_each_cpu(i, mask)
+                if (i != cpu)
+                        break;
+        return i;
+}
+
+/* These are not inline because of header tangles. */
+#ifdef CONFIG_CPUMASK_OFFSTACK
+bool alloc_cpumask_var(cpumask_var_t *mask, gfp_t flags)
+{
+        if (likely(slab_is_available()))
+                *mask = kmalloc(cpumask_size(), flags);
+        else {
+#ifdef CONFIG_DEBUG_PER_CPU_MAPS
+                printk(KERN_ERR
+                        "=> alloc_cpumask_var: kmalloc not available!\n");
+                dump_stack();
+#endif
+                *mask = NULL;
+        }
+#ifdef CONFIG_DEBUG_PER_CPU_MAPS
+        if (!*mask) {
+                printk(KERN_ERR "=> alloc_cpumask_var: failed!\n");
+                dump_stack();
+        }
+#endif
+        return *mask != NULL;
+}
+EXPORT_SYMBOL(alloc_cpumask_var);
+
+void __init alloc_bootmem_cpumask_var(cpumask_var_t *mask)
+{
+        *mask = alloc_bootmem(cpumask_size());
+}
+
+void free_cpumask_var(cpumask_var_t mask)
+{
+        kfree(mask);
+}
+EXPORT_SYMBOL(free_cpumask_var);
+#endif