stop_machine(): stop_machine_run() changed to use cpu mask

Instead of a "cpu" arg with magic values NR_CPUS (any cpu) and ~0 (all
cpus), pass a cpumask_t.  Allow NULL for the common case (where we
don't care which CPU the function is run on): temporary cpumask_t's
are usually considered bad for stack space.

This deprecates stop_machine_run, to be removed soon when all the
callers are dead.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 24 insertions, 10 deletions

diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h
index 36c2c7284eb3..f1cb0ba6d715 100644
--- a/include/linux/stop_machine.h
+++ b/include/linux/stop_machine.h
@@ -5,19 +5,19 @@
    (and more).  So the "read" side to such a lock is anything which
    diables preeempt. */
 #include <linux/cpu.h>
+#include <linux/cpumask.h>
 #include <asm/system.h>
 
 #if defined(CONFIG_STOP_MACHINE) && defined(CONFIG_SMP)
 
+/* Deprecated, but useful for transition. */
 #define ALL_CPUS ~0U
 
 /**
- * stop_machine_run: freeze the machine on all CPUs and run this function
+ * stop_machine: freeze the machine on all CPUs and run this function
  * @fn: the function to run
  * @data: the data ptr for the @fn()
- * @cpu: if @cpu == n, run @fn() on cpu n
- *       if @cpu == NR_CPUS, run @fn() on any cpu
- *       if @cpu == ALL_CPUS, run @fn() on every online CPU.
+ * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
  *
  * Description: This causes a thread to be scheduled on every cpu,
  * each of which disables interrupts.  The result is that noone is
@@ -26,22 +26,22 @@
  *
  * This can be thought of as a very heavy write lock, equivalent to
  * grabbing every spinlock in the kernel. */
-int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu);
+int stop_machine(int (*fn)(void *), void *data, const cpumask_t *cpus);
 
 /**
- * __stop_machine_run: freeze the machine on all CPUs and run this function
+ * __stop_machine: freeze the machine on all CPUs and run this function
  * @fn: the function to run
  * @data: the data ptr for the @fn
- * @cpu: the cpu to run @fn on (or any, if @cpu == NR_CPUS.
+ * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
  *
  * Description: This is a special version of the above, which assumes cpus
  * won't come or go while it's being called.  Used by hotplug cpu.
  */
-int __stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu);
+int __stop_machine(int (*fn)(void *), void *data, const cpumask_t *cpus);
 #else
 
-static inline int stop_machine_run(int (*fn)(void *), void *data,
-                                   unsigned int cpu)
+static inline int stop_machine(int (*fn)(void *), void *data,
+                               const cpumask_t *cpus)
 {
         int ret;
         local_irq_disable();
@@ -50,4 +50,18 @@ static inline int stop_machine_run(int (*fn)(void *), void *data,
         return ret;
 }
 #endif /* CONFIG_SMP */
+
+static inline int __deprecated stop_machine_run(int (*fn)(void *), void *data,
+                                                unsigned int cpu)
+{
+        /* If they don't care which cpu fn runs on, just pick one. */
+        if (cpu == NR_CPUS)
+                return stop_machine(fn, data, NULL);
+        else if (cpu == ~0U)
+                return stop_machine(fn, data, &cpu_possible_map);
+        else {
+                cpumask_t cpus = cpumask_of_cpu(cpu);
+                return stop_machine(fn, data, &cpus);
+        }
+}
 #endif /* _LINUX_STOP_MACHINE */