Simplify stop_machine

stop_machine creates a kthread which creates kernel threads.  We can
create those threads directly and simplify things a little.  Some care
must be taken with CPU hotunplug, which has special needs, but that code
seems more robust than it was in the past.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>

1 files changed, 8 insertions, 12 deletions

diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h
index 18af011c13af..36c2c7284eb3 100644
--- a/include/linux/stop_machine.h
+++ b/include/linux/stop_machine.h
@@ -17,13 +17,12 @@
  * @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() first on the calling cpu, and then
- *       concurrently on all the other cpus
+ *       if @cpu == ALL_CPUS, run @fn() on every online CPU.
  *
- * Description: This causes a thread to be scheduled on every other cpu,
- * each of which disables interrupts, and finally interrupts are disabled
- * on the current CPU.  The result is that noone is holding a spinlock
- * or inside any other preempt-disabled region when @fn() runs.
+ * Description: This causes a thread to be scheduled on every cpu,
+ * each of which disables interrupts.  The result is that noone is
+ * holding a spinlock or inside any other preempt-disabled region when
+ * @fn() runs.
  *
  * This can be thought of as a very heavy write lock, equivalent to
  * grabbing every spinlock in the kernel. */
@@ -35,13 +34,10 @@ int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu);
  * @data: the data ptr for the @fn
  * @cpu: the cpu to run @fn on (or any, if @cpu == NR_CPUS.
  *
- * Description: This is a special version of the above, which returns the
- * thread which has run @fn(): kthread_stop will return the return value
- * of @fn().  Used by hotplug 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.
  */
-struct task_struct *__stop_machine_run(int (*fn)(void *), void *data,
-				       unsigned int cpu);
-
+int __stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu);
 #else
 
 static inline int stop_machine_run(int (*fn)(void *), void *data,