stop_machine: add ALL_CPUS option

-allow stop_mahcine_run() to call a function on all cpus. Calling
 stop_machine_run() with a 'ALL_CPUS' invokes this new behavior.
 stop_machine_run() proceeds as normal until the calling cpu has
 invoked 'fn'. Then, we tell all the other cpus to call 'fn'.

Signed-off-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
CC: Adrian Bunk <bunk@stusta.de>
CC: Andi Kleen <andi@firstfloor.org>
CC: Alexey Dobriyan <adobriyan@gmail.com>
CC: Christoph Hellwig <hch@infradead.org>
CC: mingo@elte.hu
CC: akpm@osdl.org

1 files changed, 7 insertions, 1 deletions

diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h
index 5bfc553bdb21..18af011c13af 100644
--- a/include/linux/stop_machine.h
+++ b/include/linux/stop_machine.h
@@ -8,11 +8,17 @@
 #include <asm/system.h>
 
 #if defined(CONFIG_STOP_MACHINE) && defined(CONFIG_SMP)
+
+#define ALL_CPUS ~0U
+
 /**
  * stop_machine_run: 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.
+ * @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
  *
  * Description: This causes a thread to be scheduled on every other cpu,
  * each of which disables interrupts, and finally interrupts are disabled