[PATCH] doc: fixing cpu-hotplug documentation

Fixing cpu-hotplug documentation as follows:

 - moving confusing asterisk on additional_cpus descrition
 - fixing some typos
 - unifying indentation for source code and command line example

Signed-off-by: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt
index bc107cb..4868c34 100644 (file)
--- a/Documentation/cpu-hotplug.txt
+++ b/Documentation/cpu-hotplug.txt
@@ -46,7 +46,7 @@ maxcpus=n    Restrict boot time cpus to n. Say if you have 4 cpus, using
              maxcpus=2 will only boot 2. You can choose to bring the
              other cpus later online, read FAQ's for more info.
 
-additional_cpus*=n     Use this to limit hotpluggable cpus. This option sets
+additional_cpus=n (*)  Use this to limit hotpluggable cpus. This option sets
                        cpu_possible_map = cpu_present_map + additional_cpus
 
 (*) Option valid only for following architectures
@@ -101,15 +101,15 @@ cpu_possible_map/for_each_possible_cpu() to iterate.
 
 Never use anything other than cpumask_t to represent bitmap of CPUs.
 
-#include <linux/cpumask.h>
+       #include <linux/cpumask.h>
 
-for_each_possible_cpu     - Iterate over cpu_possible_map
-for_each_online_cpu       - Iterate over cpu_online_map
-for_each_present_cpu      - Iterate over cpu_present_map
-for_each_cpu_mask(x,mask) - Iterate over some random collection of cpu mask.
+       for_each_possible_cpu     - Iterate over cpu_possible_map
+       for_each_online_cpu       - Iterate over cpu_online_map
+       for_each_present_cpu      - Iterate over cpu_present_map
+       for_each_cpu_mask(x,mask) - Iterate over some random collection of cpu mask.
 
-#include <linux/cpu.h>
-lock_cpu_hotplug() and unlock_cpu_hotplug():
+       #include <linux/cpu.h>
+       lock_cpu_hotplug() and unlock_cpu_hotplug():
 
 The above calls are used to inhibit cpu hotplug operations. While holding the
 cpucontrol mutex, cpu_online_map will not change. If you merely need to avoid
@@ -120,7 +120,7 @@ will work as long as stop_machine_run() is used to take a cpu down.
 
 CPU Hotplug - Frequently Asked Questions.
 
-Q: How to i enable my kernel to support CPU hotplug?
+Q: How to enable my kernel to support CPU hotplug?
 A: When doing make defconfig, Enable CPU hotplug support
 
    "Processor type and Features" -> Support for Hotpluggable CPUs
@@ -141,39 +141,39 @@ A: You should now notice an entry in sysfs.
 Check if sysfs is mounted, using the "mount" command. You should notice
 an entry as shown below in the output.
 
-....
-none on /sys type sysfs (rw)
-....
+       ....
+       none on /sys type sysfs (rw)
+       ....
 
-if this is not mounted, do the following.
+If this is not mounted, do the following.
 
-#mkdir /sysfs
-#mount -t sysfs sys /sys
+        #mkdir /sysfs
+       #mount -t sysfs sys /sys
 
-now you should see entries for all present cpu, the following is an example
+Now you should see entries for all present cpu, the following is an example
 in a 8-way system.
 
-#pwd
-#/sys/devices/system/cpu
-#ls -l
-total 0
-drwxr-xr-x  10 root root 0 Sep 19 07:44 .
-drwxr-xr-x  13 root root 0 Sep 19 07:45 ..
-drwxr-xr-x   3 root root 0 Sep 19 07:44 cpu0
-drwxr-xr-x   3 root root 0 Sep 19 07:44 cpu1
-drwxr-xr-x   3 root root 0 Sep 19 07:44 cpu2
-drwxr-xr-x   3 root root 0 Sep 19 07:44 cpu3
-drwxr-xr-x   3 root root 0 Sep 19 07:44 cpu4
-drwxr-xr-x   3 root root 0 Sep 19 07:44 cpu5
-drwxr-xr-x   3 root root 0 Sep 19 07:44 cpu6
-drwxr-xr-x   3 root root 0 Sep 19 07:48 cpu7
+       #pwd
+       #/sys/devices/system/cpu
+       #ls -l
+       total 0
+       drwxr-xr-x  10 root root 0 Sep 19 07:44 .
+       drwxr-xr-x  13 root root 0 Sep 19 07:45 ..
+       drwxr-xr-x   3 root root 0 Sep 19 07:44 cpu0
+       drwxr-xr-x   3 root root 0 Sep 19 07:44 cpu1
+       drwxr-xr-x   3 root root 0 Sep 19 07:44 cpu2
+       drwxr-xr-x   3 root root 0 Sep 19 07:44 cpu3
+       drwxr-xr-x   3 root root 0 Sep 19 07:44 cpu4
+       drwxr-xr-x   3 root root 0 Sep 19 07:44 cpu5
+       drwxr-xr-x   3 root root 0 Sep 19 07:44 cpu6
+       drwxr-xr-x   3 root root 0 Sep 19 07:48 cpu7
 
 Under each directory you would find an "online" file which is the control
 file to logically online/offline a processor.
 
 Q: Does hot-add/hot-remove refer to physical add/remove of cpus?
 A: The usage of hot-add/remove may not be very consistently used in the code.
-CONFIG_CPU_HOTPLUG enables logical online/offline capability in the kernel.
+CONFIG_HOTPLUG_CPU enables logical online/offline capability in the kernel.
 To support physical addition/removal, one would need some BIOS hooks and
 the platform should have something like an attention button in PCI hotplug.
 CONFIG_ACPI_HOTPLUG_CPU enables ACPI support for physical add/remove of CPUs.
@@ -181,17 +181,17 @@ CONFIG_ACPI_HOTPLUG_CPU enables ACPI support for physical add/remove of CPUs.
 Q: How do i logically offline a CPU?
 A: Do the following.
 
-#echo 0 > /sys/devices/system/cpu/cpuX/online
+       #echo 0 > /sys/devices/system/cpu/cpuX/online
 
-once the logical offline is successful, check
+Once the logical offline is successful, check
 
-#cat /proc/interrupts
+       #cat /proc/interrupts
 
-you should now not see the CPU that you removed. Also online file will report
+You should now not see the CPU that you removed. Also online file will report
 the state as 0 when a cpu if offline and 1 when its online.
 
-#To display the current cpu state.
-#cat /sys/devices/system/cpu/cpuX/online
+       #To display the current cpu state.
+       #cat /sys/devices/system/cpu/cpuX/online
 
 Q: Why cant i remove CPU0 on some systems?
 A: Some architectures may have some special dependency on a certain CPU.
@@ -234,8 +234,8 @@ Q: If i have some kernel code that needs to be aware of CPU arrival and
    departure, how to i arrange for proper notification?
 A: This is what you would need in your kernel code to receive notifications.
 
-    #include <linux/cpu.h>
-    static int __cpuinit foobar_cpu_callback(struct notifier_block *nfb,
+       #include <linux/cpu.h>
+       static int __cpuinit foobar_cpu_callback(struct notifier_block *nfb,
                                            unsigned long action, void *hcpu)
        {
                unsigned int cpu = (unsigned long)hcpu;
@@ -279,10 +279,10 @@ Q: I don't see my action being called for all CPUs already up and running?
 A: Yes, CPU notifiers are called only when new CPUs are on-lined or offlined.
    If you need to perform some action for each cpu already in the system, then
 
-  for_each_online_cpu(i) {
+       for_each_online_cpu(i) {
                foobar_cpu_callback(&foobar_cpu_notifier, CPU_UP_PREPARE, i);
-               foobar_cpu_callback(&foobar-cpu_notifier, CPU_ONLINE, i);
-  }
+               foobar_cpu_callback(&foobar_cpu_notifier, CPU_ONLINE, i);
+       }
 
 Q: If i would like to develop cpu hotplug support for a new architecture,
    what do i need at a minimum?
@@ -307,38 +307,38 @@ Q: I need to ensure that a particular cpu is not removed when there is some
    work specific to this cpu is in progress.
 A: First switch the current thread context to preferred cpu
 
-   int my_func_on_cpu(int cpu)
-   {
-       cpumask_t saved_mask, new_mask = CPU_MASK_NONE;
-       int curr_cpu, err = 0;
-
-       saved_mask = current->cpus_allowed;
-       cpu_set(cpu, new_mask);
-       err = set_cpus_allowed(current, new_mask);
-
-       if (err)
-           return err;
-
-       /*
-        * If we got scheduled out just after the return from
-        * set_cpus_allowed() before running the work, this ensures
-        * we stay locked.
-        */
-       curr_cpu = get_cpu();
-
-       if (curr_cpu != cpu) {
-          err = -EAGAIN;
-           goto ret;
-       } else {
-                  /*
-           * Do work : But cant sleep, since get_cpu() disables preempt
-           */
-       }
-    ret:
-       put_cpu();
-       set_cpus_allowed(current, saved_mask);
-       return err;
-    }
+       int my_func_on_cpu(int cpu)
+       {
+               cpumask_t saved_mask, new_mask = CPU_MASK_NONE;
+               int curr_cpu, err = 0;
+
+               saved_mask = current->cpus_allowed;
+               cpu_set(cpu, new_mask);
+               err = set_cpus_allowed(current, new_mask);
+
+               if (err)
+                       return err;
+
+               /*
+                * If we got scheduled out just after the return from
+                * set_cpus_allowed() before running the work, this ensures
+                * we stay locked.
+                */
+               curr_cpu = get_cpu();
+
+               if (curr_cpu != cpu) {
+                       err = -EAGAIN;
+                       goto ret;
+               } else {
+                       /*
+                        * Do work : But cant sleep, since get_cpu() disables preempt
+                        */
+               }
+               ret:
+                       put_cpu();
+                       set_cpus_allowed(current, saved_mask);
+                       return err;
+               }
 
 
 Q: How do we determine how many CPUs are available for hotplug.