Merge branch 'mauro-books' into docs-next
Merge Mauro's massive patch series creating the process and admin-guide
books. I think there's a lot of stuff to clean up here, but there's no
point in holding things up for that.
Mauro sez:
This patch series continues the efforts of converting the Linux Kernel
documentation to Sphinx.
It contains text to ReST conversion of several files under Documentation,
and a few ones under the main dir (README, REPORTING-BUGS).
All patches on this series can be found on my development tree:
https://git.linuxtv.org/mchehab/experimental.git/log/?h=lkml-books-v2
The Kernel docs html output after this series can be seen at:
https://mchehab.fedorapeople.org/kernel_docs/
diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt
index dd68821..d02e8a4 100644
--- a/Documentation/cpu-hotplug.txt
+++ b/Documentation/cpu-hotplug.txt
@@ -84,9 +84,9 @@
upfront can save some boot time memory. See below for how we use heuristics
in x86_64 case to keep this under check.
-cpu_online_mask: Bitmap of all CPUs currently online. Its set in __cpu_up()
-after a cpu is available for kernel scheduling and ready to receive
-interrupts from devices. Its cleared when a cpu is brought down using
+cpu_online_mask: Bitmap of all CPUs currently online. It's set in __cpu_up()
+after a CPU is available for kernel scheduling and ready to receive
+interrupts from devices. It's cleared when a CPU is brought down using
__cpu_disable(), before which all OS services including interrupts are
migrated to another target CPU.
@@ -181,7 +181,7 @@
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.
-Q: How do i logically offline a CPU?
+Q: How do I logically offline a CPU?
A: Do the following.
#echo 0 > /sys/devices/system/cpu/cpuX/online
@@ -191,15 +191,15 @@
#cat /proc/interrupts
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.
+the state as 0 when a CPU is offline and 1 when it's online.
#To display the current cpu state.
#cat /sys/devices/system/cpu/cpuX/online
-Q: Why can't i remove CPU0 on some systems?
+Q: Why can't I remove CPU0 on some systems?
A: Some architectures may have some special dependency on a certain CPU.
-For e.g in IA64 platforms we have ability to sent platform interrupts to the
+For e.g in IA64 platforms we have ability to send platform interrupts to the
OS. a.k.a Corrected Platform Error Interrupts (CPEI). In current ACPI
specifications, we didn't have a way to change the target CPU. Hence if the
current ACPI version doesn't support such re-direction, we disable that CPU
@@ -231,7 +231,7 @@
--Fenghua Yu <fenghua.yu@intel.com>
-Q: How do i find out if a particular CPU is not removable?
+Q: How do I find out if a particular CPU is not removable?
A: Depending on the implementation, some architectures may show this by the
absence of the "online" file. This is done if it can be determined ahead of
time that this CPU cannot be removed.
@@ -250,7 +250,7 @@
- All processes are migrated away from this outgoing CPU to new CPUs.
The new CPU is chosen from each process' current cpuset, which may be
a subset of all online CPUs.
-- All interrupts targeted to this CPU is migrated to a new CPU
+- All interrupts targeted to this CPU are migrated to a new CPU
- timers/bottom half/task lets are also migrated to a new CPU
- Once all services are migrated, kernel calls an arch specific routine
__cpu_disable() to perform arch specific cleanup.
@@ -259,10 +259,10 @@
CPU is being offlined).
"It is expected that each service cleans up when the CPU_DOWN_PREPARE
- notifier is called, when CPU_DEAD is called its expected there is nothing
+ notifier is called, when CPU_DEAD is called it's expected there is nothing
running on behalf of this CPU that was offlined"
-Q: If i have some kernel code that needs to be aware of CPU arrival and
+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.
@@ -311,7 +311,7 @@
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
+ If you need to perform some action for each CPU already in the system, then
do this:
for_each_online_cpu(i) {
@@ -363,8 +363,8 @@
callbacks as well as initialize the already online CPUs.
-Q: If i would like to develop cpu hotplug support for a new architecture,
- what do i need at a minimum?
+Q: If I would like to develop CPU hotplug support for a new architecture,
+ what do I need at a minimum?
A: The following are what is required for CPU hotplug infrastructure to work
correctly.
@@ -382,8 +382,8 @@
per_cpu state to be set, to ensure the processor
dead routine is called to be sure positively.
-Q: I need to ensure that a particular cpu is not removed when there is some
- work specific to this cpu is in progress.
+Q: I need to ensure that a particular CPU is not removed when there is some
+ work specific to this CPU in progress.
A: There are two ways. If your code can be run in interrupt context, use
smp_call_function_single(), otherwise use work_on_cpu(). Note that
work_on_cpu() is slow, and can fail due to out of memory:
diff --git a/Documentation/ko_KR/memory-barriers.txt b/Documentation/ko_KR/memory-barriers.txt
index 34d3d38..a3228a6 100644
--- a/Documentation/ko_KR/memory-barriers.txt
+++ b/Documentation/ko_KR/memory-barriers.txt
@@ -823,6 +823,38 @@
오퍼레이션을 위한 코드를 정말로 만들도록 하지만, 컴파일러가 그렇게 만들어진
코드의 수행 결과를 사용하도록 강제하지는 않습니다.
+또한, 컨트롤 의존성은 if 문의 then 절과 else 절에 대해서만 적용됩니다. 상세히
+말해서, 컨트롤 의존성은 if 문을 뒤따르는 코드에는 적용되지 않습니다:
+
+ q = READ_ONCE(a);
+ if (q) {
+ WRITE_ONCE(b, p);
+ } else {
+ WRITE_ONCE(b, r);
+ }
+ WRITE_ONCE(c, 1); /* BUG: No ordering against the read from "a". */
+
+컴파일러는 volatile 타입에 대한 액세스를 재배치 할 수 없고 이 조건 하의 "b"
+로의 쓰기를 재배치 할 수 없기 때문에 여기에 순서 규칙이 존재한다고 주장하고
+싶을 겁니다. 불행히도 이 경우에, 컴파일러는 다음의 가상의 pseudo-assembly 언어
+코드처럼 "b" 로의 두개의 쓰기 오퍼레이션을 conditional-move 인스트럭션으로
+번역할 수 있습니다:
+
+ ld r1,a
+ ld r2,p
+ ld r3,r
+ cmp r1,$0
+ cmov,ne r4,r2
+ cmov,eq r4,r3
+ st r4,b
+ st $1,c
+
+완화된 순서 규칙의 CPU 는 "a" 로부터의 로드와 "c" 로의 스토어 사이에 어떤
+종류의 의존성도 갖지 않을 겁니다. 이 컨트롤 의존성은 두개의 cmov 인스트럭션과
+거기에 의존하는 스토어 에게만 적용될 겁니다. 짧게 말하자면, 컨트롤 의존성은
+주어진 if 문의 then 절과 else 절에게만 (그리고 이 두 절 내에서 호출되는
+함수들에게까지) 적용되지, 이 if 문을 뒤따르는 코드에는 적용되지 않습니다.
+
마지막으로, 컨트롤 의존성은 이행성 (transitivity) 을 제공하지 -않습니다-. 이건
x 와 y 가 둘 다 0 이라는 초기값을 가졌다는 가정 하의 두개의 예제로
보이겠습니다:
@@ -883,6 +915,10 @@
의존성이 사라지지 않게 하는데 도움을 줄 수 있습니다. 더 많은 정보를
위해선 "컴파일러 배리어" 섹션을 참고하시기 바랍니다.
+ (*) 컨트롤 의존성은 컨트롤 의존성을 갖는 if 문의 then 절과 else 절과 이 두 절
+ 내에서 호출되는 함수들에만 적용됩니다. 컨트롤 의존성은 컨트롤 의존성을
+ 갖는 if 문을 뒤따르는 코드에는 적용되지 -않습니다-.
+
(*) 컨트롤 의존성은 보통 다른 타입의 배리어들과 짝을 맞춰 사용됩니다.
(*) 컨트롤 의존성은 이행성을 제공하지 -않습니다-. 이행성이 필요하다면,