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Merge branch 'semaphore' of git://git.kernel.org/pub/scm/linux/kernel/git/willy/misc 

* 'semaphore' of git://git.kernel.org/pub/scm/linux/kernel/git/willy/misc:
  Remove __DECLARE_SEMAPHORE_GENERIC
  Remove asm/semaphore.h
  Remove use of asm/semaphore.h
  Add missing semaphore.h includes
  Remove mention of semaphores from kernel-locking
This commit is contained in:
Linus Torvalds 2008-07-24 12:24:40 -07:00
parent 3fde80e94c b552068999
commit 7540081c6b
29 changed files with 30 additions and 68 deletions
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57
Documentation/DocBook/kernel-locking.tmpl
View File

@ -219,10 +219,10 @@
</para>
<sect1 id="lock-intro">
<title>Three Main Types of Kernel Locks: Spinlocks, Mutexes and Semaphores</title>
<title>Two Main Types of Kernel Locks: Spinlocks and Mutexes</title>
<para>
There are three main types of kernel locks. The fundamental type
There are two main types of kernel locks. The fundamental type
is the spinlock
(<filename class="headerfile">include/asm/spinlock.h</filename>),
which is a very simple single-holder lock: if you can't get the
@ -239,14 +239,6 @@
can't sleep (see <xref linkend="sleeping-things"/>), and so have to
use a spinlock instead.
</para>
<para>
The third type is a semaphore
(<filename class="headerfile">include/linux/semaphore.h</filename>): it
can have more than one holder at any time (the number decided at
initialization time), although it is most commonly used as a
single-holder lock (a mutex). If you can't get a semaphore, your
task will be suspended and later on woken up - just like for mutexes.
</para>
<para>
Neither type of lock is recursive: see
<xref linkend="deadlock"/>.
@ -278,7 +270,7 @@
</para>
<para>
Semaphores still exist, because they are required for
Mutexes still exist, because they are required for
synchronization between <firstterm linkend="gloss-usercontext">user
contexts</firstterm>, as we will see below.
</para>
@ -289,18 +281,17 @@
<para>
If you have a data structure which is only ever accessed from
user context, then you can use a simple semaphore
(<filename>linux/linux/semaphore.h</filename>) to protect it. This
is the most trivial case: you initialize the semaphore to the number
of resources available (usually 1), and call
<function>down_interruptible()</function> to grab the semaphore, and
<function>up()</function> to release it. There is also a
<function>down()</function>, which should be avoided, because it
user context, then you can use a simple mutex
(<filename>include/linux/mutex.h</filename>) to protect it. This
is the most trivial case: you initialize the mutex. Then you can
call <function>mutex_lock_interruptible()</function> to grab the mutex,
and <function>mutex_unlock()</function> to release it. There is also a
<function>mutex_lock()</function>, which should be avoided, because it
will not return if a signal is received.
</para>
<para>
Example: <filename>linux/net/core/netfilter.c</filename> allows
Example: <filename>net/netfilter/nf_sockopt.c</filename> allows
registration of new <function>setsockopt()</function> and
<function>getsockopt()</function> calls, with
<function>nf_register_sockopt()</function>. Registration and
@ -515,7 +506,7 @@
<listitem>
<para>
If you are in a process context (any syscall) and want to
lock other process out, use a semaphore. You can take a semaphore
lock other process out, use a mutex. You can take a mutex
and sleep (<function>copy_from_user*(</function> or
<function>kmalloc(x,GFP_KERNEL)</function>).
</para>
@ -662,7 +653,7 @@
<entry>SLBH</entry>
<entry>SLBH</entry>
<entry>SLBH</entry>
<entry>DI</entry>
<entry>MLI</entry>
<entry>None</entry>
</row>
@ -692,8 +683,8 @@
<entry>spin_lock_bh</entry>
</row>
<row>
<entry>DI</entry>
<entry>down_interruptible</entry>
<entry>MLI</entry>
<entry>mutex_lock_interruptible</entry>
</row>
</tbody>
@ -1310,7 +1301,7 @@ as Alan Cox says, <quote>Lock data, not code</quote>.
<para>
There is a coding bug where a piece of code tries to grab a
spinlock twice: it will spin forever, waiting for the lock to
be released (spinlocks, rwlocks and semaphores are not
be released (spinlocks, rwlocks and mutexes are not
recursive in Linux). This is trivial to diagnose: not a
stay-up-five-nights-talk-to-fluffy-code-bunnies kind of
problem.
@ -1335,7 +1326,7 @@ as Alan Cox says, <quote>Lock data, not code</quote>.
<para>
This complete lockup is easy to diagnose: on SMP boxes the
watchdog timer or compiling with <symbol>DEBUG_SPINLOCKS</symbol> set
watchdog timer or compiling with <symbol>DEBUG_SPINLOCK</symbol> set
(<filename>include/linux/spinlock.h</filename>) will show this up
immediately when it happens.
</para>
@ -1558,7 +1549,7 @@ the amount of locking which needs to be done.
<title>Read/Write Lock Variants</title>
<para>
Both spinlocks and semaphores have read/write variants:
Both spinlocks and mutexes have read/write variants:
<type>rwlock_t</type> and <structname>struct rw_semaphore</structname>.
These divide users into two classes: the readers and the writers. If
you are only reading the data, you can get a read lock, but to write to
@ -1681,7 +1672,7 @@ the amount of locking which needs to be done.
#include &lt;linux/slab.h&gt;
#include &lt;linux/string.h&gt;
+#include &lt;linux/rcupdate.h&gt;
#include &lt;linux/semaphore.h&gt;
#include &lt;linux/mutex.h&gt;
#include &lt;asm/errno.h&gt;
struct object
@ -1913,7 +1904,7 @@ machines due to caching.
</listitem>
<listitem>
<para>
<function> put_user()</function>
<function>put_user()</function>
</para>
</listitem>
</itemizedlist>
@ -1927,13 +1918,13 @@ machines due to caching.
<listitem>
<para>
<function>down_interruptible()</function> and
<function>down()</function>
<function>mutex_lock_interruptible()</function> and
<function>mutex_lock()</function>
</para>
<para>
There is a <function>down_trylock()</function> which can be
There is a <function>mutex_trylock()</function> which can be
used inside interrupt context, as it will not sleep.
<function>up()</function> will also never sleep.
<function>mutex_unlock()</function> will also never sleep.
</para>
</listitem>
</itemizedlist>
@ -2023,7 +2014,7 @@ machines due to caching.
<para>
Prior to 2.5, or when <symbol>CONFIG_PREEMPT</symbol> is
unset, processes in user context inside the kernel would not
preempt each other (ie. you had that CPU until you have it up,
preempt each other (ie. you had that CPU until you gave it up,
except for interrupts). With the addition of
<symbol>CONFIG_PREEMPT</symbol> in 2.5.4, this changed: when
in user context, higher priority tasks can "cut in": spinlocks

8
Documentation/feature-removal-schedule.txt
View File

@ -300,14 +300,6 @@ Who: ocfs2-devel@oss.oracle.com
---------------------------
What: asm/semaphore.h
When: 2.6.26
Why: Implementation became generic; users should now include
linux/semaphore.h instead.
Who: Matthew Wilcox <willy@linux.intel.com>
---------------------------
What: SCTP_GET_PEER_ADDRS_NUM_OLD, SCTP_GET_PEER_ADDRS_OLD,
SCTP_GET_LOCAL_ADDRS_NUM_OLD, SCTP_GET_LOCAL_ADDRS_OLD
When: June 2009

2
arch/arm/mach-ns9xxx/clock.c
View File

@ -14,8 +14,8 @@
#include <linux/clk.h>
#include <linux/string.h>
#include <linux/platform_device.h>
#include <linux/semaphore.h>
#include <asm/semaphore.h>
#include "clock.h"
static LIST_HEAD(clocks);

1
drivers/input/keyboard/hil_kbd.c
View File

@ -37,6 +37,7 @@
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/semaphore.h>
#include <linux/slab.h>
#include <linux/pci_ids.h>

1
drivers/input/misc/hp_sdc_rtc.c
View File

@ -44,6 +44,7 @@
#include <linux/proc_fs.h>
#include <linux/poll.h>
#include <linux/rtc.h>
#include <linux/semaphore.h>
MODULE_AUTHOR("Brian S. Julin <bri@calyx.com>");
MODULE_DESCRIPTION("HP i8042 SDC + MSM-58321 RTC Driver");

1
drivers/input/serio/hp_sdc.c
View File

@ -67,6 +67,7 @@
#include <linux/module.h>
#include <linux/ioport.h>
#include <linux/time.h>
#include <linux/semaphore.h>
#include <linux/slab.h>
#include <linux/hil.h>
#include <linux/semaphore.h>

1
include/asm-alpha/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

1
include/asm-arm/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

1
include/asm-avr32/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

1
include/asm-blackfin/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

1
include/asm-cris/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

1
include/asm-frv/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

1
include/asm-h8300/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

1
include/asm-ia64/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

1
include/asm-m32r/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

1
include/asm-m68k/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

1
include/asm-m68knommu/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

1
include/asm-mips/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

1
include/asm-mn10300/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

1
include/asm-parisc/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

1
include/asm-powerpc/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

1
include/asm-s390/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

1
include/asm-sh/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

1
include/asm-sparc/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

1
include/asm-sparc64/semaphore.h
View File

@ -1 +0,0 @@
#include <asm-sparc/semaphore.h>

1
include/asm-um/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

1
include/asm-x86/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

1
include/asm-xtensa/semaphore.h
View File

@ -1 +0,0 @@
#include <linux/semaphore.h>

6
include/linux/semaphore.h
View File

@ -26,10 +26,8 @@ struct semaphore {
.wait_list = LIST_HEAD_INIT((name).wait_list), \
}
#define __DECLARE_SEMAPHORE_GENERIC(name, count) \
struct semaphore name = __SEMAPHORE_INITIALIZER(name, count)
#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name, 1)
#define DECLARE_MUTEX(name) \
struct semaphore name = __SEMAPHORE_INITIALIZER(name, 1)
static inline void sema_init(struct semaphore *sem, int val)
{