Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 7540081c authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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
parents 3fde80e9 b5520689

Documentation/DocBook/kernel-locking.tmpl

+24 −33
Original line number Original line Diff line number Diff line
@@ -219,10 +219,10 @@ 
   </para>

   </para>





   <sect1 id="lock-intro">

   <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>

   <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 

     is the spinlock 

     (<filename class="headerfile">include/asm/spinlock.h</filename>),

     (<filename class="headerfile">include/asm/spinlock.h</filename>),

     which is a very simple single-holder lock: if you can't get the 

     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

     can't sleep (see <xref linkend="sleeping-things"/>), and so have to

     use a spinlock instead.

     use a spinlock instead.

   </para>

   </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>

   <para>

     Neither type of lock is recursive: see

     Neither type of lock is recursive: see

     <xref linkend="deadlock"/>.

     <xref linkend="deadlock"/>.
@@ -278,7 +270,7 @@ 
    </para>

    </para>





    <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 

      synchronization between <firstterm linkend="gloss-usercontext">user 

      contexts</firstterm>, as we will see below.

      contexts</firstterm>, as we will see below.

    </para>

    </para>
@@ -289,18 +281,17 @@ 




     <para>

     <para>

       If you have a data structure which is only ever accessed from

       If you have a data structure which is only ever accessed from

       user context, then you can use a simple semaphore

       user context, then you can use a simple mutex

       (<filename>linux/linux/semaphore.h</filename>) to protect it.  This

       (<filename>include/linux/mutex.h</filename>) to protect it.  This

       is the most trivial case: you initialize the semaphore to the number 

       is the most trivial case: you initialize the mutex.  Then you can

       of resources available (usually 1), and call

       call <function>mutex_lock_interruptible()</function> to grab the mutex,

       <function>down_interruptible()</function> to grab the semaphore, and 

       and <function>mutex_unlock()</function> to release it.  There is also a 

       <function>up()</function> to release it.  There is also a 

       <function>mutex_lock()</function>, which should be avoided, because it 

       <function>down()</function>, which should be avoided, because it 

       will not return if a signal is received.

       will not return if a signal is received.

     </para>

     </para>





     <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 

       registration of new <function>setsockopt()</function> and 

       <function>getsockopt()</function> calls, with

       <function>getsockopt()</function> calls, with

       <function>nf_register_sockopt()</function>.  Registration and 

       <function>nf_register_sockopt()</function>.  Registration and
@@ -515,7 +506,7 @@ 
      <listitem>

      <listitem>

	<para>

	<para>

          If you are in a process context (any syscall) and want to

          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

	and sleep (<function>copy_from_user*(</function> or

	<function>kmalloc(x,GFP_KERNEL)</function>).

	<function>kmalloc(x,GFP_KERNEL)</function>).

      </para>

      </para>
@@ -662,7 +653,7 @@ 
<entry>SLBH</entry>

<entry>SLBH</entry>

<entry>SLBH</entry>

<entry>SLBH</entry>

<entry>SLBH</entry>

<entry>SLBH</entry>

<entry>DI</entry>

<entry>MLI</entry>

<entry>None</entry>

<entry>None</entry>

</row>

</row>
@@ -692,8 +683,8 @@ 
<entry>spin_lock_bh</entry>

<entry>spin_lock_bh</entry>

</row>

</row>

<row>

<row>

<entry>DI</entry>

<entry>MLI</entry>

<entry>down_interruptible</entry>

<entry>mutex_lock_interruptible</entry>

</row>

</row>





</tbody>

</tbody>
@@ -1310,7 +1301,7 @@ as Alan Cox says, <quote>Lock data, not code</quote>. 
    <para>

    <para>

      There is a coding bug where a piece of code tries to grab a

      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

      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

      recursive in Linux).  This is trivial to diagnose: not a

      stay-up-five-nights-talk-to-fluffy-code-bunnies kind of

      stay-up-five-nights-talk-to-fluffy-code-bunnies kind of

      problem.

      problem.
@@ -1335,7 +1326,7 @@ as Alan Cox says, <quote>Lock data, not code</quote>. 




    <para>

    <para>

      This complete lockup is easy to diagnose: on SMP boxes the

      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 

      (<filename>include/linux/spinlock.h</filename>) will show this up 

      immediately when it happens.

      immediately when it happens.

    </para>

    </para>
@@ -1558,7 +1549,7 @@ the amount of locking which needs to be done. 
   <title>Read/Write Lock Variants</title>

   <title>Read/Write Lock Variants</title>





   <para>

   <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>.

      <type>rwlock_t</type> and <structname>struct rw_semaphore</structname>.

      These divide users into two classes: the readers and the writers.  If

      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

      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/slab.h&gt;

 #include &lt;linux/string.h&gt;

 #include &lt;linux/string.h&gt;

+#include &lt;linux/rcupdate.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;

 #include &lt;asm/errno.h&gt;





 struct object

 struct object
@@ -1927,13 +1918,13 @@ machines due to caching. 




     <listitem>

     <listitem>

      <para>

      <para>

      <function>down_interruptible()</function> and

      <function>mutex_lock_interruptible()</function> and

      <function>down()</function>

      <function>mutex_lock()</function>

      </para>

      </para>

      <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.

       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>

      </para>

     </listitem>

     </listitem>

    </itemizedlist>

    </itemizedlist>
@@ -2023,7 +2014,7 @@ machines due to caching. 
      <para>

      <para>

        Prior to 2.5, or when <symbol>CONFIG_PREEMPT</symbol> is

        Prior to 2.5, or when <symbol>CONFIG_PREEMPT</symbol> is

        unset, processes in user context inside the kernel would not

        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

        except for interrupts).  With the addition of

        <symbol>CONFIG_PREEMPT</symbol> in 2.5.4, this changed: when

        <symbol>CONFIG_PREEMPT</symbol> in 2.5.4, this changed: when

        in user context, higher priority tasks can "cut in": spinlocks

        in user context, higher priority tasks can "cut in": spinlocks

Documentation/feature-removal-schedule.txt

+0 −8
Original line number Original line Diff line number Diff line
@@ -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,

What:	SCTP_GET_PEER_ADDRS_NUM_OLD, SCTP_GET_PEER_ADDRS_OLD,

	SCTP_GET_LOCAL_ADDRS_NUM_OLD, SCTP_GET_LOCAL_ADDRS_OLD

	SCTP_GET_LOCAL_ADDRS_NUM_OLD, SCTP_GET_LOCAL_ADDRS_OLD

When: 	June 2009

When: 	June 2009

arch/arm/mach-ns9xxx/clock.c

+1 −1
Original line number Original line Diff line number Diff line
@@ -14,8 +14,8 @@ 
#include <linux/clk.h>

#include <linux/clk.h>

#include <linux/string.h>

#include <linux/string.h>

#include <linux/platform_device.h>

#include <linux/platform_device.h>

#include <linux/semaphore.h>





#include <asm/semaphore.h>

#include "clock.h"

#include "clock.h"





static LIST_HEAD(clocks);

static LIST_HEAD(clocks);

drivers/input/keyboard/hil_kbd.c

+1 −0
Original line number Original line Diff line number Diff line
@@ -37,6 +37,7 @@ 
#include <linux/kernel.h>

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/module.h>

#include <linux/init.h>

#include <linux/init.h>

#include <linux/semaphore.h>

#include <linux/slab.h>

#include <linux/slab.h>

#include <linux/pci_ids.h>

#include <linux/pci_ids.h>

drivers/input/misc/hp_sdc_rtc.c

+1 −0
Original line number Original line Diff line number Diff line
@@ -44,6 +44,7 @@ 
#include <linux/proc_fs.h>

#include <linux/proc_fs.h>

#include <linux/poll.h>

#include <linux/poll.h>

#include <linux/rtc.h>

#include <linux/rtc.h>

#include <linux/semaphore.h>





MODULE_AUTHOR("Brian S. Julin <bri@calyx.com>");

MODULE_AUTHOR("Brian S. Julin <bri@calyx.com>");

MODULE_DESCRIPTION("HP i8042 SDC + MSM-58321 RTC Driver");

MODULE_DESCRIPTION("HP i8042 SDC + MSM-58321 RTC Driver");