BUILTIN -> MODULE : CONFIG_IOSCHED_AS

[linux-2.6.git] / Documentation / sysrq.txt

diff --git a/Documentation/sysrq.txt b/Documentation/sysrq.txt
index d298eaf..ad0bedf 100644 (file)
--- a/Documentation/sysrq.txt
+++ b/Documentation/sysrq.txt
@@ -10,13 +10,32 @@ regardless of whatever else it is doing, unless it is completely locked up.
 *  How do I enable the magic SysRq key?
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 You need to say "yes" to 'Magic SysRq key (CONFIG_MAGIC_SYSRQ)' when
-configuring the kernel. When running on a kernel with SysRq compiled in, it
-may be DISABLED at run-time using following command:
-
-        echo "0" > /proc/sys/kernel/sysrq
-
-Note that previous versions disabled sysrq by default, and you were required
-to specifically enable it at run-time. That is not the case any longer.
+configuring the kernel. When running a kernel with SysRq compiled in,
+/proc/sys/kernel/sysrq controls the functions allowed to be invoked via
+the SysRq key. By default the file contains 1 which means that every
+possible SysRq request is allowed (in older versions SysRq was disabled
+by default, and you were required to specifically enable it at run-time
+but this is not the case any more). Here is the list of possible values
+in /proc/sys/kernel/sysrq:
+   0 - disable sysrq completely
+   1 - enable all functions of sysrq
+  >1 - bitmask of allowed sysrq functions (see below for detailed function
+       description):
+          2 - enable control of console logging level
+          4 - enable control of keyboard (SAK, unraw)
+          8 - enable debugging dumps of processes etc.
+         16 - enable sync command
+         32 - enable remount read-only
+         64 - enable signalling of processes (term, kill, oom-kill)
+        128 - allow reboot/poweroff
+        256 - allow nicing of all RT tasks
+
+You can set the value in the file by the following command:
+    echo "number" >/proc/sys/kernel/sysrq
+
+Note that the value of /proc/sys/kernel/sysrq influences only the invocation
+via a keyboard. Invocation of any operation via /proc/sysrq-trigger is always
+allowed.
 
 *  How do I use the magic SysRq key?
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -53,9 +72,7 @@ On all -  write a character to /proc/sysrq-trigger.  eg:
 'b'     - Will immediately reboot the system without syncing or unmounting
           your disks.
 
-'c'     - Intentionally crash the system without syncing or unmounting
-          your disks.  This is most useful if the NETDUMP client package
-          has been installed.
+'c'    - Will perform a kexec reboot in order to take a crashdump.
 
 'o'     - Will shut your system off (if configured and supported).
 
@@ -77,6 +94,8 @@ On all -  write a character to /proc/sysrq-trigger.  eg:
           it so that only emergency messages like PANICs or OOPSes would
           make it to your console.)
 
+'f'    - Will call oom_kill to kill a memory hog process
+
 'e'     - Send a SIGTERM to all processes, except for init.
 
 'i'     - Send a SIGKILL to all processes, except for init.
@@ -105,9 +124,8 @@ useful when you want to exit a program that will not let you switch consoles.
 re'B'oot is good when you're unable to shut down. But you should also 'S'ync
 and 'U'mount first.
 
-'C'rash immediately crashes your system.  This is most useful if the machine
-has been configured as a NETDUMP client because an OOPS report is generated
-and a kernel crash dump is sent to the NETDUMP server.
+'C'rashdump can be used to manually trigger a crashdump when the system is hung.
+The kernel needs to have been built with CONFIG_KEXEC enabled.
 
 'S'ync is great when your system is locked up, it allows you to sync your
 disks and will certainly lessen the chance of data loss and fscking. Note
@@ -153,7 +171,7 @@ the header 'include/linux/sysrq.h', this will define everything else you need.
 Next, you must create a sysrq_key_op struct, and populate it with A) the key
 handler function you will use, B) a help_msg string, that will print when SysRQ
 prints help, and C) an action_msg string, that will print right before your
-handler is called. Your handler must conform to the protoype in 'sysrq.h'.
+handler is called. Your handler must conform to the prototype in 'sysrq.h'.
 
 After the sysrq_key_op is created, you can call the macro 
 register_sysrq_key(int key, struct sysrq_key_op *op_p) that is defined in
@@ -184,17 +202,13 @@ you must call __handle_sysrq_nolock instead.
 
 *  I have more questions, who can I ask?
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-You may feel free to send email to myrdraal@deathsdoor.com, and I will
-respond as soon as possible.
- -Myrdraal
-
 And I'll answer any questions about the registration system you got, also
 responding as soon as possible.
  -Crutcher
 
 *  Credits
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Written by Mydraal <myrdraal@deathsdoor.com>
+Written by Mydraal <vulpyne@vulpyne.net>
 Updated by Adam Sulmicki <adam@cfar.umd.edu>
 Updated by Jeremy M. Dolan <jmd@turbogeek.org> 2001/01/28 10:15:59
 Added to by Crutcher Dunnavant <crutcher+kernel@datastacks.com>