Commit d346cce3 authored by Randy Dunlap's avatar Randy Dunlap Committed by Linus Torvalds
Browse files

[PATCH] sysrq: showBlockedTasks is sysrq-W 



Change SysRq showBlockedTasks from sysrq-X to sysrq-W and show that in the
Help message.

It was previously done via X, but X is already used for Xmon on ppc & powerpc
platforms and this collision needs to be avoided.

All callers of register_sysrq_key() are now marked in the sysrq op/key table.
I didn't mark 'h' as Help because Help is just printed for any unknown key,
such as '?'.

Added some omitted sysrq key entries in the sysrq.txt file.

Signed-off-by: default avatarRandy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7d895244

Documentation/sysrq.txt

+35 −31
Original line number Original line Diff line number Diff line 
Linux Magic System Request Key Hacks

Linux Magic System Request Key Hacks

Documentation for sysrq.c version 1.15

Documentation for sysrq.c

Last update: $Date: 2001/01/28 10:15:59 $

Last update: 2007-JAN-06





*  What is the magic SysRq key?

*  What is the magic SysRq key?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -35,7 +35,7 @@ You can set the value in the file by the following command: 




Note that the value of /proc/sys/kernel/sysrq influences only the invocation

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

via a keyboard. Invocation of any operation via /proc/sysrq-trigger is always

allowed.

allowed (by a user with admin privileges).





*  How do I use the magic SysRq key?

*  How do I use the magic SysRq key?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -58,7 +58,7 @@ On PowerPC - Press 'ALT - Print Screen (or F13) - <command key>, 
On other - If you know of the key combos for other architectures, please

On other - If you know of the key combos for other architectures, please

           let me know so I can add them to this section.

           let me know so I can add them to this section.





On all -  write a character to /proc/sysrq-trigger.  eg:

On all -  write a character to /proc/sysrq-trigger.  e.g.:





		echo t > /proc/sysrq-trigger

		echo t > /proc/sysrq-trigger
@@ -74,6 +74,8 @@ On all - write a character to /proc/sysrq-trigger. eg: 




'c'	- Will perform a kexec reboot in order to take a crashdump.

'c'	- Will perform a kexec reboot in order to take a crashdump.





'd'	- Shows all locks that are held.



'o'     - Will shut your system off (if configured and supported).

'o'     - Will shut your system off (if configured and supported).





's'     - Will attempt to sync all mounted filesystems.

's'     - Will attempt to sync all mounted filesystems.
@@ -87,21 +89,26 @@ On all - write a character to /proc/sysrq-trigger. eg: 




'm'     - Will dump current memory info to your console.

'm'     - Will dump current memory info to your console.





'n'	- Used to make RT tasks nice-able



'v'	- Dumps Voyager SMP processor info to your console.

'v'	- Dumps Voyager SMP processor info to your console.





'w'	- Dumps tasks that are in uninterruptable (blocked) state.



'x'	- Used by xmon interface on ppc/powerpc platforms.



'0'-'9' - Sets the console log level, controlling which kernel messages

'0'-'9' - Sets the console log level, controlling which kernel messages

          will be printed to your console. ('0', for example would make

          will be printed to your console. ('0', for example would make

          it so that only emergency messages like PANICs or OOPSes would

          it so that only emergency messages like PANICs or OOPSes would

          make it to your console.)

          make it to your console.)





'f'	- Will call oom_kill to kill a memory hog process

'f'	- Will call oom_kill to kill a memory hog process.





'e'     - Send a SIGTERM to all processes, except for init.

'e'     - Send a SIGTERM to all processes, except for init.





'i'     - Send a SIGKILL to all processes, except for init.

'g'	- Used by kgdb on ppc platforms.





'l'     - Send a SIGKILL to all processes, INCLUDING init. (Your system

'i'     - Send a SIGKILL to all processes, except for init.

          will be non-functional after this.)





'h'     - Will display help (actually any other key than those listed

'h'     - Will display help (actually any other key than those listed

          above will display help. but 'h' is easy to remember :-)

          above will display help. but 'h' is easy to remember :-)
@@ -110,15 +117,15 @@ On all - write a character to /proc/sysrq-trigger. eg: 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Well, un'R'aw is very handy when your X server or a svgalib program crashes.

Well, un'R'aw is very handy when your X server or a svgalib program crashes.





sa'K' (Secure Access Key) is useful when you want to be sure there are no

sa'K' (Secure Access Key) is useful when you want to be sure there is no

trojan program is running at console and which could grab your password

trojan program running at console which could grab your password

when you would try to login. It will kill all programs on given console

when you would try to login. It will kill all programs on given console,

and thus letting you make sure that the login prompt you see is actually

thus letting you make sure that the login prompt you see is actually

the one from init, not some trojan program.

the one from init, not some trojan program.

IMPORTANT: In its true form it is not a true SAK like the one in a :IMPORTANT

IMPORTANT: In its true form it is not a true SAK like the one in a :IMPORTANT

IMPORTANT: c2 compliant system, and it should not be mistaken as   :IMPORTANT

IMPORTANT: c2 compliant system, and it should not be mistaken as   :IMPORTANT

IMPORTANT: such.                                                   :IMPORTANT

IMPORTANT: such.                                                   :IMPORTANT

       It seems other find it useful as (System Attention Key) which is

       It seems others find it useful as (System Attention Key) which is

useful when you want to exit a program that will not let you switch consoles.

useful when you want to exit a program that will not let you switch consoles.

(For example, X or a svgalib program.)

(For example, X or a svgalib program.)
@@ -139,8 +146,8 @@ OK or Done message...) 
Again, the unmount (remount read-only) hasn't taken place until you see the

Again, the unmount (remount read-only) hasn't taken place until you see the

"OK" and "Done" message appear on the screen.

"OK" and "Done" message appear on the screen.





The loglevel'0'-'9' is useful when your console is being flooded with

The loglevels '0'-'9' are useful when your console is being flooded with

kernel messages you do not want to see. Setting '0' will prevent all but

kernel messages you do not want to see. Selecting '0' will prevent all but

the most urgent kernel messages from reaching your console. (They will

the most urgent kernel messages from reaching your console. (They will

still be logged if syslogd/klogd are alive, though.)

still be logged if syslogd/klogd are alive, though.)
@@ -152,7 +159,7 @@ processes. 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

That happens to me, also. I've found that tapping shift, alt, and control

That happens to me, also. I've found that tapping shift, alt, and control

on both sides of the keyboard, and hitting an invalid sysrq sequence again

on both sides of the keyboard, and hitting an invalid sysrq sequence again

will fix the problem. (ie, something like alt-sysrq-z). Switching to another

will fix the problem. (i.e., something like alt-sysrq-z). Switching to another

virtual console (ALT+Fn) and then back again should also help.

virtual console (ALT+Fn) and then back again should also help.





*  I hit SysRq, but nothing seems to happen, what's wrong?

*  I hit SysRq, but nothing seems to happen, what's wrong?
@@ -174,11 +181,11 @@ 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

prints help, and C) an action_msg string, that will print right before your

handler is called. Your handler must conform to the prototype 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 

After the sysrq_key_op is created, you can call the kernel function

register_sysrq_key(int key, struct sysrq_key_op *op_p) that is defined in

register_sysrq_key(int key, struct sysrq_key_op *op_p); this will

sysrq.h, this will register the operation pointed to by 'op_p' at table

register the operation pointed to by 'op_p' at table key 'key',

key 'key', if that slot in the table is blank. At module unload time, you must

if that slot in the table is blank. At module unload time, you must call

call the macro unregister_sysrq_key(int key, struct sysrq_key_op *op_p), which

the function unregister_sysrq_key(int key, struct sysrq_key_op *op_p), which

will remove the key op pointed to by 'op_p' from the key 'key', if and only if

will remove the key op pointed to by 'op_p' from the key 'key', if and only if

it is currently registered in that slot. This is in case the slot has been

it is currently registered in that slot. This is in case the slot has been

overwritten since you registered it.

overwritten since you registered it.
@@ -186,15 +193,12 @@ overwritten since you registered it. 
The Magic SysRQ system works by registering key operations against a key op

The Magic SysRQ system works by registering key operations against a key op

lookup table, which is defined in 'drivers/char/sysrq.c'. This key table has

lookup table, which is defined in 'drivers/char/sysrq.c'. This key table has

a number of operations registered into it at compile time, but is mutable,

a number of operations registered into it at compile time, but is mutable,

and 4 functions are exported for interface to it: __sysrq_lock_table,

and 2 functions are exported for interface to it:

__sysrq_unlock_table, __sysrq_get_key_op, and __sysrq_put_key_op. The

	register_sysrq_key and unregister_sysrq_key.

functions __sysrq_swap_key_ops and __sysrq_swap_key_ops_nolock are defined

Of course, never ever leave an invalid pointer in the table. I.e., when

in the header itself, and the REGISTER and UNREGISTER macros are built from

your module that called register_sysrq_key() exits, it must call

these. More complex (and dangerous!) manipulations of the table are possible

unregister_sysrq_key() to clean up the sysrq key table entry that it used.

using these functions, but you must be careful to always lock the table before

Null pointers in the table are always safe. :)

you read or write from it, and to unlock it again when you are done. (And of

course, to never ever leave an invalid pointer in the table). Null pointers in

the table are always safe :)





If for some reason you feel the need to call the handle_sysrq function from

If for some reason you feel the need to call the handle_sysrq function from

within a function called by handle_sysrq, you must be aware that you are in

within a function called by handle_sysrq, you must be aware that you are in

drivers/char/sysrq.c

+11 −9
Original line number Original line Diff line number Diff line
@@ -215,7 +215,7 @@ static void sysrq_handle_showstate_blocked(int key, struct tty_struct *tty) 
}

}

static struct sysrq_key_op sysrq_showstate_blocked_op = {

static struct sysrq_key_op sysrq_showstate_blocked_op = {

	.handler	= sysrq_handle_showstate_blocked,

	.handler	= sysrq_handle_showstate_blocked,

	.help_msg	= "showBlockedTasks",

	.help_msg	= "shoW-blocked-tasks",

	.action_msg	= "Show Blocked State",

	.action_msg	= "Show Blocked State",

	.enable_mask	= SYSRQ_ENABLE_DUMP,

	.enable_mask	= SYSRQ_ENABLE_DUMP,

};

};
@@ -315,15 +315,16 @@ static struct sysrq_key_op *sysrq_key_table[36] = { 
	&sysrq_loglevel_op,		/* 9 */

	&sysrq_loglevel_op,		/* 9 */





	/*

	/*

	 * Don't use for system provided sysrqs, it is handled specially on

	 * a: Don't use for system provided sysrqs, it is handled specially on

	 * sparc and will never arrive

	 * sparc and will never arrive.

	 */

	 */

	NULL,				/* a */

	NULL,				/* a */

	&sysrq_reboot_op,		/* b */

	&sysrq_reboot_op,		/* b */

	&sysrq_crashdump_op,		/* c */

	&sysrq_crashdump_op,		/* c & ibm_emac driver debug */

	&sysrq_showlocks_op,		/* d */

	&sysrq_showlocks_op,		/* d */

	&sysrq_term_op,			/* e */

	&sysrq_term_op,			/* e */

	&sysrq_moom_op,			/* f */

	&sysrq_moom_op,			/* f */

	/* g: May be registered by ppc for kgdb */

	NULL,				/* g */

	NULL,				/* g */

	NULL,				/* h */

	NULL,				/* h */

	&sysrq_kill_op,			/* i */

	&sysrq_kill_op,			/* i */
@@ -332,7 +333,7 @@ static struct sysrq_key_op *sysrq_key_table[36] = { 
	NULL,				/* l */

	NULL,				/* l */

	&sysrq_showmem_op,		/* m */

	&sysrq_showmem_op,		/* m */

	&sysrq_unrt_op,			/* n */

	&sysrq_unrt_op,			/* n */

	/* This will often be registered as 'Off' at init time */

	/* o: This will often be registered as 'Off' at init time */

	NULL,				/* o */

	NULL,				/* o */

	&sysrq_showregs_op,		/* p */

	&sysrq_showregs_op,		/* p */

	NULL,				/* q */

	NULL,				/* q */
@@ -340,10 +341,11 @@ static struct sysrq_key_op *sysrq_key_table[36] = { 
	&sysrq_sync_op,			/* s */

	&sysrq_sync_op,			/* s */

	&sysrq_showstate_op,		/* t */

	&sysrq_showstate_op,		/* t */

	&sysrq_mountro_op,		/* u */

	&sysrq_mountro_op,		/* u */

	/* May be assigned at init time by SMP VOYAGER */

	/* v: May be registered at init time by SMP VOYAGER */

	NULL,				/* v */

	NULL,				/* v */

	NULL,				/* w */

	&sysrq_showstate_blocked_op,	/* w */

	&sysrq_showstate_blocked_op,	/* x */

	/* x: May be registered on ppc/powerpc for xmon */

	NULL,				/* x */

	NULL,				/* y */

	NULL,				/* y */

	NULL				/* z */

	NULL				/* z */

};

};

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