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[PATCH] sysrq: showBlockedTasks is sysrq-W

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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: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Randy Dunlap 2007-01-31 23:48:17 -08:00 committed by Linus Torvalds
parent 7d8952440f
commit d346cce308
2 changed files with 46 additions and 40 deletions
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66
Documentation/sysrq.txt
View file

@ -1,6 +1,6 @@
Linux Magic System Request Key Hacks
Documentation for sysrq.c version 1.15
Last update: $Date: 2001/01/28 10:15:59 $
Documentation for sysrq.c
Last update: 2007-JAN-06
* 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
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?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@ -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
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
@ -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.
'd' - Shows all locks that are held.
'o' - Will shut your system off (if configured and supported).
's' - Will attempt to sync all mounted filesystems.
@ -87,38 +89,43 @@ On all - write a character to /proc/sysrq-trigger. eg:
'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.
'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
will be printed to your console. ('0', for example would make
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
'f' - Will call oom_kill to kill a memory hog process.
'e' - Send a SIGTERM to all processes, except for init.
'g' - Used by kgdb on ppc platforms.
'i' - Send a SIGKILL to all processes, except for init.
'l' - Send a SIGKILL to all processes, INCLUDING init. (Your system
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 :-)
* Okay, so what can I use them for?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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
trojan program is running at console and which could grab your password
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
sa'K' (Secure Access Key) is useful when you want to be sure there is no
trojan program running at console which could grab your password
when you would try to login. It will kill all programs on given console,
thus letting you make sure that the login prompt you see is actually
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: c2 compliant system, and it should not be mistaken as :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.
(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
"OK" and "Done" message appear on the screen.
The loglevel'0'-'9' is useful when your console is being flooded with
kernel messages you do not want to see. Setting '0' will prevent all but
The loglevels '0'-'9' are useful when your console is being flooded with
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
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
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.
* 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
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
sysrq.h, this will register the operation pointed to by 'op_p' at table
key 'key', if that slot in the table is blank. At module unload time, you must
call the macro unregister_sysrq_key(int key, struct sysrq_key_op *op_p), which
After the sysrq_key_op is created, you can call the kernel function
register_sysrq_key(int key, struct sysrq_key_op *op_p); this will
register the operation pointed to by 'op_p' at table key 'key',
if that slot in the table is blank. At module unload time, you must call
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
it is currently registered in that slot. This is in case the slot has been
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
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,
and 4 functions are exported for interface to it: __sysrq_lock_table,
__sysrq_unlock_table, __sysrq_get_key_op, and __sysrq_put_key_op. The
functions __sysrq_swap_key_ops and __sysrq_swap_key_ops_nolock are defined
in the header itself, and the REGISTER and UNREGISTER macros are built from
these. More complex (and dangerous!) manipulations of the table are possible
using these functions, but you must be careful to always lock the table before
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 :)
and 2 functions are exported for interface to it:
register_sysrq_key and unregister_sysrq_key.
Of course, never ever leave an invalid pointer in the table. I.e., when
your module that called register_sysrq_key() exits, it must call
unregister_sysrq_key() to clean up the sysrq key table entry that it used.
Null pointers in the table are always safe. :)
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

20
drivers/char/sysrq.c
View file

@ -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 = {
.handler = sysrq_handle_showstate_blocked,
.help_msg = "showBlockedTasks",
.help_msg = "shoW-blocked-tasks",
.action_msg = "Show Blocked State",
.enable_mask = SYSRQ_ENABLE_DUMP,
};
@ -315,15 +315,16 @@ static struct sysrq_key_op *sysrq_key_table[36] = {
&sysrq_loglevel_op, /* 9 */
/*
* Don't use for system provided sysrqs, it is handled specially on
* sparc and will never arrive
* a: Don't use for system provided sysrqs, it is handled specially on
* sparc and will never arrive.
*/
NULL, /* a */
&sysrq_reboot_op, /* b */
&sysrq_crashdump_op, /* c */
&sysrq_crashdump_op, /* c & ibm_emac driver debug */
&sysrq_showlocks_op, /* d */
&sysrq_term_op, /* e */
&sysrq_moom_op, /* f */
/* g: May be registered by ppc for kgdb */
NULL, /* g */
NULL, /* h */
&sysrq_kill_op, /* i */
@ -332,18 +333,19 @@ static struct sysrq_key_op *sysrq_key_table[36] = {
NULL, /* l */
&sysrq_showmem_op, /* m */
&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 */
&sysrq_showregs_op, /* p */
NULL, /* q */
&sysrq_unraw_op, /* r */
&sysrq_unraw_op, /* r */
&sysrq_sync_op, /* s */
&sysrq_showstate_op, /* t */
&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, /* w */
&sysrq_showstate_blocked_op, /* x */
&sysrq_showstate_blocked_op, /* w */
/* x: May be registered on ppc/powerpc for xmon */
NULL, /* x */
NULL, /* y */
NULL /* z */
};