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[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: 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
Linus Torvalds
parent
7d8952440f
commit
d346cce308
@ -1,6 +1,6 @@
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Linux Magic System Request Key Hacks
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Documentation for sysrq.c version 1.15
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Last update: $Date: 2001/01/28 10:15:59 $
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Documentation for sysrq.c
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Last update: 2007-JAN-06
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* What is the magic SysRq key?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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@ -35,7 +35,7 @@ You can set the value in the file by the following command:
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Note that the value of /proc/sys/kernel/sysrq influences only the invocation
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via a keyboard. Invocation of any operation via /proc/sysrq-trigger is always
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allowed.
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allowed (by a user with admin privileges).
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* How do I use the magic SysRq key?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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@ -58,7 +58,7 @@ On PowerPC - Press 'ALT - Print Screen (or F13) - <command key>,
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On other - If you know of the key combos for other architectures, please
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let me know so I can add them to this section.
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On all - write a character to /proc/sysrq-trigger. eg:
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On all - write a character to /proc/sysrq-trigger. e.g.:
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echo t > /proc/sysrq-trigger
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@ -74,6 +74,8 @@ On all - write a character to /proc/sysrq-trigger. eg:
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'c' - Will perform a kexec reboot in order to take a crashdump.
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'd' - Shows all locks that are held.
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'o' - Will shut your system off (if configured and supported).
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's' - Will attempt to sync all mounted filesystems.
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@ -87,38 +89,43 @@ On all - write a character to /proc/sysrq-trigger. eg:
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'm' - Will dump current memory info to your console.
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'n' - Used to make RT tasks nice-able
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'v' - Dumps Voyager SMP processor info to your console.
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'w' - Dumps tasks that are in uninterruptable (blocked) state.
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'x' - Used by xmon interface on ppc/powerpc platforms.
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'0'-'9' - Sets the console log level, controlling which kernel messages
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will be printed to your console. ('0', for example would make
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it so that only emergency messages like PANICs or OOPSes would
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make it to your console.)
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'f' - Will call oom_kill to kill a memory hog process
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'f' - Will call oom_kill to kill a memory hog process.
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'e' - Send a SIGTERM to all processes, except for init.
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'g' - Used by kgdb on ppc platforms.
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'i' - Send a SIGKILL to all processes, except for init.
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'l' - Send a SIGKILL to all processes, INCLUDING init. (Your system
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will be non-functional after this.)
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'h' - Will display help ( actually any other key than those listed
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'h' - Will display help (actually any other key than those listed
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above will display help. but 'h' is easy to remember :-)
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* Okay, so what can I use them for?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Well, un'R'aw is very handy when your X server or a svgalib program crashes.
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sa'K' (Secure Access Key) is useful when you want to be sure there are no
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trojan program is running at console and which could grab your password
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when you would try to login. It will kill all programs on given console
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and thus letting you make sure that the login prompt you see is actually
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sa'K' (Secure Access Key) is useful when you want to be sure there is no
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trojan program running at console which could grab your password
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when you would try to login. It will kill all programs on given console,
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thus letting you make sure that the login prompt you see is actually
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the one from init, not some trojan program.
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IMPORTANT: In its true form it is not a true SAK like the one in a :IMPORTANT
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IMPORTANT: c2 compliant system, and it should not be mistaken as :IMPORTANT
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IMPORTANT: such. :IMPORTANT
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It seems other find it useful as (System Attention Key) which is
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It seems others find it useful as (System Attention Key) which is
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useful when you want to exit a program that will not let you switch consoles.
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(For example, X or a svgalib program.)
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@ -139,8 +146,8 @@ OK or Done message...)
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Again, the unmount (remount read-only) hasn't taken place until you see the
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"OK" and "Done" message appear on the screen.
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The loglevel'0'-'9' is useful when your console is being flooded with
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kernel messages you do not want to see. Setting '0' will prevent all but
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The loglevels '0'-'9' are useful when your console is being flooded with
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kernel messages you do not want to see. Selecting '0' will prevent all but
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the most urgent kernel messages from reaching your console. (They will
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still be logged if syslogd/klogd are alive, though.)
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@ -152,7 +159,7 @@ processes.
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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That happens to me, also. I've found that tapping shift, alt, and control
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on both sides of the keyboard, and hitting an invalid sysrq sequence again
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will fix the problem. (ie, something like alt-sysrq-z). Switching to another
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will fix the problem. (i.e., something like alt-sysrq-z). Switching to another
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virtual console (ALT+Fn) and then back again should also help.
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* I hit SysRq, but nothing seems to happen, what's wrong?
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@ -174,11 +181,11 @@ handler function you will use, B) a help_msg string, that will print when SysRQ
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prints help, and C) an action_msg string, that will print right before your
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handler is called. Your handler must conform to the prototype in 'sysrq.h'.
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After the sysrq_key_op is created, you can call the macro
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register_sysrq_key(int key, struct sysrq_key_op *op_p) that is defined in
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sysrq.h, this will register the operation pointed to by 'op_p' at table
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key 'key', if that slot in the table is blank. At module unload time, you must
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call the macro unregister_sysrq_key(int key, struct sysrq_key_op *op_p), which
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After the sysrq_key_op is created, you can call the kernel function
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register_sysrq_key(int key, struct sysrq_key_op *op_p); this will
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register the operation pointed to by 'op_p' at table key 'key',
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if that slot in the table is blank. At module unload time, you must call
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the function unregister_sysrq_key(int key, struct sysrq_key_op *op_p), which
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will remove the key op pointed to by 'op_p' from the key 'key', if and only if
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it is currently registered in that slot. This is in case the slot has been
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overwritten since you registered it.
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@ -186,15 +193,12 @@ overwritten since you registered it.
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The Magic SysRQ system works by registering key operations against a key op
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lookup table, which is defined in 'drivers/char/sysrq.c'. This key table has
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a number of operations registered into it at compile time, but is mutable,
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and 4 functions are exported for interface to it: __sysrq_lock_table,
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__sysrq_unlock_table, __sysrq_get_key_op, and __sysrq_put_key_op. The
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functions __sysrq_swap_key_ops and __sysrq_swap_key_ops_nolock are defined
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in the header itself, and the REGISTER and UNREGISTER macros are built from
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these. More complex (and dangerous!) manipulations of the table are possible
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using these functions, but you must be careful to always lock the table before
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you read or write from it, and to unlock it again when you are done. (And of
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course, to never ever leave an invalid pointer in the table). Null pointers in
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the table are always safe :)
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and 2 functions are exported for interface to it:
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register_sysrq_key and unregister_sysrq_key.
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Of course, never ever leave an invalid pointer in the table. I.e., when
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your module that called register_sysrq_key() exits, it must call
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unregister_sysrq_key() to clean up the sysrq key table entry that it used.
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Null pointers in the table are always safe. :)
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If for some reason you feel the need to call the handle_sysrq function from
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within a function called by handle_sysrq, you must be aware that you are in
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@ -215,7 +215,7 @@ static void sysrq_handle_showstate_blocked(int key, struct tty_struct *tty)
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}
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static struct sysrq_key_op sysrq_showstate_blocked_op = {
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.handler = sysrq_handle_showstate_blocked,
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.help_msg = "showBlockedTasks",
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.help_msg = "shoW-blocked-tasks",
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.action_msg = "Show Blocked State",
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.enable_mask = SYSRQ_ENABLE_DUMP,
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};
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@ -315,15 +315,16 @@ static struct sysrq_key_op *sysrq_key_table[36] = {
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&sysrq_loglevel_op, /* 9 */
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/*
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* Don't use for system provided sysrqs, it is handled specially on
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* sparc and will never arrive
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* a: Don't use for system provided sysrqs, it is handled specially on
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* sparc and will never arrive.
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*/
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NULL, /* a */
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&sysrq_reboot_op, /* b */
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&sysrq_crashdump_op, /* c */
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&sysrq_crashdump_op, /* c & ibm_emac driver debug */
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&sysrq_showlocks_op, /* d */
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&sysrq_term_op, /* e */
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&sysrq_moom_op, /* f */
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/* g: May be registered by ppc for kgdb */
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NULL, /* g */
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NULL, /* h */
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&sysrq_kill_op, /* i */
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@ -332,18 +333,19 @@ static struct sysrq_key_op *sysrq_key_table[36] = {
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NULL, /* l */
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&sysrq_showmem_op, /* m */
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&sysrq_unrt_op, /* n */
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/* This will often be registered as 'Off' at init time */
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/* o: This will often be registered as 'Off' at init time */
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NULL, /* o */
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&sysrq_showregs_op, /* p */
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NULL, /* q */
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&sysrq_unraw_op, /* r */
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&sysrq_unraw_op, /* r */
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&sysrq_sync_op, /* s */
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&sysrq_showstate_op, /* t */
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&sysrq_mountro_op, /* u */
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/* May be assigned at init time by SMP VOYAGER */
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/* v: May be registered at init time by SMP VOYAGER */
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NULL, /* v */
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NULL, /* w */
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&sysrq_showstate_blocked_op, /* x */
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&sysrq_showstate_blocked_op, /* w */
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/* x: May be registered on ppc/powerpc for xmon */
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NULL, /* x */
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NULL, /* y */
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NULL /* z */
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};
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