This reverts commit 04db6e5f.

Odds are, we really don't want to revert all of these, and need to be
more careful in the future to make sure we don't break the build of
other arches.
Reported-by: NStephen Rothwell <sfr@canb.auug.org.au>
Cc: Jim Cromie <jim.cromie@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

These arent currently needed, so drop them.  Some will probably get
re-added when static-branches are added, but include loops prevent
that at present.
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

1- Call dynamic_debug_init() from early_initcall, not arch_initcall.
2- Call dynamic_debug_init_debugfs() from fs_initcall, not module_init.

RFC: This works for me on a 64 bit desktop and a i586 SBC, but is
untested on other arches.  I presume there is or was a reason
original code used arch_initcall, maybe the constraints have changed.

This makes facility available as soon as possible.

2nd change has a downside when dynamic_debug.verbose=1; all the
vpr_info()s called in the proc-fs code are activated, causing
voluminous output from dmesg.  TBD: Im unsure of this explanation, but
the output is there.  This could be fixed by changing those callsites
to v2pr_info(if verbose > 1).

1st change is still not early enough to enable pr_debugs in
kernel/params, so parsing of boot-args isnt logged.  The reparse of
those args is however visible after params.dyndbg="+p" is processed.
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Acked-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Pass module name into ddebug_exec_queries(), ddebug_exec_query(), and
ddebug_parse_query() as separate parameter.  In ddebug_parse_query(),
the module name is added into the query struct before the query-string
is parsed.  This allows the query-string to be shorter:

instead of:
   $modname.dyndbg="module $modname +fp"
do this:
   $modname.dyndbg="+fp"

Omitting "module $modname" from the query string is actually required
for $modname.dyndbg rules; the set-only-once check added in a previous
patch will throw an error if its added again.  ddebug_query="..." has
no $modname associated with it, so the query string may include it.

This also fixes redundant "module $modname" otherwise needed to handle
multiple queries per string:

   $modname.dyndbg="func foo +fp; func bar +fp"
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Acked-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Print ram usage of dynamic-debug tables and verbose section so user
knows cost of enabling CONFIG_DYNAMIC_DEBUG.  This only counts the
size of the _ddebug tables for builtins and the __verbose section that
they refer to, not those used in loadable modules.
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Acked-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

We dont want errors while parsing ddebug_query to unload ddebug
tables, so set success after tables are loaded, and return 0 after
query parsing is done.

Simplify error handling code since its no longer used for success,
and change goto label to out_err to clarify this.
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Acked-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Refactor ddebug_dyndbg_boot_param_cb and ddebug_dyndbg_module_param_cb
into a common helper function, and call it from both.  The handling of
foo.dyndbg is unneeded by the latter, but harmless.

The 2 callers differ only by pr_info and the return code they pass to
the helper for when an unknown param is handled.  I could slightly
reduce dmesg clutter by putting the vpr_info in the common helper,
after the return on_err, but that loses __func__ context, is overly
silent on module_cb unknown param errors, and the clutter is only when
dynamic_debug.verbose=1 anyway.
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Acked-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

With ddebug_dyndbg_boot_params_cb() handling bare dyndbg params, we
dont need ddebug_query param anymore.  Add a warning when processing
ddebug_query= param that it is deprecated, and to change it to dyndbg=

Add a deprecation notice for v3.8 to feature-removal-schedule.txt, and
add a suggested deprecation period of 3 releases to the header.
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Acked-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

This introduces a fake module param $module.dyndbg.  Its based upon
Thomas Renninger's $module.ddebug boot-time debugging patch from
https://lkml.org/lkml/2010/9/15/397

The 'fake' module parameter is provided for all modules, whether or
not they need it.  It is not explicitly added to each module, but is
implemented in callbacks invoked from parse_args.

For builtin modules, dynamic_debug_init() now directly calls
parse_args(..., &ddebug_dyndbg_boot_params_cb), to process the params
undeclared in the modules, just after the ddebug tables are processed.

While its slightly weird to reprocess the boot params, parse_args() is
already called repeatedly by do_initcall_levels().  More importantly,
the dyndbg queries (given in ddebug_query or dyndbg params) cannot be
activated until after the ddebug tables are ready, and reusing
parse_args is cleaner than doing an ad-hoc parse.  This reparse would
break options like inc_verbosity, but they probably should be params,
like verbosity=3.

ddebug_dyndbg_boot_params_cb() handles both bare dyndbg (aka:
ddebug_query) and module-prefixed dyndbg params, and ignores all other
parameters.  For example, the following will enable pr_debug()s in 4
builtin modules, in the order given:

  dyndbg="module params +p; module aio +p" module.dyndbg=+p pci.dyndbg

For loadable modules, parse_args() in load_module() calls
ddebug_dyndbg_module_params_cb().  This handles bare dyndbg params as
passed from modprobe, and errors on other unknown params.

Note that modprobe reads /proc/cmdline, so "modprobe foo" grabs all
foo.params, strips the "foo.", and passes these to the kernel.
ddebug_dyndbg_module_params_cb() is again called for the unknown
params; it handles dyndbg, and errors on others.  The "doing" arg
added previously contains the module name.

For non CONFIG_DYNAMIC_DEBUG builds, the stub function accepts
and ignores $module.dyndbg params, other unknowns get -ENOENT.

If no param value is given (as in pci.dyndbg example above), "+p" is
assumed, which enables all pr_debug callsites in the module.

The dyndbg fake parameter is not shown in /sys/module/*/parameters,
thus it does not use any resources.  Changes to it are made via the
control file.

Also change pr_info in ddebug_exec_queries to vpr_info,
no need to see it all the time.
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
CC: Thomas Renninger <trenn@suse.de>
CC: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Use vpr_info to declutter code, reduce indenting, and change one
additional pr_info call in ddebug_exec_queries.
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Acked-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Insert ddebug_exec_queries() in place of ddebug_exec_query().  It
splits the query string on [;\n], and calls ddebug_exec_query() on
each.  All queries are processed independent of errors, allowing a
query to fail, for example when a module is not installed.  Empty
lines and comments are skipped.  Errors are counted, and the last
error seen (negative) or the number of callsites found (0 or positive)
is returned.  Return code checks are altered accordingly.

With this, multiple queries can be given in ddebug_query, allowing
more selective enabling of callsites.  As a side effect, a set of
commands can be batched in:

	cat cmd-file > $DBGMT/dynamic_debug/control

We dont want a ddebug_query syntax error to kill the dynamic debug
facility, so dynamic_debug_init() zeros ddebug_exec_queries()'s return
code after logging the appropriate message, so that ddebug tables are
preserved and $DBGMT/dynamic_debug/control file is created.  This
would be appropriate even without accepting multiple queries.

This patch also alters ddebug_change() to return number of callsites
matched (which typically is the same as number of callsites changed).
ddebug_exec_query() also returns the number found, or a negative value
if theres a parse error on the query.

Splitting on [;\n] prevents their use in format-specs, but selecting
callsites on punctuation is brittle anyway, meaningful and selective
substrings are more typical.

Note: splitting queries on ';' before handling trailing #comments
means that a ';' also terminates a comment, and text after the ';' is
treated as another query.  This trailing query will almost certainly
result in a parse error and thus have no effect other than the error
message.  The double corner case with unexpected results is:

     ddebug_query="func foo +p # enable foo ; +p"
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Signed-off-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Factor pr_info(query) out of ddebug_parse_query, into vpr_info_dq(),
for reuse later.  Also change the printed labels: file, func to agree
with the query-spec keywords accepted in the control file.  Pass ""
when string is null, to avoid "(null)" output from sprintf.  For
format print, use precision to skip last char, assuming its '\n', no
great harm if not, its a debug msg.
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Signed-off-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

trim_prefix(path) skips past the absolute source path root, and
returns the pointer to the relative path from there.  It is used to
shorten the displayed path in $DBGMT/dynamic_debug/control via
ddebug_proc_show(), and in ddebug_change() to allow relative filenames
to be used in applied queries.  For example:

  ~# echo file kernel/freezer.c +p > $DBGMT/dynamic_debug/control

  kernel/freezer.c:128 [freezer]cancel_freezing p "  clean up: %s\012"

trim_prefix(path) insures common prefix before trimming it, so
out-of-tree module paths are shown as full absolute paths.
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Signed-off-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Current query write buffer is 256 bytes, on stack.  In comparison, the
ddebug_query boot-arg is 1024.  Allocate the buffer off heap, and
enlarge it to 4096 bytes, big enough for ~100 queries (at 40 bytes
each), and error out if not.  This makes it play nicely with large
query sets (to be added later).  The buffer should be enough for most
uses, and others should probably be split into subsets.

[jbaron@redhat.com: changed USER_BUF_PAGE from 4095 -> 4096 ]
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Signed-off-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

If a token begins with #, the remainder of query string is a comment,
so drop it.  Doing it here avoids '#' in quoted strings.
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Signed-off-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

If _ddebug table is empty (in a CONFIG_DYNAMIC_DEBUG build this
shouldn't happen), then warn (error?) and return early.  This skips
empty table scan and parsing of setup-string, including the pr_info
call noting the parse.  By inspection, copy return-code handling from
1st ddebug_add_module() callsite to 2nd.
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Signed-off-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Issue error when a match-spec is given multiple times in a rule.
Previous code kept last one, but was silent about it.  Docs imply only
one is allowed by saying match-specs are ANDed together, given that
module M cannot match both A and B.  Also error when last_line < 1st_line.
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Signed-off-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Change describe_flags() to emit '=[pmflt_]+' for current callsite
flags, or just '=_' when they're disabled.  Having '=' in output
allows a more selective grep expression; in contrast '-' may appear
in filenames, line-ranges, and format-strings.  '=' also has better
mnemonics, saying; "the current setting is equal to <flags>".

This allows grep "=_" <dbgfs>/dynamic_debug/control to see disabled
callsites while avoiding the many occurrences of " = " seen in format
strings.

Enlarge flagsbufs to handle additional flag char, and alter
ddebug_parse_flags() to allow flags=0, so that user can turn off all
debug flags via:

  ~# echo =_ > <dbgfs>/dynamic_debug/control
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Signed-off-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Convert 'if (x !=NULL)' checks into 'if (x)'.
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Signed-off-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Issue keyword/parsing errors even w/o verbose set;
uncover otherwize mysterious non-functionality.
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Signed-off-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Replace strcpy with strlcpy, and add define for the size constant.

[jbaron@redhat.com: Use DDEBUG_STRING_SIZE for overflow check]
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Signed-off-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Allow changing dynamic_debug verbosity at run-time, to ease debugging
of ddebug queries as you add them, improving usability.

at boot time: dynamic_debug.verbose=1
at runtime:
root@voyage:~# echo 1 > /sys/module/dynamic_debug/parameters/verbose
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Signed-off-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Currently any enabled dynamic-debug flag on a pr_debug callsite will
enable printing, even if _DPRINTK_FLAGS_PRINT is off.  Checking print
flag directly allows "-p" to disable callsites without fussing with
other flags, so the following disables everything, without altering
flags user may have set:

	echo -p > $DBGFS/dynamic_debug/control
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Signed-off-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Style cleanups.
Signed-off-by: NJim Cromie <jim.cromie@gmail.com>
Signed-off-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Dynamic debug recently added support for netdev_printk.  It uses
__netdev_printk() to support this functionality.  However, when CONFIG_NET
is not set, we get the following error:

lib/built-in.o: In function `__dynamic_netdev_dbg':
(.text+0x9fda): undefined reference to `__netdev_printk'

Fix this by making the call to netdev_printk() contingent upon CONFIG_NET.
 We could have fixed this by defining netdev_printk() to a 'no-op' in the
!CONFIG_NET case.  However, this is not consistent with how the networking
layer uses netdev_printk.  For example, CONFIG_NET is not set,
netdev_printk() does not have a 'no-op' definition defined.
Signed-off-by: NJason Baron <jbaron@redhat.com>
Acked-by: NRandy Dunlap <rdunlap@xenotime.net>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NAndrew Morton <akpm@google.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

We were using KERN_CONT to combine messages with their prefix.  However,
KERN_CONT is not smp safe, in the sense that it can interleave messages.
This interleaving can result in printks coming out at the wrong loglevel.
With the high frequency of printks that dynamic debug can produce this is
not desirable.

So make dynamic_emit_prefix() fill a char buf[64] instead of doing a
printk directly.  If we enable printing out of function, module, line, or
pid info, they are placed in this 64 byte buffer.  In my testing 64 bytes
was enough size to fulfill all requests.  Even if it's not, we can match
up the printk itself to see where it's from, so to me this is no big deal.

[akpm@linux-foundation.org: convert dangerous macro to C]
Signed-off-by: NJason Baron <jbaron@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: NAndrew Morton <akpm@google.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

The num_enabled accounting isn't actually used anywhere - remove them.
Signed-off-by: NJason Baron <jbaron@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: NAndrew Morton <akpm@google.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

This patch removes an unneeded include of linux/version.h from
lib/dynamic_debug.c - identified by 'make versioncheck'.
This is the only file in lib/ with this issue.
Signed-off-by: NJesper Juhl <jj@chaosbits.net>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Previously, if dynamic debug was enabled netdev_dbg() was using
dynamic_dev_dbg() to print out the underlying msg. Fix this by making
sure netdev_dbg() uses __netdev_printk().

Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Add pr_fmt(fmt) with __func__.
Converts "ddebug:" prefix to "dynamic_debug:".

Most likely the if (verbose) outputs could
also be converted from pr_info to pr_debug.
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Multiple printks with KERN_CONT can be interleaved by
other printks.  Reduce the likelihood of that interleaving
by consolidating multiple calls to printk.
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Adding dynamic_dev_dbg duplicated prefix output.
Consolidate that output to a single routine.
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Unlike dynamic_pr_debug, dynamic uses of dev_dbg can not
currently add task_pid/KBUILD_MODNAME/__func__/__LINE__
to selected debug output.

Add a new function similar to dynamic_pr_debug to
optionally emit these prefixes.

Cc: Aloisio Almeida <aloisio.almeida@openbossa.org>
Noticed-by: NAloisio Almeida <aloisio.almeida@openbossa.org>
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

This fixes a build breakage caused by
8ba6ebf5 "Dynamic debug: Add more flags"

Cc: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Add flags that allow the user to specify via debugfs whether or not the
module name, function name, line number and/or thread ID have to be
included in the printed message.
Signed-off-by: NBart Van Assche <bvanassche@acm.org>
Cc: Greg Banks <gnb@fmeh.org>
Cc: Konrad Rzeszutek Wilk <konrad@darnok.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

On older gcc (3.3) dynamic debug fails to compile:

include/net/inet_connection_sock.h: In function `inet_csk_reset_xmit_timer':
include/net/inet_connection_sock.h:236: error: duplicate label declaration `do_printk'
include/net/inet_connection_sock.h:219: error: this is a previous declaration
include/net/inet_connection_sock.h:236: error: duplicate label declaration `out'
include/net/inet_connection_sock.h:219: error: this is a previous declaration
include/net/inet_connection_sock.h:236: error: duplicate label `do_printk'
include/net/inet_connection_sock.h:236: error: duplicate label `out'

Fix, by reverting the usage of JUMP_LABEL() in dynamic debug for now.

Cc: <stable@kernel.org>
Reported-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Tested-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Having the ddebug_query= boot parameter it makes sense to set up
dynamic debug as soon as possible.

I expect sysfs files cannot be set up via an arch_initcall, because
this one is even before fs_initcall. Therefore I splitted the
dynamic_debug_init function into an early one and a later one providing
/sys/../dynamic_debug/control file.

Possibly dynamic_debug can be initialized even earlier, not sure whether
this still makes sense then. I picked up arch_initcall as it covers
quite a lot already.

Dynamic debug needs to allocate memory, therefore it's not easily possible to
set it up even before the command line gets parsed.
Therefore the boot param query string is stored in a temp string which is
applied when dynamic debug gets set up.

This has been tested with ddebug_query="file ec.c +p"
and I could retrieve pr_debug() messages early at boot during ACPI setup:
ACPI: EC: Look up EC in DSDT
ACPI: EC: ---> status = 0x08
ACPI: EC: transaction start
ACPI: EC: <--- command = 0x80
ACPI: EC: ~~~> interrupt
ACPI: EC: ---> status = 0x08
ACPI: EC: <--- data = 0xa4
...
ACPI: Interpreter enabled
ACPI: (supports S0 S3 S4 S5)
ACPI: Using IOAPIC for interrupt routing
ACPI: EC: ---> status = 0x00
ACPI: EC: transaction start
ACPI: EC: <--- command = 0x80
Signed-off-by: NThomas Renninger <trenn@suse.de>
Acked-by: jbaron@redhat.com
Acked-by: NPekka Enberg <penberg@cs.helsinki.fi>
CC: linux-acpi@vger.kernel.org
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Dynamic debug lacks the ability to enable debug messages at boot time.
One could patch initramfs or service startup scripts to write to
/sys/../dynamic_debug/control, but this sucks.

This patch makes it possible to pass a query in the same format one can
write to /sys/../dynamic_debug/control via boot param.
When dynamic debug gets initialized, this query will automatically be
applied.
Signed-off-by: NThomas Renninger <trenn@suse.de>
Acked-by: jbaron@redhat.com
Acked-by: NPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

The parsing and applying of dynamic debug strings is not only useful for
/sys/../dynamic_debug/control write access, but can also be used for
boot parameter parsing.
The boot parameter is introduced in a follow up patch.
Signed-off-by: NThomas Renninger <trenn@suse.de>
Acked-by: jbaron@redhat.com
Acked-by: NPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Now that there's still only a few users around, rename things to make
them more consistent.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20101014203625.448565169@chello.nl>
Signed-off-by: NIngo Molnar <mingo@elte.hu>