Commit Graph

38 Commits

Author SHA1 Message Date
Rusty Russell 784e2d7600 stop_machine: fix up ftrace.c
Simple conversion.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Abhishek Sagar <sagar.abhishek@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Steven Rostedt <rostedt@goodmis.org>
2008-07-28 12:16:31 +10:00
Ingo Molnar b2613e370d ftrace: build fix for ftraced_suspend
fix:

 kernel/trace/ftrace.c:1615: error: 'ftraced_suspend' undeclared (first use in this function)
 kernel/trace/ftrace.c:1615: error: (Each undeclared identifier is reported only once
 kernel/trace/ftrace.c:1615: error: for each function it appears in.)

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-11 16:46:50 +02:00
Steven Rostedt a2bb6a3d85 ftrace: add ftrace_kill_atomic
It has been suggested that I add a way to disable the function tracer
on an oops. This code adds a ftrace_kill_atomic. It is not meant to be
used in normal situations. It will disable the ftrace tracer, but will
not perform the nice shutdown that requires scheduling.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Cc: Steven Rostedt <srostedt@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-11 15:49:21 +02:00
Abhishek Sagar 98a05ed4bd ftrace: prevent ftrace modifications while being kprobe'd, v2
add two missing chunks for ftrace+kprobe.

Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-03 14:46:24 +02:00
Abhishek Sagar f22f9a89ce ftrace: avoid modifying kprobe'd records
Avoid modifying the mcount call-site if there is a kprobe installed on it.
These records are not marked as failed however. This allowed the filter
rules on them to remain up-to-date. Whenever the kprobe on the corresponding
record is removed, the record gets updated as normal.

Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-23 22:10:59 +02:00
Abhishek Sagar ecea656d1d ftrace: freeze kprobe'd records
Let records identified as being kprobe'd be marked as "frozen". The trouble
with records which have a kprobe installed on their mcount call-site is
that they don't get updated. So if such a function which is currently being
traced gets its tracing disabled due to a new filter rule (or because it
was added to the notrace list) then it won't be updated and continue being
traced. This patch allows scanning of all frozen records during tracing to
check if they should be traced.

Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-23 22:10:58 +02:00
Abhishek Sagar 395a59d0f8 ftrace: store mcount address in rec->ip
Record the address of the mcount call-site. Currently all archs except sparc64
record the address of the instruction following the mcount call-site. Some
general cleanups are entailed. Storing mcount addresses in rec->ip enables
looking them up in the kprobe hash table later on to check if they're kprobe'd.

Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Cc: davem@davemloft.net
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-23 22:10:56 +02:00
Ingo Molnar f22529351f namespacecheck: fixes
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-16 14:44:13 +02:00
Abhishek Sagar a4500b84c5 ftrace: fix "notrace" filtering priority
This is a fix to give notrace filter rules priority over "set_ftrace_filter"
rules.

This fix ensures that functions which are set to be filtered and are
concurrently marked as "notrace" don't get recorded. As of now, if
a record is marked as FTRACE_FL_FILTER and is enabled, then the notrace
flag is not checked. Tested on x86-32.

Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-14 08:32:29 +02:00
Abhishek Sagar 34078a5e44 ftrace: prevent freeing of all failed updates
Steven Rostedt wrote:
> If we unload a module and reload it, will it ever get converted again?

The intent was always to filter core kernel functions to prevent their freeing.
Here's a fix which should allow re-recording of module call-sites.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-10 11:59:05 +02:00
Abhishek Sagar eb9a7bf091 ftrace: add debugfs entry 'failures'
Identify functions which had their mcount call-site updates failed. This can
help us track functions which ftrace shouldn't fiddle with, and are thus not
being traced. If there is no race with any external agent which is modifying
the mcount call-site, then this file displays no entries (normal case).

Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-10 11:58:17 +02:00
Abhishek Sagar 1d74f2a0f6 ftrace: remove ftrace_ip_converted()
Remove the unneeded function ftrace_ip_converted().

Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-10 11:57:49 +02:00
Abhishek Sagar 0eb967012e ftrace: prevent freeing of all failed updates
Prevent freeing of records which cause problems and correspond to function from
core kernel text. A new flag, FTRACE_FL_CONVERTED is used to mark a record
as "converted". All other records are patched lazily to NOPs. Failed records
now also remain on frace_hash table. Each invocation of ftrace_record_ip now
checks whether the traced function has ever been recorded (including past
failures) and doesn't re-record it again.

Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-10 11:56:57 +02:00
Steven Rostedt ad90c0e3ce ftrace: user update and disable dynamic ftrace daemon
In dynamic ftrace, the mcount function starts off pointing to a stub
function that just returns.

On start up, the call to the stub is modified to point to a "record_ip"
function. The job of the record_ip function is to add the function to
a pre-allocated hash list. If the function is already there, it simply is
ignored, otherwise it is added to the list.

Later, a ftraced daemon wakes up and calls kstop_machine if any functions
have been recorded, and changes the calls to the recorded functions to
a simple nop.  If no functions were recorded, the daemon goes back to sleep.

The daemon wakes up once a second to see if it needs to update any newly
recorded functions into nops.  Usually it does not, but if a lot of code
has been executed for the first time in the kernel, the ftraced daemon
will call kstop_machine to update those into nops.

The problem currently is that there's no way to stop the daemon from doing
this, and it can cause unneeded latencies (800us which for some is bothersome).

This patch adds a new file /debugfs/tracing/ftraced_enabled. If the daemon
is active, reading this will return "enabled\n" and "disabled\n" when the
daemon is not running. To disable the daemon, the user can echo "0" or
"disable" into this file, and "1" or "enable" to re-enable the daemon.

Since the daemon is used to convert the functions into nops to increase
the performance of the system, I also added that anytime something is
written into the ftraced_enabled file, kstop_machine will run if there
are new functions that have been detected that need to be converted.

This way the user can disable the daemon but still be able to control the
conversion of the mcount calls to nops by simply,

  "echo 0 > /debugfs/tracing/ftraced_enabled"

when they need to do more conversions.

To see the number of converted functions:

  "cat /debugfs/tracing/dyn_ftrace_total_info"

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-02 12:50:04 +02:00
Abhishek Sagar 492a7ea5bc ftrace: fix updating of ftrace_update_cnt
Hi Ingo/Steven,

Ftrace currently maintains an update count which includes false updates,
i.e, updates which failed. If anything, such failures should be tracked
by some separate variable, but this patch provides a minimal fix.

Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Cc: rostedt@goodmis.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-26 22:52:10 +02:00
Abhishek Sagar ffdaa3582b ftrace: safe traversal of ftrace_hash hlist
Hi Steven,

I noticed that concurrent instances of ftrace_record_ip()
have a race between ftrace_hash list traversal during
ftrace_ip_in_hash() (before acquiring ftrace_shutdown_lock)
and ftrace_add_hash(). If it's so then this should fix it.

Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Cc: rostedt@goodmis.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-26 22:52:04 +02:00
Steven Rostedt 41c52c0db9 ftrace: set_ftrace_notrace feature
While debugging latencies in the RT kernel, I found that it would be nice
to be able to filter away functions from the trace than just to filter
on functions.

I added a new interface to the debugfs tracing directory called

  set_ftrace_notrace

When dynamic frace is enabled, this lets you filter away functions that will
not be recorded in the trace. It is similar to adding 'notrace' to those
functions but by doing it without recompiling the kernel.

Here's how set_ftrace_filter and set_ftrace_notrace interact. Remember, if
set_ftrace_filter is set, it removes all functions from the trace execpt for
those listed in the set_ftrace_filter. set_ftrace_notrace will prevent those
functions from being traced.

If you were to set one function in both set_ftrace_filter and
set_ftrace_notrace and that function was the same, then you would end up
with an empty trace.

the set of functions to trace is:

  set_ftrace_filter == empty then

     all functions not in set_ftrace_notrace

  else

     set of the set_ftrace_filter and not in set of set_ftrace_notrace.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-26 22:51:37 +02:00
Ingo Molnar 2d8b820b2e ftrace: cleanups
factor out code and clean it up.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 22:36:37 +02:00
Ingo Molnar 37135677e6 ftrace: fix mcount export bug
David S. Miller noticed the following bug: the -pg instrumentation
function callback is named differently on each platform. On x86 it
is mcount, on sparc it is _mcount. So the export does not make sense
in kernel/trace/ftrace.c - move it to x86.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 22:36:24 +02:00
David Miller aa5e5ceaf5 ftrace: remove packed attribute on ftrace_page.
It causes unaligned access traps on platforms like sparc
(ftrace_page may be marked packed, but once we return
a dyn_ftrace sub-object from this array to another piece
of code, the "packed" part of the typing information doesn't
propagate).

But also, it didn't serve any purpose either.  Even if packed,
on 64-bit or 32-bit, it didn't give us any more dyn_ftrace
entries per-page.

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 22:35:57 +02:00
Steven Rostedt 2bb6f8d638 ftrace: use raw_smp_processor_id for mcount functions
Due to debug hooks in the kernel that can change the way smp_processor_id
works, use raw_smp_processor_id in mcount called functions (namely
ftrace_record_ip). Currently we annotate most debug functions from calling
mcount, but we should not rely on that to prevent kernel lockups.

This patch uses the raw_smp_processor_id to prevent a recusive crash
that can happen if a debug hook in smp_processor_id calls mcount.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 22:01:34 +02:00
Steven Rostedt 07a267cdd2 ftrace: add UNINTERRUPTIBLE state for kftraced on disable
When dynamic ftrace fails and sets itself disabled, the ftraced daemon
will go back to sleep everytime it wakes up. The setting of the
ftraced state to UNINTERRUPTIBLE is skipped in this process, and the
daemon takes up 100% of the CPU.  This patch makes sure the ftraced daemon
sets itself to UNINTERRUPTIBLE in that loop.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 21:15:42 +02:00
Ingo Molnar e309b41dd6 ftrace: remove notrace
now that we have a kbuild method for notrace, no need to pollute the
C code with the annotations.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 20:58:28 +02:00
Steven Rostedt caf8cdebfb ftrace: remove address of function names
PowerPC is very fragile when it comes to use of function names
and function addresses.  ftrace needs to either use all function
addresses or function names (i.e. my_func as suppose to &my_func).

This patch chooses to use the names and not the addresses, and
makes ftrace consistent.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 20:56:31 +02:00
Ingo Molnar 9ff9cdb2d3 ftrace: cleanups
clean up recent code.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 20:56:05 +02:00
Steven Rostedt 4eebcc81a3 ftrace: disable tracing on failure
Since ftrace touches practically every function. If we detect any
anomaly, we want to fully disable ftrace. This patch adds code
to try shutdown ftrace as much as possible without doing any more
harm is something is detected not quite correct.

This only kills ftrace, this patch does have checks for other parts of
the tracer (irqsoff, wakeup, etc.).

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 20:54:16 +02:00
Steven Rostedt 37ad508419 ftrace - fix dynamic ftrace memory leak
The ftrace dynamic function update allocates a record to store the
instruction pointers that are being modified. If the modified
instruction pointer fails to update, then the record is marked as
failed and nothing more is done.

Worse, if the modification fails, but the record ip function is still
called, it will allocate a new record and try again. In just a matter
of time, will this cause a serious memory leak and crash the system.

This patch plugs this memory leak. When a record fails, it is
included back into the pool of records to be used. Now a record may
fail over and over again, but the number of allocated records will
not increase.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 20:54:04 +02:00
Ingo Molnar 750ed1a407 ftrace: timestamp syncing, prepare
rename and uninline now() to ftrace_now().

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 20:42:31 +02:00
Ingo Molnar 4bf39a9411 ftrace: cleanups
no code changed.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 20:42:20 +02:00
Steven Rostedt 77a2b37d22 ftrace: startup tester on dynamic tracing.
This patch adds a startup self test on dynamic code modification
and filters. The test filters on a specific function, makes sure that
no other function is traced, exectutes the function, then makes sure that
the function is traced.

This patch also fixes a slight bug with the ftrace selftest, where
tracer_enabled was not being set.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 20:41:06 +02:00
Ingo Molnar c7aafc5497 ftrace: cleanups
factor out code and clean it up.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 20:40:46 +02:00
Steven Rostedt e1c08bdd9f ftrace: force recording
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 20:40:29 +02:00
Steven Rostedt 5072c59fd4 ftrace: add filter select functions to trace
This patch adds two files to the debugfs system:

 /debugfs/tracing/available_filter_functions

and

 /debugfs/tracing/set_ftrace_filter

The available_filter_functions lists all functions that has been
recorded by the ftraced that has called the ftrace_record_ip function.
This is to allow users to see what functions have been converted
to nops and can be enabled for tracing.

To enable functions, simply echo the names (whitespace delimited)
into set_ftrace_filter. Simple wildcards are also allowed.

echo 'scheduler' > /debugfs/tracing/set_ftrace_filter

Will have only the scheduler be activated when tracing is enabled.

echo 'sched_*' > /debugfs/tracing/set_ftrace_filter

Will have only the functions starting with 'sched_' be activated.

echo '*lock' > /debugfs/tracing/set_ftrace_filter

Will have only functions ending with 'lock' be activated.

echo '*lock*' > /debugfs/tracing/set_ftrace_filter

Will have only functions with 'lock' in its name be activated.

Note: 'sched*lock' will not work. The only wildcards that are
allowed is an asterisk and the beginning and or end of the string
passed in.

Multiple names can be passed in with whitespace delimited:

echo 'scheduler *lock *acpi*' > /debugfs/tracing/set_ftrace_filter

is also the same as:

echo 'scheduler' > /debugfs/tracing/set_ftrace_filter
echo '*lock' >> /debugfs/tracing/set_ftrace_filter
echo '*acpi*' >> /debugfs/tracing/set_ftrace_filter

Appending does just that. It appends to the list.

To disable all filters simply echo an empty line in:

echo > /debugfs/tracing/set_ftrace_filter

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 20:38:41 +02:00
Steven Rostedt d61f82d066 ftrace: use dynamic patching for updating mcount calls
This patch replaces the indirect call to the mcount function
pointer with a direct call that will be patched by the
dynamic ftrace routines.

On boot up, the mcount function calls the ftace_stub function.
When the dynamic ftrace code is initialized, the ftrace_stub
is replaced with a call to the ftrace_record_ip, which records
the instruction pointers of the locations that call it.

Later, the ftraced daemon will call kstop_machine and patch all
the locations to nops.

When a ftrace is enabled, the original calls to mcount will now
be set top call ftrace_caller, which will do a direct call
to the registered ftrace function. This direct call is also patched
when the function that should be called is updated.

All patching is performed by a kstop_machine routine to prevent any
type of race conditions that is associated with modifying code
on the fly.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 20:33:47 +02:00
Steven Rostedt 3c1720f00b ftrace: move memory management out of arch code
This patch moves the memory management of the ftrace
records out of the arch code and into the generic code
making the arch code simpler.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 20:33:35 +02:00
Steven Rostedt b0fc494fae ftrace: add ftrace_enabled sysctl to disable mcount function
This patch adds back the sysctl ftrace_enabled. This time it is
defaulted to on, if DYNAMIC_FTRACE is configured. When ftrace_enabled
is disabled, the ftrace function is set to the stub return.

If DYNAMIC_FTRACE is also configured, on ftrace_enabled = 0,
the registered ftrace functions will all be set to jmps, but no more
new calls to ftrace recording (used to find the ftrace calling sites)
will be called.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 20:33:19 +02:00
Steven Rostedt 3d0833953e ftrace: dynamic enabling/disabling of function calls
This patch adds a feature to dynamically replace the ftrace code
with the jmps to allow a kernel with ftrace configured to run
as fast as it can without it configured.

The way this works, is on bootup (if ftrace is enabled), a ftrace
function is registered to record the instruction pointer of all
places that call the function.

Later, if there's still any code to patch, a kthread is awoken
(rate limited to at most once a second) that performs a stop_machine,
and replaces all the code that was called with a jmp over the call
to ftrace. It only replaces what was found the previous time. Typically
the system reaches equilibrium quickly after bootup and there's no code
patching needed at all.

e.g.

  call ftrace  /* 5 bytes */

is replaced with

  jmp 3f  /* jmp is 2 bytes and we jump 3 forward */
3:

When we want to enable ftrace for function tracing, the IP recording
is removed, and stop_machine is called again to replace all the locations
of that were recorded back to the call of ftrace.  When it is disabled,
we replace the code back to the jmp.

Allocation is done by the kthread. If the ftrace recording function is
called, and we don't have any record slots available, then we simply
skip that call. Once a second a new page (if needed) is allocated for
recording new ftrace function calls.  A large batch is allocated at
boot up to get most of the calls there.

Because we do this via stop_machine, we don't have to worry about another
CPU executing a ftrace call as we modify it. But we do need to worry
about NMI's so all functions that might be called via nmi must be
annotated with notrace_nmi. When this code is configured in, the NMI code
will not call notrace.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 20:33:09 +02:00
Arnaldo Carvalho de Melo 16444a8a40 ftrace: add basic support for gcc profiler instrumentation
If CONFIG_FTRACE is selected and /proc/sys/kernel/ftrace_enabled is
set to a non-zero value the ftrace routine will be called everytime
we enter a kernel function that is not marked with the "notrace"
attribute.

The ftrace routine will then call a registered function if a function
happens to be registered.

[ This code has been highly hacked by Steven Rostedt and Ingo Molnar,
  so don't blame Arnaldo for all of this ;-) ]

Update:
  It is now possible to register more than one ftrace function.
  If only one ftrace function is registered, that will be the
  function that ftrace calls directly. If more than one function
  is registered, then ftrace will call a function that will loop
  through the functions to call.

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-23 20:31:58 +02:00