Commit Graph

66 Commits

Author SHA1 Message Date
Ingo Molnar
6d5b43a67a Merge branch 'tip/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace into tracing/urgent 2008-11-19 09:00:50 +01:00
Steven Rostedt
32464779a1 ftrace: fix dyn ftrace filter selection
Impact: clean up and fix for dyn ftrace filter selection

The previous logic of the dynamic ftrace selection of enabling
or disabling functions was complex and incorrect. This patch simplifies
the code and corrects the usage. This simplification also makes the
code more robust.

Here is the correct logic:

  Given a function that can be traced by dynamic ftrace:

  If the function is not to be traced, disable it if it was enabled.
  (this is if the function is in the set_ftrace_notrace file)

  (filter is on if there exists any functions in set_ftrace_filter file)

  If the filter is on, and we are enabling functions:
    If the function is in set_ftrace_filter, enable it if it is not
      already enabled.
    If the function is not in set_ftrace_filter, disable it if it is not
      already disabled.

  Otherwise, if the filter is off and we are enabling function tracing:
    Enable the function if it is not already enabled.

  Otherwise, if we are disabling function tracing:
    Disable the function if it is not already disabled.

This code now sets or clears the ENABLED flag in the record, and at the
end it will enable the function if the flag is set, or disable the function
if the flag is cleared.

The parameters for the function that does the above logic is also
simplified. Instead of passing in confusing "new" and "old" where
they might be swapped if the "enabled" flag is not set. The old logic
even had one of the above always NULL and had to be filled in. The new
logic simply passes in one parameter called "nop". A "call" is calculated
in the code, and at the end of the logic, when we know we need to either
disable or enable the function, we can then use the "nop" and "call"
properly.

This code is more robust than the previous version.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-19 00:19:47 -05:00
Steven Rostedt
8204327831 ftrace: make filtered functions effective on setting
Impact: fix filter selection to apply when set

It can be confusing when the set_filter_functions is set (or cleared)
and the functions being recorded by the dynamic tracer does not
match.

This patch causes the code to be updated if the function tracer is
enabled and the filter is changed.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-19 00:18:54 -05:00
Steven Rostedt
f10ed36ec1 ftrace: fix set_ftrace_filter
Impact: fix of output of set_ftrace_filter

The commit "ftrace: do not show freed records in
             available_filter_functions"

Removed a bit too much from the set_ftrace_filter code, where we now see
all functions in the set_ftrace_filter file even when we set a filter.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-19 00:17:45 -05:00
walimis
5821e1b74f function tracing: fix wrong pos computing when read buffer has been fulfilled
Impact: make output of available_filter_functions complete

phenomenon:

The first value of dyn_ftrace_total_info is not equal with
`cat available_filter_functions | wc -l`, but they should be equal.

root cause:

When printing functions with seq_printf in t_show, if the read buffer
is just overflowed by current function record, then this function
won't be printed to user space through read buffer, it will
just be dropped. So we can't see this function printing.

So, every time the last function to fill the read buffer, if overflowed,
will be dropped.

This also applies to set_ftrace_filter if set_ftrace_filter has
more bytes than read buffer.

fix:

Through checking return value of seq_printf, if less than 0, we know
this function doesn't be printed. Then we decrease position to force
this function to be printed next time, in next read buffer.

Another little fix is to show correct allocating pages count.

Signed-off-by: walimis <walimisdev@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-16 08:32:05 +01:00
Steven Rostedt
a358324466 ring-buffer: buffer record on/off switch
Impact: enable/disable ring buffer recording API added

Several kernel developers have requested that there be a way to stop
recording into the ring buffers with a simple switch that can also
be enabled from userspace. This patch addes a new kernel API to the
ring buffers called:

 tracing_on()
 tracing_off()

When tracing_off() is called, all ring buffers will not be able to record
into their buffers.

tracing_on() will enable the ring buffers again.

These two act like an on/off switch. That is, there is no counting of the
number of times tracing_off or tracing_on has been called.

A new file is added to the debugfs/tracing directory called

  tracing_on

This allows for userspace applications to also flip the switch.

  echo 0 > debugfs/tracing/tracing_on

disables the tracing.

  echo 1 > /debugfs/tracing/tracing_on

enables it.

Note, this does not disable or enable any tracers. It only sets or clears
a flag that needs to be set in order for the ring buffers to write to
their buffers. It is a global flag, and affects all ring buffers.

The buffers start out with tracing_on enabled.

There are now three flags that control recording into the buffers:

 tracing_on: which affects all ring buffer tracers.

 buffer->record_disabled: which affects an allocated buffer, which may be set
     if an anomaly is detected, and tracing is disabled.

 cpu_buffer->record_disabled: which is set by tracing_stop() or if an
     anomaly is detected. tracing_start can not reenable this if
     an anomaly occurred.

The userspace debugfs/tracing/tracing_enabled is implemented with
tracing_stop() but the user space code can not enable it if the kernel
called tracing_stop().

Userspace can enable the tracing_on even if the kernel disabled it.
It is just a switch used to stop tracing if a condition was hit.
tracing_on is not for protecting critical areas in the kernel nor is
it for stopping tracing if an anomaly occurred. This is because userspace
can reenable it at any time.

Side effect: With this patch, I discovered a dead variable in ftrace.c
  called tracing_on. This patch removes it.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2008-11-11 15:02:04 -05:00
Frederic Weisbecker
0b6e4d56bf ftrace: perform an initialization for ftrace to enable it
Impact: corrects a bug which made the non-dyn function tracer not functional

With latest git, the non-dynamic function tracer didn't get any trace.

The problem was the fact that ftrace_enabled wasn't initialized to 1
because ftrace hasn't any init function when DYNAMIC_FTRACE is disabled.

So when a tracer tries to register an ftrace_ops struct,
__register_ftrace_function failed to set the hook.

This patch corrects it by setting an init function to initialize
ftrace during the boot.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-28 19:15:58 +01:00
Ingo Molnar
f17845e5d9 ftrace: warning in kernel/trace/ftrace.c
this warning:

  kernel/trace/ftrace.c:189: warning: ‘frozen_record_count’ defined but not used

triggers because frozen_record_count is only used in the KCONFIG_MARKERS
case. Move the variable it there.

Alas, this frozen-record facility seems to have little use. The
frozen_record_count variable is not used by anything, nor the flags.

So this section might need a bit of dead-code-removal care as well.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-24 12:52:44 +02:00
Ingo Molnar
66b0de3569 ftrace: fix build failure
fix:

 kernel/trace/ftrace.c: In function 'ftrace_release':
 kernel/trace/ftrace.c:271: error: implicit declaration of function 'ftrace_release_hash'

release_hash is not needed without dftraced.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-23 16:11:03 +02:00
Steven Rostedt
08f5ac906d ftrace: remove ftrace hash
The ftrace hash was used by the ftrace_daemon code. The record ip function
would place the calling address (ip) into the hash. The daemon would later
read the hash and modify that code.

The hash complicates the code. This patch removes it.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-23 16:00:24 +02:00
Steven Rostedt
4d296c2432 ftrace: remove mcount set
The arch dependent function ftrace_mcount_set was only used by the daemon
start up code. This patch removes it.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-23 16:00:23 +02:00
Steven Rostedt
cb7be3b2fc ftrace: remove daemon
The ftrace daemon is complex and error prone.  This patch strips it out
of the code.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-23 16:00:22 +02:00
Steven Rostedt
6912896e99 ftrace: add ftrace warn on to disable ftrace
Add ftrace warn on to disable ftrace as well as report a warning.

[ Thanks to Andrew Morton for suggesting using the WARN_ON return value ]

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-23 16:00:20 +02:00
Steven Rostedt
81adbdc029 ftrace: only have ftrace_kill atomic
When an anomaly is detected, we need a way to completely disable
ftrace. Right now we have two functions: ftrace_kill and ftrace_kill_atomic.
The ftrace_kill tries to do it in a "nice" way by converting everything
back to a nop.

The "nice" way is dangerous itself, so this patch removes it and only
has the "atomic" version, which is all that is needed.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-23 16:00:19 +02:00
Steven Rostedt
593eb8a2d6 ftrace: return error on failed modified text.
Have the ftrace_modify_code return error values:

  -EFAULT on error of reading the address

  -EINVAL if what is read does not match what it expected

  -EPERM  if the write fails to update after a successful match.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-23 16:00:13 +02:00
Steven Rostedt
bd95b88d9e ftrace: release functions from hash
The x86 architecture uses a static recording of mcount caller locations
and is not affected by this patch.

For architectures still using the dynamic ftrace daemon, this patch is
critical. It removes the race between the recording of a function that
calls mcount, the unloading of a module, and the ftrace daemon updating
the call sites.

This patch adds the releasing of the hash functions that the daemon uses
to update the mcount call sites. When a module is unloaded, not only
are the replaced call site table update, but now so is the hash recorded
functions that the ftrace daemon will use.

Again, architectures that implement MCOUNT_RECORD are not affected by
this (which currently only x86 has).

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-20 18:27:01 +02:00
Steven Rostedt
05736a427f ftrace: warn on failure to disable mcount callers
With the recent updates to ftrace, there should not be any failures when
modifying the code. If there is, then we need to warn about it.

This patch has a cleaned up version of the code that I used to discover
that the weak symbols were causing failures.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-14 10:38:11 +02:00
Steven Noonan
71c67d58b5 ftrace: mcount_addr defined but not used
When CONFIG_DYNAMIC_FTRACE isn't used, neither is mcount_addr. This
patch eliminates that warning.

Signed-off-by: Steven Noonan <steven@uplinklabs.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-14 10:37:58 +02:00
Steven Rostedt
644f991d4b ftrace: fix unlocking of hash
This must be brown paper bag week for Steven Rostedt!

While working on ftrace for PPC, I discovered that the hash locking done
when CONFIG_FTRACE_MCOUNT_RECORD is not set, is totally incorrect.

With a cut and paste error, I had the hash lock macro to lock for both
hash_lock _and_ hash_unlock!

This bug did not affect x86 since this bug was introduced when
CONFIG_FTRACE_MCOUNT_RECORD was added to x86.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-14 10:36:58 +02:00
Steven Rostedt
3b47bfc1fc ftrace: remove direct reference to mcount in trace code
The mcount record method of ftrace scans objdump for references to mcount.
Using mcount as the reference to test if the calls to mcount being replaced
are indeed calls to mcount, this use of mcount was also caught as a
location to change. Using a variable that points to the mcount address
moves this reference into the data section that is not scanned, and
we do not use a false location to try and modify.

The warn on code was what was used to detect this bug.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-14 10:36:22 +02:00
Ingo Molnar
ac8825ec6d ftrace: clean up macro usage
enclose the argument in parenthesis. (especially since we cast it,
which is a high prio operation)

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-14 10:36:09 +02:00
Stephen Rothwell
2d7da80f71 ftrace: fix build failure
After disabling FTRACE_MCOUNT_RECORD via a patch, a dormant build
failure surfaced:

 kernel/trace/ftrace.c: In function 'ftrace_record_ip':
 kernel/trace/ftrace.c:416: error: incompatible type for argument 1 of '_spin_lock_irqsave'
 kernel/trace/ftrace.c:433: error: incompatible type for argument 1 of '_spin_lock_irqsave'

Introduced by commit 6dad8e07f4c10b17b038e84d29f3ca41c2e55cd0 ("ftrace:
add necessary locking for ftrace records").

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-14 10:36:06 +02:00
Steven Rostedt
99ecdc43bc ftrace: add necessary locking for ftrace records
The new design of pre-recorded mcounts and updating the code outside of
kstop_machine has changed the way the records themselves are protected.

This patch uses the ftrace_lock to protect the records. Note, the lock
still does not need to be taken within calls that are only called via
kstop_machine, since the that code can not run while the spin lock is held.

Also removed the hash_lock needed for the daemon when MCOUNT_RECORD is
configured. Also did a slight cleanup of an unused variable.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-14 10:35:47 +02:00
Steven Rostedt
00fd61aee1 ftrace: do not init module on ftrace disabled
If one of the self tests of ftrace has disabled the function tracer,
do not run the code to convert the mcount calls in modules.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-14 10:35:43 +02:00
Steven Rostedt
fed1939c64 ftrace: remove old pointers to mcount
When a mcount pointer is recorded into a table, it is used to add or
remove calls to mcount (replacing them with nops). If the code is removed
via removing a module, the pointers still exist.  At modifying the code
a check is always made to make sure the code being replaced is the code
expected. In-other-words, the code being replaced is compared to what
it is expected to be before being replaced.

There is a very small chance that the code being replaced just happens
to look like code that calls mcount (very small since the call to mcount
is relative). To remove this chance, this patch adds ftrace_release to
allow module unloading to remove the pointers to mcount within the module.

Another change for init calls is made to not trace calls marked with
__init. The tracing can not be started until after init is done anyway.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-14 10:35:12 +02:00
Steven Rostedt
a9fdda33cd ftrace: do not show freed records in available_filter_functions
Seems that freed records can appear in the available_filter_functions list.
This patch fixes that.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-14 10:35:05 +02:00
Steven Rostedt
90d595fe5c ftrace: enable mcount recording for modules
This patch enables the loading of the __mcount_section of modules and
changing all the callers of mcount into nops.

The modification is done before the init_module function is called, so
again, we do not need to use kstop_machine to make these changes.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-14 10:34:47 +02:00
Steven Rostedt
68bf21aa15 ftrace: mcount call site on boot nops core
This is the infrastructure to the converting the mcount call sites
recorded by the __mcount_loc section into nops on boot. It also allows
for using these sites to enable tracing as normal. When the __mcount_loc
section is used, the "ftraced" kernel thread is disabled.

This uses the current infrastructure to record the mcount call sites
as well as convert them to nops. The mcount function is kept as a stub
on boot up and not converted to the ftrace_record_ip function. We use the
ftrace_record_ip to only record from the table.

This patch does not handle modules. That comes with a later patch.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-14 10:34:44 +02:00
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