There is currently no easy way to clear the trace buffer. Currently
the only way is to change the current tracer.
This patch lets the user clear the trace buffer by simply writing
into the trace files.
echo > /debug/tracing/trace
or to clear a single cpu (i.e. for CPU 1):
echo > /debug/tracing/per_cpu/cpu1/trace
Requested-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
The start/stop methods of a tracer should be able to be executed
in all contexts. This patch converts the power tracer to do so.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
The stopping and starting of a tracer should be light weight and
be able to be called in all contexts. The sched_switch grabbed
mutexes in the start/stop functions. This patch changes it to a
simple variable, on/off.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Impact: feature to allow better serialized clock
This patch adds an option called "global-clock" that will allow
the tracer to switch to a slower but more accurate (across CPUs)
clock.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
This patch adds a new function called ring_buffer_set_clock that
allows a tracer to assign its own clock source to the buffer.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Impact: fix memory leak
If event_format_read() exits early due to nonzero ppos, the
previous kmalloc doesn't get freed - might as well do the
check before the kmalloc and avoid the problem.
Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: =?ISO-8859-1?Q?Fr=E9d=E9ric?= Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1237270859.8033.141.camel@charm-linux>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: fix for losing comms in trace
The command lines of tasks are cached at sched switch to not need
to record them at every trace point. Disabling the tracing on stops
the recording of traces, but does not stop the caching of command lines.
When the tracing is off the cache may overflow and cause the tracing
to show incorrect tasks matching the PIDs.
This patch disables prevents updates to the comm cache when the ring buffer
is off.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Impact: fix to one cause of incorrect comm outputs in trace
The spinlock only protected the creation of a comm <=> pid pair.
But it was possible that a reader could look up a pid, and get the
wrong comm because it had no locking.
This also required changing trace_find_cmdline to copy the comm cache
and not just send back a pointer to it.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Impact: fix a dynamic tracing failure
Recently, the function and function graph tracers failed to use dynamic
tracing after the following commit:
fa9d13cf13
(ftrace: don't try to __ftrace_replace_code on !FTRACE_FL_CONVERTED rec)
The patch is right except a mistake on the check for the FTRACE_FL_CONVERTED
flag. The code patching is aborted in case of successfully nopped sites.
What we want is the opposite: ignore the callsites that haven't been nopped.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Impact: fix crashes when tracing cpumasks
While ring-buffer allocation, the cpumasks are allocated too,
including the tracing cpumask and the per-cpu file mask handler.
But these cpumasks are freed accidentally just after.
Fix it.
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1237164303-11476-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: fix possible locking imbalance
In case of ring buffer resize failure, tracing_set_tracer forgot to
release trace_types_lock. Fix it.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1237151439-6755-5-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Syscall tracing must select kallsysms.
The arch code builds a table to find the syscall metadata by syscall
number. It needs the syscalls names resolution from the symbol table
to know which name found on the syscalls metadatas match a function
pointer from the arch sys_call_table.
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1237151439-6755-4-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: fix syscall tracer enable/disable race
The current thread flag toggling is racy as shown in the following
scenario:
- task A is the last user of syscall tracing, it releases the
TIF_SYSCALL_FTRACE on each tasks
- at the same time task B start syscall tracing. refcount == 0 so
it sets up TIF_SYSCALL_FTRACE on each tasks.
The effect of the mixup is unpredictable.
So this fix adds a mutex on {start,stop}_syscall_tracing().
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Reported-by: Ingo Molnar <mingo@elte.hu>
LKML-Reference: <1237151439-6755-3-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: fix 'stuck' syscall tracer
The syscall tracer uses a refcounter to enable several users
simultaneously.
But the refcounter did not behave correctly and always restored
its value to 0 after calling start_syscall_tracing(). Therefore,
stop_syscall_tracing() couldn't release correctly the tasks from
tracing.
Also the tracer forgot to reset the buffer when it is released.
Drop the pointless refcount decrement on start_syscall_tracing()
and reset the buffer when we release the tracer.
This fixes two reported issue:
- when we switch from syscall tracer to another tracer, syscall
tracing continued.
- incorrect use of the refcount.
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1237151439-6755-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: new feature
This adds the generic support for syscalls tracing. This is
currently exploited through a devoted tracer but other tracing
engines can use it. (They just have to play with
{start,stop}_ftrace_syscalls() and use the display callbacks
unless they want to override them.)
The syscalls prototypes definitions are abused here to steal
some metadata informations:
- syscall name, param types, param names, number of params
The syscall addr is not directly saved during this definition
because we don't know if its prototype is available in the
namespace. But we don't really need it. The arch has just to
build a function able to resolve the syscall number to its
metadata struct.
The current tracer prints the syscall names, parameters names
and values (and their types optionally). Currently the value is
a raw hex but higher level values diplaying is on my TODO list.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1236955332-10133-2-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: save memory
The struct dyn_ftrace table is very large, this patch will save
about 50%.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Steven Rostedt <srostedt@redhat.com>
LKML-Reference: <49BA2C9F.8020009@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: cleanup
VFS layer has tested the file mode, we do not need test it.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Steven Rostedt <srostedt@redhat.com>
LKML-Reference: <49BA2BAB.6010608@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Do __ftrace_replace_code for !FTRACE_FL_CONVERTED rec will always
fail, we should ignore this rec.
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Cc: "Steven Rostedt ;" <rostedt@goodmis.org>
LKML-Reference: <49BA2472.4060206@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
If dyn_ftrace is freed before ftrace_release(), ftrace_release()
will free it again and make ftrace_free_records wrong.
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Cc: "Steven Rostedt ;" <rostedt@goodmis.org>
LKML-Reference: <49BA23D9.1050900@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Provide basic callbacks to do syscall tracing.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
LKML-Reference: <1236401580-5758-2-git-send-email-fweisbec@gmail.com>
[ simplified it to a trace_printk() for now. ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The binary_buffers directory in /debugfs/tracing held the files
to read the trace buffers in a binary format. This held one file
per CPU buffer. But we also have a per_cpu directory that holds
a way to read the pretty-print formats.
This patch moves the binary buffers into the per_cpu_directory:
# ls /debug/tracing/per_cpu/cpu1/
trace trace_pipe trace_pipe_raw
The new name is called "trace_pipe_raw". The binary buffers always
acted similar to trace_pipe, except that they produce raw data.
Requested-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Impact: documentation
The use of the double __builtin_contant_p checks in the event_trace_printk
can be confusing to developers and reviewers. This patch adds a comment
to explain why it is there.
Requested-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
LKML-Reference: <20090313122235.43EB.A69D9226@jp.fujitsu.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
In a private email conversation I explained how the ring buffer
page worked by using silly ASCII art. Ingo suggested that I add
that to the comments of the code.
Here it is.
Requested-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Unlike TRACE_FORMAT() macros, the TRACE_EVENT() macros do not show
the event name in the trace file. Knowing the event type in the trace
output is very useful.
Instead of:
task swapper:0 [140] ==> ntpd:3308 [120]
We now have:
sched_switch: task swapper:0 [140] ==> ntpd:3308 [120]
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
commit c3ffc7a40b
"Don't use tracing_record_cmdline() in workqueue tracer"
has a race window.
find_task_by_vpid() requires task_list_lock().
LKML-Reference: <20090313090042.43CD.A69D9226@jp.fujitsu.com>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
If the stack tracing is disabled (by default) the stack_trace file
will only contain the header:
# cat /debug/tracing/stack_trace
Depth Size Location (0 entries)
----- ---- --------
This can be frustrating to a developer that does not realize that the
stack tracer is disabled. This patch adds the following text:
# cat /debug/tracing/stack_trace
Depth Size Location (0 entries)
----- ---- --------
#
# Stack tracer disabled
#
# To enable the stack tracer, either add 'stacktrace' to the
# kernel command line
# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'
#
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
The binary printk saves a pointer to the format string in the ring buffer.
On output, the format is processed. But if the user is reading the
ring buffer through a binary interface, the pointer is meaningless.
This patch creates a file called printk_formats that maps the pointers
to the formats.
# cat /debug/tracing/printk_formats
0xffffffff80713d40 : "irq_handler_entry: irq=%d handler=%s\n"
0xffffffff80713d48 : "lock_acquire: %s%s%s\n"
0xffffffff80713d50 : "lock_release: %s\n"
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Impact: speed up on event tracing
The event_trace_printk is currently a wrapper function that calls
trace_vprintk. Because it uses a variable for the fmt it misses out
on the optimization of using the binary printk.
This patch makes event_trace_printk into a macro wrapper to use the
fmt as the same as the trace_printks.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Impact: fix callsites with dynamic format strings
Since its new binary implementation, trace_printk() internally uses static
containers for the format strings on each callsites. But the value is
assigned once at build time, which means that it can't take dynamic
formats.
So this patch unearthes the raw trace_printk implementation for the callers
that will need trace_printk to be able to carry these dynamic format
strings. The trace_printk() macro will use the appropriate implementation
for each callsite. Most of the time however, the binary implementation will
still be used.
The other impact of this patch is that mmiotrace_printk() will use the old
implementation because it calls the low level trace_vprintk and we can't
guess here whether the format passed in it is dynamic or not.
Some parts of this patch have been written by Steven Rostedt (most notably
the part that chooses the appropriate implementation for each callsites).
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Impact: do not confuse user on small trace buffer sizes
When the system boots up, the trace buffer is small to conserve memory.
It is only two pages per online CPU. When the tracer is used, it expands
to the default value.
This can confuse the user if they look at the buffer size and see only
7, but then later they see 1408.
# cat /debug/tracing/buffer_size_kb
7
# echo sched_switch > /debug/tracing/current_tracer
# cat /debug/tracing/buffer_size_kb
1408
This patch tries to help remove this confustion by showing that the
buffer has not been expanded.
# cat /debug/tracing/buffer_size_kb
7 (expanded: 1408)
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Impact: speed up and remove possible races
The get_online_cpus was added to the ring buffer because the original
design would free the ring buffer on a CPU that was being taken
off line. The final design kept the ring buffer around even when the
CPU was taken off line. This is to allow a user to still read the
information on that ring buffer.
Most of the get_online_cpus are no longer needed since the ring buffer will
not disappear from the use cases.
Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
The hotplug code in the ring buffers is for use with CPU hotplug,
not generic hotplug.
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Impact: prevent races with ring_buffer_expanded
This patch places the expanding of the tracing buffer under the
protection of the trace_types_lock mutex. It is highly unlikely
that there would be any contention, but better safe than sorry.
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Impact: cleanup
Some of the comments about the trace buffer resizing is gobbledygook.
And I wonder why people question if I'm a native English speaker.
This patch makes the comments make a bit more sense.
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Impact: save on memory
Currently, a ring buffer was allocated for each "possible_cpus". On
some systems, this is the same as NR_CPUS. Thus, if a system defined
NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless
ring buffers taking up space. With a default buffer of 3 megs, this
could be quite drastic.
This patch changes the ring buffer code to only allocate ring buffers
for online CPUs. If a CPU goes off line, we do not free the buffer.
This is because the user may still have trace data in that buffer
that they would like to look at.
Perhaps in the future we could add code to delete a ring buffer if
the CPU is offline and the ring buffer becomes empty.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Impact: fix to task live locking on reading trace_pipe on one CPU
The same code is used for both trace_pipe (all CPUS) and the per_cpu
trace_pipe file. When there is no data to read, it will check for
signals and wait on the trace wait queue.
The problem happens with the per_cpu wait. The trace_wait code checks
all CPUs. Thus, if there's data in another CPU buffer, then it will
exit the wait, without checking for signals or waiting on the wait queue.
It would then try to read the empty buffer, and since that will just
return nothing, then it will try to wait again. Unfortunately, that will
again fail due to there still being data in the other buffers. This
ends up with a live lock for the task.
This patch fixes the trace_wait to be aware that the iterator may only
be waiting on a single buffer.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
To save memory, the tracer ring buffers are set to a minimum.
The activating of a trace expands the ring buffer size. This patch
adds this expanding, when an event is activated.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Impact: less memory impact on systems not using tracer
When the kernel boots up that has tracing configured, it allocates
the default size of the ring buffer. This currently happens to be
1.4Megs per possible CPU. This is quite a bit of wasted memory if
the system is never using the tracer.
The current solution is to keep the ring buffers to a minimum size
until the user uses them. Once a tracer is piped into the current_tracer
the ring buffer will be expanded to the default size. If the user
changes the size of the ring buffer, it will take the size given
by the user immediately.
If the user adds a "ftrace=" to the kernel command line, then the ring
buffers will be set to the default size on initialization.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
