Re: [PATCH] tracing: Sample module to demonstrate kernel access to Ftrace instances.
From: Divya Indi
Date: Tue Oct 15 2019 - 15:54:23 EST
[Apologies for multiple resends, formatting issue]
Hi Steven,
Thanks for taking a look.
This sample module is dependent on -
- commit: f45d122 tracing: Kernel access to Ftrace instances
- Patches pending review: https://lore.kernel.org/lkml/1565805327-579-1-git-send-email-divya.indi@xxxxxxxxxx/
I mentioned it in the cover page, but will add to this patch as well to avoid confusion.
So, I think the messages you are seeing is due to the absence of
Patches pending review: https://lore.kernel.org/lkml/1565805327-579-1-git-send-email-divya.indi@xxxxxxxxxx/
Let me know if you prefer to have the sample module and this patch-set (pending review) as part of one patch set.
For reference, adding the cover page details here -
------------------------------------------------------------------------------------------------------------------
This patch is for a sample module to demonstrate the use of APIs that
were introduced/exported in order to access Ftrace instances from within the kernel.
Please Note: This module is dependent on -
- commit: f45d122 tracing: Kernel access to Ftrace instances
- Patches pending review: https://lore.kernel.org/lkml/1565805327-579-1-git-send-email-divya.indi@xxxxxxxxxx/
The sample module creates/lookup a trace array called sample-instance on module load time.
We then start a kernel thread(simple-thread) to -
1) Enable tracing for event "sample_event" to buffer associated with the trace array - "sample-instance".
2) Start a timer that will disable tracing to this buffer after 5 sec. (Tracing disabled after 5 sec ie at count=4)
3) Write to the buffer using trace_array_printk()
4) Stop the kernel thread and destroy the buffer during module unload.
A sample output for the same -
# tracer: nop
#
# entries-in-buffer/entries-written: 16/16 #P:4
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / delay
# TASK-PID CPU# |||| TIMESTAMP FUNCTION
# | | | |||| | |
sample-instance-26797 [003] .... 955180.489833: simple_thread: trace_array_printk: count=0
sample-instance-26797 [003] .... 955180.489836: sample_event: count value=0 at jiffies=5249940864
sample-instance-26797 [003] .... 955181.513722: simple_thread: trace_array_printk: count=1
sample-instance-26797 [003] .... 955181.513724: sample_event: count value=1 at jiffies=5249941888
sample-instance-26797 [003] .... 955182.537629: simple_thread: trace_array_printk: count=2
sample-instance-26797 [003] .... 955182.537631: sample_event: count value=2 at jiffies=5249942912
sample-instance-26797 [003] .... 955183.561516: simple_thread: trace_array_printk: count=3
sample-instance-26797 [003] .... 955183.561518: sample_event: count value=3 at jiffies=5249943936
sample-instance-26797 [003] .... 955184.585423: simple_thread: trace_array_printk: count=4
sample-instance-26797 [003] .... 955184.585427: sample_event: count value=4 at jiffies=5249944960
sample-instance-26797 [003] .... 955185.609344: simple_thread: trace_array_printk: count=5
sample-instance-26797 [003] .... 955186.633241: simple_thread: trace_array_printk: count=6
sample-instance-26797 [003] .... 955187.657157: simple_thread: trace_array_printk: count=7
sample-instance-26797 [003] .... 955188.681039: simple_thread: trace_array_printk: count=8
sample-instance-26797 [003] .... 955189.704937: simple_thread: trace_array_printk: count=9
sample-instance-26797 [003] .... 955190.728840: simple_thread: trace_array_printk: count=10
--------------------------------------------------------------------------------------------------------------------
Thanks,
Divya
On 10/15/19 10:05 AM, Steven Rostedt wrote:
On Fri, 20 Sep 2019 16:59:26 -0700
Divya Indi <divya.indi@xxxxxxxxxx> wrote:
This is a sample module to demostrate the use of the newly introduced and
exported APIs to access Ftrace instances from within the kernel.
Newly introduced APIs used here -
1. Create a new trace array if it does not exist.
struct trace_array *trace_array_create(const char *name)
2. Destroy/Remove a trace array.
int trace_array_destroy(struct trace_array *tr)
3. Lookup a trace array, given its name.
struct trace_array *trace_array_lookup(const char *name)
4. Enable/Disable trace events:
int trace_array_set_clr_event(struct trace_array *tr, const char *system,
const char *event, int set);
Exported APIs -
1. trace_printk equivalent for instances.
int trace_array_printk(struct trace_array *tr,
unsigned long ip, const char *fmt, ...);
2. Helper function.
void trace_printk_init_buffers(void);
3. To decrement the reference counter.
void trace_array_put(struct trace_array *tr)
Signed-off-by: Divya Indi <divya.indi@xxxxxxxxxx>
Reviewed-by: Manjunath Patil <manjunath.b.patil@xxxxxxxxxx>
Reviewed-by: Joe Jin <joe.jin@xxxxxxxxxx>
---
samples/Kconfig | 7 ++
samples/Makefile | 1 +
samples/ftrace_instance/Makefile | 6 ++
samples/ftrace_instance/sample-trace-array.c | 134 +++++++++++++++++++++++++++
samples/ftrace_instance/sample-trace-array.h | 84 +++++++++++++++++
5 files changed, 232 insertions(+)
create mode 100644 samples/ftrace_instance/Makefile
create mode 100644 samples/ftrace_instance/sample-trace-array.c
create mode 100644 samples/ftrace_instance/sample-trace-array.h
I applied this patch but get this:
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c: In function âmytimer_handlerâ:
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c:35:2: error: implicit declaration of function âtrace_array_set_clr_eventâ; did you mean âtrace_set_clr_eventâ? [-Werror=implicit-function-declaration]
trace_array_set_clr_event(tr, "sample-subsystem", "sample_event", 0);
^~~~~~~~~~~~~~~~~~~~~~~~~
trace_set_clr_event
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c: In function âsimple_thread_funcâ:
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c:47:2: error: implicit declaration of function âtrace_array_printkâ; did you mean âtrace_seq_printfâ? [-Werror=implicit-function-declaration]
trace_array_printk(tr, _THIS_IP_, "trace_array_printk: count=%d\n",
^~~~~~~~~~~~~~~~~~
trace_seq_printf
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c: In function âsimple_threadâ:
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c:85:2: error: implicit declaration of function âtrace_array_putâ; did you mean âtrace_seq_putcâ? [-Werror=implicit-function-declaration]
trace_array_put(tr);
^~~~~~~~~~~~~~~
trace_seq_putc
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c: In function âsample_trace_array_initâ:
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c:100:7: error: implicit declaration of function âtrace_array_lookupâ; did you mean âradix_tree_lookupâ? [-Werror=implicit-function-declaration]
tr = trace_array_lookup("sample-instance");
^~~~~~~~~~~~~~~~~~
radix_tree_lookup
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c:100:5: warning: assignment to âstruct trace_array *â from âintâ makes pointer from integer without a cast [-Wint-conversion]
tr = trace_array_lookup("sample-instance");
^
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c:102:8: error: implicit declaration of function âtrace_array_createâ; did you mean âftrace_force_updateâ? [-Werror=implicit-function-declaration]
tr = trace_array_create("sample-instance");
^~~~~~~~~~~~~~~~~~
ftrace_force_update
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c:102:6: warning: assignment to âstruct trace_array *â from âintâ makes pointer from integer without a cast [-Wint-conversion]
tr = trace_array_create("sample-instance");
^
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c:110:2: error: implicit declaration of function âtrace_printk_init_buffersâ; did you mean âtrace_event_get_offsetsâ? [-Werror=implicit-function-declaration]
trace_printk_init_buffers();
^~~~~~~~~~~~~~~~~~~~~~~~~
trace_event_get_offsets
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c: In function âsample_trace_array_exitâ:
/work/git/linux-trace.git/samples/ftrace_instance/sample-trace-array.c:126:2: error: implicit declaration of function âtrace_array_destroyâ; did you mean âassoc_array_destroyâ? [-Werror=implicit-function-declaration]
trace_array_destroy(tr);
^~~~~~~~~~~~~~~~~~~
assoc_array_destroy
cc1: some warnings being treated as errors
make[3]: *** [/work/git/linux-trace.git/scripts/Makefile.build:266: samples/ftrace_instance/sample-trace-array.o] Error 1
make[2]: *** [/work/git/linux-trace.git/scripts/Makefile.build:509: samples/ftrace_instance] Error 2
make[1]: *** [/work/git/linux-trace.git/Makefile:1650: samples] Error 2
make[1]: *** Waiting for unfinished jobs....
-- Steve