[PATCH] tracing: Sample module to demonstrate kernel access to Ftrace Hi,
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.i...@oracle.com/ 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 Let me know if you have any questions. Thanks, Divya