Man page 9 : trace_puts

trace_puts - write a string into the ftrace buffer

trace_puts( str );

str
    the string to record

__trace_bputs is an internal function for trace_puts and the ip is passed in via the trace_puts macro.

This is similar to trace_printk but is made for those really fast paths that a developer wants the least amount of « Heisenbug » affects, where the processing of the print format is still too much.

This function allows a kernel developer to debug fast path sections that printk is not appropriate for. By scattering in various printk like tracing in the code, a developer can quickly see where problems are occurring.

This is intended as a debugging tool for the developer only. Please refrain from leaving trace_puts scattered around in your code. (Extra memory is used for special buffers that are allocated when trace_puts is used)

0 if nothing was written, positive # if string was. (1 when __trace_bputs is used, strlen(str) when __trace_puts is used)