• Linus Torvalds's avatar
    Merge tag 'trace-3.19-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace · a7c180aa
    Linus Torvalds authored
    Pull tracing updates from Steven Rostedt:
     "As the merge window is still open, and this code was not as complex as
      I thought it might be.  I'm pushing this in now.
    
      This will allow Thomas to debug his irq work for 3.20.
    
      This adds two new features:
    
      1) Allow traceopoints to be enabled right after mm_init().
    
         By passing in the trace_event= kernel command line parameter,
         tracepoints can be enabled at boot up.  For debugging things like
         the initialization of interrupts, it is needed to have tracepoints
         enabled very early.  People have asked about this before and this
         has been on my todo list.  As it can be helpful for Thomas to debug
         his upcoming 3.20 IRQ work, I'm pushing this now.  This way he can
         add tracepoints into the IRQ set up and have users enable them when
         things go wrong.
    
      2) Have the tracepoints printed via printk() (the console) when they
         are triggered.
    
         If the irq code locks up or reboots the box, having the tracepoint
         output go into the kernel ring buffer is useless for debugging.
         But being able to add the tp_printk kernel command line option
         along with the trace_event= option will have these tracepoints
         printed as they occur, and that can be really useful for debugging
         early lock up or reboot problems.
    
      This code is not that intrusive and it passed all my tests.  Thomas
      tried them out too and it works for his needs.
    
       Link: http://lkml.kernel.org/r/20141214201609.126831471@goodmis.org"
    
    * tag 'trace-3.19-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
      tracing: Add tp_printk cmdline to have tracepoints go to printk()
      tracing: Move enabling tracepoints to just after rcu_init()
    a7c180aa
trace_events.c 61.2 KB