Re: [for-next][PATCH 0/5] selftests: ftrace: Tracing updates to allow instance testing

[Steven Rostedt <rostedt@goodmis.org>]

On Wed, 26 Apr 2017 11:07:52 +0900
Namhyung Kim <namhyung@kernel.org> wrote:

> Hi Steve,
> 
> On Tue, Apr 25, 2017 at 09:24:40AM -0400, Steven Rostedt wrote:
> >   git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
> > for-next
> > 
> > Head SHA1: d6322f6cc483bd512efd3360fa76d0286a5b528b
> > 
> > 
> > Steven Rostedt (VMware) (5):
> >       selftests: ftrace: Allow some tests to be run in a tracing instance
> >       selftests: ftrace: Make func_event_triggers and func_traceonoff_triggers tests do instances
> >       selftests: ftrace: Have event tests also run in an tracing instance
> >       selftests: ftrace: Have some basic tests run in a tracing instance too
> >       selftests: ftrace: Allow some event trigger tests to run in an instance  
> 
> Acked-by: Namhyung Kim <namhyung@kernel.org>
> 
> 
> But I saw a warning during the below test.  I used the for-next branch
> but the commit id was different:
> 
> c486bbae781cce337a31cbbbc609f2313ab54542 ("Merge branch
> 'trace/ftrace/core' into trace/ftrace/next").

Yeah, my for-next branch is a merge of urgent and my branch. I don't do
rebases, but this is actually a reset, of a new merge between my two
branches.

> 
> Thanks,
> Namhyung
> 
> 
> [2] Basic test for tracers
> [  908.674961] 
> [  908.675178] ===============================
> [  908.675611] [ ERR: suspicious RCU usage.  ]
> [  908.675922] 4.11.0-rc5kvm+ #230 Tainted: G        W      
> [  908.675922] -------------------------------
> [  908.675922] /home/namhyung/project/linux/include/linux/rcupdate.h:842 rcu_read_lock() used illegally while idle!
> [  908.675922] 
> [  908.675922] other info that might help us debug this:
> [  908.675922] 
> [  908.675922] 
> [  908.675922] RCU used illegally from idle CPU!
> [  908.675922] rcu_scheduler_active = 2, debug_locks = 0
> [  908.675922] RCU used illegally from extended quiescent state!
> [  908.675922] 2 locks held by swapper/0/0:
> [  908.675922]  #0:  (max_trace_lock){......}, at: [<ffffffff81143c33>] check_critical_timing+0xa3/0x150
> [  908.675922]  #1:  (rcu_read_lock){......}, at: [<ffffffff8111f9b5>] __is_insn_slot_addr+0x5/0x120
> [  908.675922] 
> [  908.675922] stack backtrace:
> [  908.675922] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G        W       4.11.0-rc5kvm+ #230
> [  908.675922] Call Trace:
> [  908.675922]  dump_stack+0x68/0x93
> [  908.675922]  lockdep_rcu_suspicious+0xe0/0x100
> [  908.675922]  ? start_kernel+0x3b7/0x3c4
> [  908.675922]  __is_insn_slot_addr+0xe4/0x120
> [  908.675922]  ? start_kernel+0x3b7/0x3c4
> [  908.675922]  __kernel_text_address+0x69/0xb0
> [  908.675922]  ? start_kernel+0x3b7/0x3c4
> [  908.675922]  unwind_get_return_address+0x47/0x60
> [  908.675922]  __save_stack_trace+0x83/0xd0
> [  908.675922]  save_stack_trace+0x1b/0x20
> [  908.675922]  __ftrace_trace_stack+0x22e/0x240
> [  908.675922]  __trace_stack+0x10/0x20
> [  908.675922]  check_critical_timing+0xe9/0x150

Ah, this is a different issue from the stack tracing one. This is irq
tracing. I wonder if we should have that stop latency tracing when RCU
is not functioning.

-- Steve

> [  908.675922]  ? do_idle+0x88/0x120
> [  908.675922]  ? default_idle_call+0x23/0x37
> [  908.675922]  ? do_idle+0x88/0x120
> [  908.675922]  stop_critical_timings+0xcf/0xe0
> [  908.675922]  default_idle_call+0x23/0x37
> [  908.675922]  do_idle+0x88/0x120
> [  908.675922]  cpu_startup_entry+0x1d/0x20
> [  908.675922]  rest_init+0x130/0x140
> [  908.675922]  start_kernel+0x3b7/0x3c4
> [  908.675922]  x86_64_start_reservations+0x2f/0x31
> [  908.675922]  x86_64_start_kernel+0x17d/0x190
> [  908.675922]  start_cpu+0x14/0x14
> [  908.675922]  ? start_cpu+0x14/0x14
> 	[PASS]