tracing: Add back in rcu_irq_enter/exit_irqson() for rcuidle tracepoints
authorSteven Rostedt (VMware) <rostedt@goodmis.org>
Tue, 4 Sep 2018 20:26:11 +0000 (16:26 -0400)
committerSteven Rostedt (VMware) <rostedt@goodmis.org>
Wed, 5 Sep 2018 15:23:21 +0000 (11:23 -0400)
commit865e63b04e9b2a658d7f26bd13a71dcd964a9118
treedc10dcc23b3aba7e35595809df1be286e8a8cf1b
parent57361846b52bc686112da6ca5368d11210796804
tracing: Add back in rcu_irq_enter/exit_irqson() for rcuidle tracepoints

Borislav reported the following splat:

 =============================
 WARNING: suspicious RCU usage
 4.19.0-rc1+ #1 Not tainted
 -----------------------------
 ./include/linux/rcupdate.h:631 rcu_read_lock() used illegally while idle!
 other info that might help us debug this:

 RCU used illegally from idle CPU!
 rcu_scheduler_active = 2, debug_locks = 1
 RCU used illegally from extended quiescent state!
 1 lock held by swapper/0/0:
  #0: 000000004557ee0e (rcu_read_lock){....}, at: perf_event_output_forward+0x0/0x130

 stack backtrace:
 CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.19.0-rc1+ #1
 Hardware name: LENOVO 2320CTO/2320CTO, BIOS G2ET86WW (2.06 ) 11/13/2012
 Call Trace:
  dump_stack+0x85/0xcb
  perf_event_output_forward+0xf6/0x130
  __perf_event_overflow+0x52/0xe0
  perf_swevent_overflow+0x91/0xb0
  perf_tp_event+0x11a/0x350
  ? find_held_lock+0x2d/0x90
  ? __lock_acquire+0x2ce/0x1350
  ? __lock_acquire+0x2ce/0x1350
  ? retint_kernel+0x2d/0x2d
  ? find_held_lock+0x2d/0x90
  ? tick_nohz_get_sleep_length+0x83/0xb0
  ? perf_trace_cpu+0xbb/0xd0
  ? perf_trace_buf_alloc+0x5a/0xa0
  perf_trace_cpu+0xbb/0xd0
  cpuidle_enter_state+0x185/0x340
  do_idle+0x1eb/0x260
  cpu_startup_entry+0x5f/0x70
  start_kernel+0x49b/0x4a6
  secondary_startup_64+0xa4/0xb0

This is due to the tracepoints moving to SRCU usage which does not require
RCU to be "watching". But perf uses these tracepoints with RCU and expects
it to be. Hence, we still need to add in the rcu_irq_enter/exit_irqson()
calls for "rcuidle" tracepoints. This is a temporary fix until we have SRCU
working in NMI context, and then perf can be converted to use that instead
of normal RCU.

Link: http://lkml.kernel.org/r/20180904162611.6a120068@gandalf.local.home
Cc: x86-ml <x86@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Reported-by: Borislav Petkov <bp@alien8.de>
Tested-by: Borislav Petkov <bp@alien8.de>
Reviewed-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Fixes: e6753f23d961d ("tracepoint: Make rcuidle tracepoint callers use SRCU")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
include/linux/tracepoint.h