binder: add transaction latency tracer

[Frankie Chang]

Change from v11:
  - rebase.

Change from v10:
  - replace timespec64 with ktime_t.
  - fix build warning.

Change from v9:
  - rename timestamp to ts in binder_internal.h for conciseness.
  - change timeval to timespec64 in binder_internal.h

Change from v8:
  - change rtc_time_to_tm to rtc_time64_to_tm.
  - change timeval to __kernel_old_timeval due to 
    https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c766d1472c70d25ad475cf56042af1652e792b23
  - export tracepoint symbol for binder_txn_latency_* which binder_transaction_latency_tracer to be ko needed.

Change from v7:
  - Use the passed-in values instead of accessing via t->from/to_proc/to_thread
    for trace_binder_txn_latency_free, when trace_binder_txn_latency_free_enable() return true.
  - make a helper function to do the above.

Change from v6:
  - change CONFIG_BINDER_TRANSACTION_LATENCY_TRACKING type from bool to tristate
  - add comments to @timestamp and @tv under struct binder_transaction
  - make binder_txn_latency threshold configurable
  - enhance lock protection

Change from v5:
  - change config name to the proper one, CONFIG_BINDER_TRANSACTION_LATENCY_TRACKING.
  - change tracepoint name to more descriptive one, trace_binder_txn_latency_(alloc|info|free)
  - enhance some lock protection.

Change from v4:
  - split up into patch series.

Change from v3:
  - use tracepoints for binder_update_info and print_binder_transaction_ext,
    instead of custom registration functions.

Change from v2:
  - create transaction latency module to monitor slow transaction.

Change from v1:
  - first patchset.


Frankie.Chang (3):
  binder: move structs from core file to header file
  binder: add trace at free transaction.
  binder: add transaction latency tracer

 drivers/android/Kconfig                 |   8 +
 drivers/android/Makefile                |   1 +
 drivers/android/binder.c                | 430 ++----------------------
 drivers/android/binder_internal.h       | 419 +++++++++++++++++++++++
 drivers/android/binder_latency_tracer.c | 107 ++++++
 drivers/android/binder_trace.h          |  49 +++
 6 files changed, 608 insertions(+), 406 deletions(-)
 create mode 100644 drivers/android/binder_latency_tracer.c