[for-linus][PATCH 0/5] tracing: Fixes for 7.0

[Steven Rostedt <rostedt@kernel.org>]

tracing fixes for 7.0:

- Revert "tracing: Remove pid in task_rename tracing output"

  A change was made to remove the pid field from the task_rename event
  because it was thought that it was always done for the current task and
  recording the pid would be redundant. This turned out to be incorrect and
  there are a few corner casse where this is not true and caused some
  regressions in tooling.

- Fix the reading from user space for migration

  The reading of user space uses a seq lock type of logic where it uses a
  per-cpu temporary buffer and disables migration, then enables preemption,
  does the copy from user space, disables preemption, enables migration and
  checks if there was any schedule switches while preemption was enabled. If
  there was a context switch, then it is considered that the per-cpu buffer
  could be corrupted and it tries again. There's a protection check that
  tests if it takes a hundred tries it issues a warning and exits out to
  prevent a live lock.

  This was triggered because the task was selected by the load balancer to
  be migrated to another CPU, every time preemption is enabled the migration
  task would schedule in try to migrate the task but can't because migration
  is enabled and let it run again. This caused the scheduler to schedule out
  the task every time it enabled preemption and made the loop never exit
  (until the 100 iteration test triggered).

  Fix this by enabling and disabling preemption and keeping migration
  enabled on a failure. This will let the migration thread to migrate the
  task and the copy from user space will likely pass on the next iteration.

- Fix trace_marker copy option freeing

  The "copy_trace_marker" option allows an tracing instance to get a copy of
  a write to the trace_marker file of the top level instance. This is
  managed by a link list protected by RCU. When an instance is removed, a
  check is made if the option is set, and if so synchronized_rcu() is
  called. The problem is that an iteration is made to reset all the flags to
  what they were when the instance was created (to perform clean ups) was
  done before the check of the copy_trace_marker option and that option was
  cleared, so the synchronize_rcu() was never called.

  Move the clearing of all the flags after the check of copy_trace_marker to
  do synchronize_rcu() so that the option is still set if it was before and
  the synchronization is performed.

- Fix entries setting when validating the persistent ring buffer

  When validating the persistent ring buffer on boot up, the number of
  events per sub-buffer is added to the sub-buffer meta page. The validator
  was updating cpu_buffer->head_page (the first sub-buffer of the per-cpu
  buffer) and not the "head_page" variable that was iterating the
  sub-buffers. This was causing the first sub-buffer to be assigned the
  entries for each sub-buffer and not the sub-buffer that was supposed to be
  updated.

- Use "hash" value to update the direct callers

  When updating the ftrace direct direct callers it assigned a temporary
  callback to all the callback functions of the ftrace ops and not just the
  functions represented by the passed in hash. This causes an unnecessary
  slow down of the functions of the ftrace_ops that is not being modified.
  Only update the functions that are going to be modified to call the ftrace
  loop function so that the update can be made on those functions.

  git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git
trace/fixes

Head SHA1: 50b35c9e50a865600344ab1d8f9a8b3384d7e63d


Jiri Olsa (1):
      ftrace: Use hash argument for tmp_ops in update_ftrace_direct_mod

Masami Hiramatsu (Google) (1):
      ring-buffer: Fix to update per-subbuf entries of persistent ring buffer

Steven Rostedt (2):
      tracing: Fix failure to read user space from system call trace events
      tracing: Fix trace_marker copy link list updates

Xuewen Yan (1):
      tracing: Revert "tracing: Remove pid in task_rename tracing output"

----
 include/trace/events/task.h |  7 +++++--
 kernel/trace/ftrace.c       |  4 ++--
 kernel/trace/ring_buffer.c  |  2 +-
 kernel/trace/trace.c        | 36 +++++++++++++++++++++++++++---------
 4 files changed, 35 insertions(+), 14 deletions(-)