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  1. 17 Jul, 2018 1 commit
    • Ingo Molnar's avatar
      Merge branch 'for-mingo' of... · ea73a5c6
      Ingo Molnar authored 
      Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu

Pull RCU updates from Paul E. McKenney:

- An optimization and a fix for RCU expedited grace periods, with
  the fix being from Boqun Feng.

- Miscellaneous fixes, including a lockdep-annotation fix from
  Boqun Feng.

- SRCU updates.

- Updates to rcutorture and associated scripting.

- Introduce grace-period sequence numbers to the RCU-bh, RCU-preempt,
  and RCU-sched flavors, replacing the old ->gpnum and ->completed
  pair of fields.  This change allows lockless code to obtain the
  complete grace-period state with a single READ_ONCE(), which is
  needed to maintain tolerable lock contention during the upcoming
  consolidation of the three RCU flavors.  Note that grace-period
  sequence numbers are already used by rcu_barrier(), expedited
  RCU grace periods, and SRCU, and are thus already heavily used
  and well-tested.  Joel Fernandes contributed a number of excellent
  fixes and improvements.

- Clean up some grace-period-reporting loose ends, including
  improving the handling of quiescent states from offline CPUs
  and fixing some false-positive WARN_ON_ONCE() invocations.
  (Strictly speaking, the WARN_ON_ONCE() invocations were quite
  correct, but their invariants were (harmlessly) violated by the
  earlier sloppy handling of quiescent states from offline CPUs.)
  In addition, improve grace-period forward-progress guarantees so
  as to allow removal of fail-safe checks that required otherwise
  needless lock acquisitions.  Finally, add more diagnostics to
  help debug the upcoming consolidation of the RCU-bh, RCU-preempt,
  and RCU-sched flavors.

- Additional miscellaneous fixes, including those contributed by
  Byungchul Park, Mauro Carvalho Chehab, Joe Perches, Joel Fernandes,
  Steven Rostedt, Andrea Parri, and Neil Brown.

- Additional torture-test changes, including several contributed by
  Arnd Bergmann and Joel Fernandes.
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      ea73a5c6
  3. 15 Jul, 2018 2 commits
  5. 14 Jul, 2018 19 commits
  7. 13 Jul, 2018 15 commits
  9. 12 Jul, 2018 3 commits
    • Joel Fernandes (Google)'s avatar
      tracing: Reorder display of TGID to be after PID · f8494fa3
      Joel Fernandes (Google) authored 
      Currently ftrace displays data in trace output like so:

                                       _-----=> irqs-off
                                      / _----=> need-resched
                                     | / _---=> hardirq/softirq
                                     || / _--=> preempt-depth
                                     ||| /     delay
            TASK-PID   CPU    TGID   ||||    TIMESTAMP  FUNCTION
               | |       |      |    ||||       |         |
            bash-1091  [000] ( 1091) d..2    28.313544: sched_switch:

However Android's trace visualization tools expect a slightly different
format due to an out-of-tree patch patch that was been carried for a
decade, notice that the TGID and CPU fields are reversed:

                                       _-----=> irqs-off
                                      / _----=> need-resched
                                     | / _---=> hardirq/softirq
                                     || / _--=> preempt-depth
                                     ||| /     delay
            TASK-PID    TGID   CPU   ||||    TIMESTAMP  FUNCTION
               | |        |      |   ||||       |         |
            bash-1091  ( 1091) [002] d..2    64.965177: sched_switch:

From kernel v4.13 onwards, during which TGID was introduced, tracing
with systrace on all Android kernels will break (most Android kernels
have been on 4.9 with Android patches, so this issues hasn't been seen
yet). From v4.13 onwards things will break.

The chrome browser's tracing tools also embed the systrace viewer which
uses the legacy TGID format and updates to that are known to be
difficult to make.

Considering this, I suggest we make this change to the upstream kernel
and backport it to all Android kernels. I believe this feature is merged
recently enough into the upstream kernel that it shouldn't be a problem.
Also logically, IMO it makes more sense to group the TGID with the
TASK-PID and the CPU after these.

Link: http://lkml.kernel.org/r/20180626000822.113931-1-joel@joelfernandes.org

Cc: jreck@google.com
Cc: tkjos@google.com
Cc: stable@vger.kernel.org
Fixes: 441dae8f ("tracing: Add support for display of tgid in trace output")
Signed-off-by: default avatarJoel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
      f8494fa3
    • Paul E. McKenney's avatar
      Merge branches 'fixes1.2018.07.12b' and 'torture1.2018.07.12b' into HEAD · 18952651
      Paul E. McKenney authored 
      fixes1.2018.07.12b: Post-gp_seq miscellaneous fixes
torture1.2018.07.12b: Post-gp_seq torture-test updates
      18952651
    • Joel Fernandes (Google)'s avatar
      rcutorture: Fix rcu_barrier successes counter · bf5b6435
      Joel Fernandes (Google) authored 
      The rcutorture test module currently increments both successes and error
for the barrier test upon error, which results in misleading statistics
being printed.  This commit therefore changes the code to increment the
success counter only when the test actually passes.

This change was tested by by returning from the barrier callback without
incrementing the callback counter, thus introducing what appeared to
rcutorture to be rcu_barrier() failures.
Signed-off-by: default avatarJoel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      bf5b6435
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