linux.git/include/linux/rcupdate.h, branch v3.16-rc5

rcu: Provide API to suppress stall warnings while sysrc runs

2014-05-19T17:52:04+00:00

Some sysrq handlers can run for a long time, because they dump a lot
of data onto a serial console. Having RCU stall warnings pop up in
the middle of them only makes the problem worse.

This commit provides rcu_sysrq_start() and rcu_sysrq_end() APIs to
temporarily suppress RCU CPU stall warnings while a sysrq request is
handled.

Signed-off-by: Rik van Riel 
[ paulmck: Fix TINY_RCU build error. ]
Signed-off-by: Paul E. McKenney

Merge branches 'doc.2014.04.29a', 'fixes.2014.04.29a' and 'torture.2014.05.14a' into HEAD

2014-05-14T17:57:31+00:00

doc.2014.04.29a:  Documentation updates.
fixes.2014.04.29a:  Miscellaneous fixes.
torture.2014.05.14a:  RCU/Lock torture tests.

sched,rcu: Make cond_resched() report RCU quiescent states

2014-05-14T16:46:11+00:00

Given a CPU running a loop containing cond_resched(), with no
other tasks runnable on that CPU, RCU will eventually report RCU
CPU stall warnings due to lack of quiescent states.  Fortunately,
every call to cond_resched() is a perfectly good quiescent state.
Unfortunately, invoking rcu_note_context_switch() is a bit heavyweight
for cond_resched(), especially given the need to disable preemption,
and, for RCU-preempt, interrupts as well.

This commit therefore maintains a per-CPU counter that causes
cond_resched(), cond_resched_lock(), and cond_resched_softirq() to call
rcu_note_context_switch(), but only about once per 256 invocations.
This ratio was chosen in keeping with the relative time constants of
RCU grace periods.

Signed-off-by: Paul E. McKenney 
Reviewed-by: Josh Triplett

rcutorture: Add forward-progress checking for writer

2014-05-13T18:18:18+00:00

The rcutorture output currently does not distinguish between stalls in
the RCU implementation and stalls in the rcu_torture_writer() kthreads.
This commit therefore adds some diagnostics to help distinguish between
these two conditions, at least for the non-SRCU implementations.  (SRCU
does not provide evidence of update-side forward progress by design.)

Signed-off-by: Paul E. McKenney

rcu: Document RCU_INIT_POINTER()'s lack of ordering guarantees

2014-04-29T15:45:13+00:00

Although rcu_assign_pointer() provides ordering guarantees,
RCU_INIT_POINTER() does not.  This commit makes that explicit
in the docbook comment header.

Reported-by: Lai Jiangshan 
Signed-off-by: Paul E. McKenney 
Reviewed-by: Josh Triplett

rcu: Remove "extern" from function declaration in include/linux/rcupdate.h

2014-04-29T15:44:33+00:00

Because functions have the extern storage class specifier by default,
this keyword can be removed. It is redundant to use it explicitly.

Signed-off-by: Iulia Manda 
Signed-off-by: Paul E. McKenney 
Reviewed-by: Josh Triplett

Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2014-03-31T18:05:24+00:00

Pull RCU updates from Ingo Molnar:
 "Main changes:

   - Torture-test changes, including refactoring of rcutorture and
     introduction of a vestigial locktorture.

   - Real-time latency fixes.

   - Documentation updates.

   - Miscellaneous fixes"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (77 commits)
  rcu: Provide grace-period piggybacking API
  rcu: Ensure kernel/rcu/rcu.h can be sourced/used stand-alone
  rcu: Fix sparse warning for rcu_expedited from kernel/ksysfs.c
  notifier: Substitute rcu_access_pointer() for rcu_dereference_raw()
  Documentation/memory-barriers.txt: Clarify release/acquire ordering
  rcutorture: Save kvm.sh output to log
  rcutorture: Add a lock_busted to test the test
  rcutorture: Place kvm-test-1-run.sh output into res directory
  rcutorture: Rename TREE_RCU-Kconfig.txt
  locktorture: Add kvm-recheck.sh plug-in for locktorture
  rcutorture: Gracefully handle NULL cleanup hooks
  locktorture: Add vestigial locktorture configuration
  rcutorture: Introduce "rcu" directory level underneath configs
  rcutorture: Rename kvm-test-1-rcu.sh
  rcutorture: Remove RCU dependencies from ver_functions.sh API
  rcutorture: Create CFcommon file for common Kconfig parameters
  rcutorture: Create config files for scripted test-the-test testing
  rcutorture: Add an rcu_busted to test the test
  locktorture: Add a lock-torture kernel module
  rcutorture: Abstract kvm-recheck.sh
  ...

Merge branches 'doc.2014.02.24a', 'fixes.2014.02.26a' and 'rt.2014.02.17b' into HEAD

2014-02-26T14:36:09+00:00

doc.2014.02.24a: Documentation changes
fixes.2014.02.26a: Miscellaneous fixes
rt.2014.02.17b: Response-time-related changes

rcu: Fix sparse warning for rcu_expedited from kernel/ksysfs.c

2014-02-26T14:35:16+00:00

This commit fixes the follwoing warning:

kernel/ksysfs.c:143:5: warning: symbol 'rcu_expedited' was not declared. Should it be static?

Signed-off-by: Paul Gortmaker 
[ paulmck: Moved the declaration to include/linux/rcupdate.h to avoid
	   including the RCU-internal rcu.h file outside of RCU. ]
Signed-off-by: Paul E. McKenney 
Reviewed-by: Josh Triplett

rcu: Optimize rcu_needs_cpu() for RCU_NOCB_CPU_ALL

2014-02-18T00:03:09+00:00

If CONFIG_RCU_NOCB_CPU_ALL=y, then rcu_needs_cpu() will always
return false, however, the current version nevertheless checks
for RCU callbacks.  This commit therefore creates a static inline
implementation of rcu_needs_cpu() that unconditionally returns false
when CONFIG_RCU_NOCB_CPU_ALL=y.

Signed-off-by: Paul E. McKenney 
Reviewed-by: Josh Triplett