linux-toradex.git/kernel/rcupdate.c, branch v3.10.2

Merge branches 'doctorture.2013.01.29a', 'fixes.2013.01.26a', 'tagcb.2013.01.24a' and 'tiny.2013.01.29b' into HEAD

2013-01-29T06:25:21+00:00

doctorture.2013.01.11a: Changes to rcutorture and to RCU documentation.

fixes.2013.01.26a: Miscellaneous fixes.

tagcb.2013.01.24a: Tag RCU callbacks with grace-period number to
	simplify callback advancement.

tiny.2013.01.29b: Enhancements to uniprocessor handling in tiny RCU.

rcu: Provide RCU CPU stall warnings for tiny RCU

2013-01-29T06:06:21+00:00

Tiny RCU has historically omitted RCU CPU stall warnings in order to
reduce memory requirements, however, lack of these warnings caused
Thomas Gleixner some debugging pain recently.  Therefore, this commit
adds RCU CPU stall warnings to tiny RCU if RCU_TRACE=y.  This keeps
the memory footprint small, while still enabling CPU stall warnings
in kernels built to enable them.

Updated to include Josh Triplett's suggested use of RCU_STALL_COMMON
config variable to simplify #if expressions.

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

rcu: Reduce rcutorture tracing

2013-01-08T22:14:55+00:00

Currently, rcutorture traces every read-side access.  This can be
problematic because even a two-minute rcutorture run on a two-CPU system
can generate 28,853,363 reads.  Normally, only a failing read is of
interest, so this commit traces adjusts rcutorture's tracing to only
trace failing reads.  The resulting event tracing records the time
and the ->completed value captured at the beginning of the RCU read-side
critical section, allowing correlation with other event-tracing messages.

Signed-off-by: Paul E. McKenney 
Signed-off-by: Paul E. McKenney 
Reviewed-by: Josh Triplett 
[ paulmck: Add fix to build problem located by Randy Dunlap based on
  diagnosis by Steven Rostedt. ]

rcu: Add a module parameter to force use of expedited RCU primitives

2012-10-23T21:54:08+00:00

There have been some embedded applications that would benefit from
use of expedited grace-period primitives.  In some ways, this is
similar to synchronize_net() doing either a normal or an expedited
grace period depending on lock state, but with control outside of
the kernel.

This commit therefore adds rcu_expedited boot and sysfs parameters
that cause the kernel to substitute expedited primitives for the
normal grace-period primitives.

[ paulmck: Add trace/event/rcu.h to kernel/srcu.c to avoid build error.
	   Get rid of infinite loop through contention path.]

Signed-off-by: Antti P Miettinen 
Signed-off-by: Paul E. McKenney

rcu: Add PROVE_RCU_DELAY to provoke difficult races

2012-09-23T14:42:49+00:00

There have been some recent bugs that were triggered only when
preemptible RCU's __rcu_read_unlock() was preempted just after setting
->rcu_read_lock_nesting to INT_MIN, which is a low-probability event.
Therefore, reproducing those bugs (to say nothing of gaining confidence
in alleged fixes) was quite difficult.  This commit therefore creates
a new debug-only RCU kernel config option that forces a short delay
in __rcu_read_unlock() to increase the probability of those sorts of
bugs occurring.

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

rcu: Consolidate tree/tiny __rcu_read_{,un}lock() implementations

2012-07-02T19:34:23+00:00

The CONFIG_TREE_PREEMPT_RCU and CONFIG_TINY_PREEMPT_RCU versions of
__rcu_read_lock() and __rcu_read_unlock() are identical, so this commit
consolidates them into kernel/rcupdate.h.

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

rcu: Make exit_rcu() more precise and consolidate

2012-05-02T21:48:27+00:00

When running preemptible RCU, if a task exits in an RCU read-side
critical section having blocked within that same RCU read-side critical
section, the task must be removed from the list of tasks blocking a
grace period (perhaps the current grace period, perhaps the next grace
period, depending on timing).  The exit() path invokes exit_rcu() to
do this cleanup.

However, the current implementation of exit_rcu() needlessly does the
cleanup even if the task did not block within the current RCU read-side
critical section, which wastes time and needlessly increases the size
of the state space.  Fix this by only doing the cleanup if the current
task is actually on the list of tasks blocking some grace period.

While we are at it, consolidate the two identical exit_rcu() functions
into a single function.

Signed-off-by: Paul E. McKenney 
Signed-off-by: Paul E. McKenney 
Tested-by: Linus Torvalds 

Conflicts:

	kernel/rcupdate.c

rcu: Check for illegal use of RCU from offlined CPUs

2012-02-21T17:06:03+00:00

Although it is legal to use RCU during early boot, it is anything
but legal to use RCU at runtime from an offlined CPU.  After all, RCU
explicitly ignores offlined CPUs.  This commit therefore adds checks
for runtime use of RCU from offlined CPUs.

These checks are not perfect, in particular, they can be subverted
through use of things like rcu_dereference_raw().  Note that it is not
possible to put checks in rcu_read_lock() and friends due to the fact
that these primitives are used in code that might be used under either
RCU or lock-based protection, which means that checking rcu_read_lock()
gets you fat piles of false positives.

Signed-off-by: Paul E. McKenney 
Signed-off-by: Paul E. McKenney

rcu: Detect illegal rcu dereference in extended quiescent state

2011-12-11T18:31:30+00:00

Report that none of the rcu read lock maps are held while in an RCU
extended quiescent state (the section between rcu_idle_enter()
and rcu_idle_exit()). This helps detect any use of rcu_dereference()
and friends from within the section in idle where RCU is not allowed.

This way we can guarantee an extended quiescent window where the CPU
can be put in dyntick idle mode or can simply aoid to be part of any
global grace period completion while in the idle loop.

Uses of RCU from such mode are totally ignored by RCU, hence the
importance of these checks.

Signed-off-by: Frederic Weisbecker 
Cc: Paul E. McKenney 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Lai Jiangshan 
Signed-off-by: Paul E. McKenney 
Reviewed-by: Josh Triplett

rcu: Add failure tracing to rcutorture

2011-12-11T18:31:26+00:00

Trace the rcutorture RCU accesses and dump the trace buffer when the
first failure is detected.

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