linux-stable.git/kernel/rcu.h, branch master

rcu: Move RCU-related source code to kernel/rcu directory

2013-10-15T19:53:31+00:00

Signed-off-by: Paul E. McKenney 
Reviewed-by: Ingo Molnar

rcu: Have rcutiny tracepoints use tracepoint_string()

2013-09-23T16:15:31+00:00

This commit extends the work done in f7f7bac9 (rcu: Have the RCU
tracepoints use the tracepoint_string infrastructure) to cover rcutiny.

Signed-off-by: Paul E. McKenney 
Cc: Steven Rostedt

rcu: Make call_rcu() leak callbacks for debug-object errors

2013-08-19T00:40:03+00:00

If someone does a duplicate call_rcu(), the worst thing the second
call_rcu() could do would be to actually queue the callback the second
time because doing so corrupts whatever list the callback was already
queued on.  This commit therefore makes __call_rcu() check the new
return value from debug-objects and leak the callback upon error.
This commit also substitutes rcu_leak_callback() for whatever callback
function was previously in place in order to avoid freeing the callback
out from under any readers that might still be referencing it.

These changes increase the probability that the debug-objects error
messages will actually make it somewhere visible.

Signed-off-by: Paul E. McKenney 
Cc: Mathieu Desnoyers 
Cc: Sedat Dilek 
Cc: Davidlohr Bueso 
Cc: Rik van Riel 
Cc: Thomas Gleixner 
Cc: Linus Torvalds 
Tested-by: Sedat Dilek 
Reviewed-by: Josh Triplett

rcu: Add const annotation to char * for RCU tracepoints and functions

2013-07-29T21:07:49+00:00

All the RCU tracepoints and functions that reference char pointers do
so with just 'char *' even though they do not modify the contents of
the string itself. This will cause warnings if a const char * is used
in one of these functions.

The RCU tracepoints store the pointer to the string to refer back to them
when the trace output is displayed. As this can be minutes, hours or
even days later, those strings had better be constant.

This change also opens the door to allow the RCU tracepoint strings and
their addresses to be exported so that userspace tracing tools can
translate the contents of the pointers of the RCU tracepoints.

Signed-off-by: Steven Rostedt

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: 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: Allow nesting of rcu_idle_enter() and rcu_idle_exit()

2012-02-21T17:06:12+00:00

Use of RCU in the idle loop is incorrect, quite a few instances of
just that have made their way into mainline, primarily event tracing.
The problem with RCU read-side critical sections on CPUs that RCU believes
to be idle is that RCU is completely ignoring the CPU, along with any
attempts and RCU read-side critical sections.

The approaches of eliminating the offending uses and of pushing the
definition of idle down beyond the offending uses have both proved
impractical.  The new approach is to encapsulate offending uses of RCU
with rcu_idle_exit() and rcu_idle_enter(), but this requires nesting
for code that is invoked both during idle and and during normal execution.
Therefore, this commit modifies rcu_idle_enter() and rcu_idle_exit() to
permit nesting.

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

rcu: Remove redundant check for rcu_head misalignment

2012-02-21T17:06:11+00:00

There is now an unconditional check for rcu_head misalignment in
__call_rcu(), so remove the old conditional one in debug_rcu_head_queue().

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

rcu: Avoid waking up CPUs having only kfree_rcu() callbacks

2012-02-21T17:03:25+00:00

When CONFIG_RCU_FAST_NO_HZ is enabled, RCU will allow a given CPU to
enter dyntick-idle mode even if it still has RCU callbacks queued.
RCU avoids system hangs in this case by scheduling a timer for several
jiffies in the future.  However, if all of the callbacks on that CPU
are from kfree_rcu(), there is no reason to wake the CPU up, as it is
not a problem to defer freeing of memory.

This commit therefore tracks the number of callbacks on a given CPU
that are from kfree_rcu(), and avoids scheduling the timer if all of
a given CPU's callbacks are from kfree_rcu().

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

rcu: Deconfuse dynticks entry-exit tracing

2011-12-11T18:31:42+00:00

The trace_rcu_dyntick() trace event did not print both the old and
the new value of the nesting level, and furthermore printed only
the low-order 32 bits of it.  This could result in some confusion
when interpreting trace-event dumps, so this commit prints both
the old and the new value, prints the full 64 bits, and also selects
the process-entry/exit increment to print nicely in hexadecimal.

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