Merge branches 'torture.2014.11.03a', 'cpu.2014.11.03a', 'doc.2014.11.13a', 'fixes.2014.11.13a', 'signal.2014.10.29a' and 'rt.2014.10.29a' into HEAD

cpu.2014.11.03a: Changes for per-CPU variables.
doc.2014.11.13a: Documentation updates.
fixes.2014.11.13a: Miscellaneous fixes.
signal.2014.10.29a: Signal changes.
rt.2014.10.29a: Real-time changes.
torture.2014.11.03a: torture-test changes.
This commit is contained in:
Paul E. McKenney
2014-11-13 10:39:04 -08:00
41 changed files with 296 additions and 252 deletions

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@@ -36,7 +36,7 @@ o How can the updater tell when a grace period has completed
executed in user mode, or executed in the idle loop, we can
safely free up that item.
Preemptible variants of RCU (CONFIG_TREE_PREEMPT_RCU) get the
Preemptible variants of RCU (CONFIG_PREEMPT_RCU) get the
same effect, but require that the readers manipulate CPU-local
counters. These counters allow limited types of blocking within
RCU read-side critical sections. SRCU also uses CPU-local
@@ -81,7 +81,7 @@ o I hear that RCU is patented? What is with that?
o I hear that RCU needs work in order to support realtime kernels?
This work is largely completed. Realtime-friendly RCU can be
enabled via the CONFIG_TREE_PREEMPT_RCU kernel configuration
enabled via the CONFIG_PREEMPT_RCU kernel configuration
parameter. However, work is in progress for enabling priority
boosting of preempted RCU read-side critical sections. This is
needed if you have CPU-bound realtime threads.

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@@ -26,12 +26,6 @@ CONFIG_RCU_CPU_STALL_TIMEOUT
Stall-warning messages may be enabled and disabled completely via
/sys/module/rcupdate/parameters/rcu_cpu_stall_suppress.
CONFIG_RCU_CPU_STALL_VERBOSE
This kernel configuration parameter causes the stall warning to
also dump the stacks of any tasks that are blocking the current
RCU-preempt grace period.
CONFIG_RCU_CPU_STALL_INFO
This kernel configuration parameter causes the stall warning to
@@ -77,7 +71,7 @@ This message indicates that CPU 5 detected that it was causing a stall,
and that the stall was affecting RCU-sched. This message will normally be
followed by a stack dump of the offending CPU. On TREE_RCU kernel builds,
RCU and RCU-sched are implemented by the same underlying mechanism,
while on TREE_PREEMPT_RCU kernel builds, RCU is instead implemented
while on PREEMPT_RCU kernel builds, RCU is instead implemented
by rcu_preempt_state.
On the other hand, if the offending CPU fails to print out a stall-warning
@@ -89,7 +83,7 @@ INFO: rcu_bh_state detected stalls on CPUs/tasks: { 3 5 } (detected by 2, 2502 j
This message indicates that CPU 2 detected that CPUs 3 and 5 were both
causing stalls, and that the stall was affecting RCU-bh. This message
will normally be followed by stack dumps for each CPU. Please note that
TREE_PREEMPT_RCU builds can be stalled by tasks as well as by CPUs,
PREEMPT_RCU builds can be stalled by tasks as well as by CPUs,
and that the tasks will be indicated by PID, for example, "P3421".
It is even possible for a rcu_preempt_state stall to be caused by both
CPUs -and- tasks, in which case the offending CPUs and tasks will all
@@ -205,10 +199,10 @@ o A CPU-bound real-time task in a CONFIG_PREEMPT kernel, which might
o A CPU-bound real-time task in a CONFIG_PREEMPT_RT kernel that
is running at a higher priority than the RCU softirq threads.
This will prevent RCU callbacks from ever being invoked,
and in a CONFIG_TREE_PREEMPT_RCU kernel will further prevent
and in a CONFIG_PREEMPT_RCU kernel will further prevent
RCU grace periods from ever completing. Either way, the
system will eventually run out of memory and hang. In the
CONFIG_TREE_PREEMPT_RCU case, you might see stall-warning
CONFIG_PREEMPT_RCU case, you might see stall-warning
messages.
o A hardware or software issue shuts off the scheduler-clock

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@@ -8,7 +8,7 @@ The following sections describe the debugfs files and formats, first
for rcutree and next for rcutiny.
CONFIG_TREE_RCU and CONFIG_TREE_PREEMPT_RCU debugfs Files and Formats
CONFIG_TREE_RCU and CONFIG_PREEMPT_RCU debugfs Files and Formats
These implementations of RCU provide several debugfs directories under the
top-level directory "rcu":
@@ -18,7 +18,7 @@ rcu/rcu_preempt
rcu/rcu_sched
Each directory contains files for the corresponding flavor of RCU.
Note that rcu/rcu_preempt is only present for CONFIG_TREE_PREEMPT_RCU.
Note that rcu/rcu_preempt is only present for CONFIG_PREEMPT_RCU.
For CONFIG_TREE_RCU, the RCU flavor maps onto the RCU-sched flavor,
so that activity for both appears in rcu/rcu_sched.

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@@ -137,7 +137,7 @@ rcu_read_lock()
Used by a reader to inform the reclaimer that the reader is
entering an RCU read-side critical section. It is illegal
to block while in an RCU read-side critical section, though
kernels built with CONFIG_TREE_PREEMPT_RCU can preempt RCU
kernels built with CONFIG_PREEMPT_RCU can preempt RCU
read-side critical sections. Any RCU-protected data structure
accessed during an RCU read-side critical section is guaranteed to
remain unreclaimed for the full duration of that critical section.