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

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Pull RCU changes from Ingo Molnar:
 "This is the v3.5 RCU tree from Paul E.  McKenney:

 1) A set of improvements and fixes to the RCU_FAST_NO_HZ feature (with
    more on the way for 3.6).  Posted to LKML:
       https://lkml.org/lkml/2012/4/23/324 (commits 1-3 and 5),
       https://lkml.org/lkml/2012/4/16/611 (commit 4),
       https://lkml.org/lkml/2012/4/30/390 (commit 6), and
       https://lkml.org/lkml/2012/5/4/410 (commit 7, combined with
       the other commits for the convenience of the tester).

 2) Changes to make rcu_barrier() avoid disrupting execution of CPUs
    that have no RCU callbacks.  Posted to LKML:
       https://lkml.org/lkml/2012/4/23/322.

 3) A couple of commits that improve the efficiency of the interaction
    between preemptible RCU and the scheduler, these two being all that
    survived an abortive attempt to allow preemptible RCU's
    __rcu_read_lock() to be inlined.  The full set was posted to LKML at
    https://lkml.org/lkml/2012/4/14/143, and the first and third patches
    of that set remain.

 4) Lai Jiangshan's algorithmic implementation of SRCU, which includes
    call_srcu() and srcu_barrier().  A major feature of this new
    implementation is that synchronize_srcu() no longer disturbs the
    execution of other CPUs.  This work is based on earlier
    implementations by Peter Zijlstra and Paul E.  McKenney.  Posted to
    LKML: https://lkml.org/lkml/2012/2/22/82.

 5) A number of miscellaneous bug fixes and improvements which were
    posted to LKML at: https://lkml.org/lkml/2012/4/23/353 with
    subsequent updates posted to LKML."

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (32 commits)
  rcu: Make rcu_barrier() less disruptive
  rcu: Explicitly initialize RCU_FAST_NO_HZ per-CPU variables
  rcu: Make RCU_FAST_NO_HZ handle timer migration
  rcu: Update RCU maintainership
  rcu: Make exit_rcu() more precise and consolidate
  rcu: Move PREEMPT_RCU preemption to switch_to() invocation
  rcu: Ensure that RCU_FAST_NO_HZ timers expire on correct CPU
  rcu: Add rcutorture test for call_srcu()
  rcu: Implement per-domain single-threaded call_srcu() state machine
  rcu: Use single value to handle expedited SRCU grace periods
  rcu: Improve srcu_readers_active_idx()'s cache locality
  rcu: Remove unused srcu_barrier()
  rcu: Implement a variant of Peter's SRCU algorithm
  rcu: Improve SRCU's wait_idx() comments
  rcu: Flip ->completed only once per SRCU grace period
  rcu: Increment upper bit only for srcu_read_lock()
  rcu: Remove fast check path from __synchronize_srcu()
  rcu: Direct algorithmic SRCU implementation
  rcu: Introduce rcutorture testing for rcu_barrier()
  timer: Fix mod_timer_pinned() header comment
  ...
This commit is contained in:
Linus Torvalds
2012-05-21 19:26:51 -07:00
parent 5ec29e3149 2d84e023cb
commit 226da0dbc8
23 changed files with 1358 additions and 353 deletions
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50
init/Kconfig
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@@ -458,6 +458,33 @@ config RCU_FANOUT
Select a specific number if testing RCU itself.
Take the default if unsure.
config RCU_FANOUT_LEAF
int "Tree-based hierarchical RCU leaf-level fanout value"
range 2 RCU_FANOUT if 64BIT
range 2 RCU_FANOUT if !64BIT
depends on TREE_RCU || TREE_PREEMPT_RCU
default 16
help
This option controls the leaf-level fanout of hierarchical
implementations of RCU, and allows trading off cache misses
against lock contention. Systems that synchronize their
scheduling-clock interrupts for energy-efficiency reasons will
want the default because the smaller leaf-level fanout keeps
lock contention levels acceptably low. Very large systems
(hundreds or thousands of CPUs) will instead want to set this
value to the maximum value possible in order to reduce the
number of cache misses incurred during RCU's grace-period
initialization. These systems tend to run CPU-bound, and thus
are not helped by synchronized interrupts, and thus tend to
skew them, which reduces lock contention enough that large
leaf-level fanouts work well.
Select a specific number if testing RCU itself.
Select the maximum permissible value for large systems.
Take the default if unsure.
config RCU_FANOUT_EXACT
bool "Disable tree-based hierarchical RCU auto-balancing"
depends on TREE_RCU || TREE_PREEMPT_RCU
@@ -515,10 +542,25 @@ config RCU_BOOST_PRIO
depends on RCU_BOOST
default 1
help
This option specifies the real-time priority to which preempted
RCU readers are to be boosted. If you are working with CPU-bound
real-time applications, you should specify a priority higher then
the highest-priority CPU-bound application.
This option specifies the real-time priority to which long-term
preempted RCU readers are to be boosted. If you are working
with a real-time application that has one or more CPU-bound
threads running at a real-time priority level, you should set
RCU_BOOST_PRIO to a priority higher then the highest-priority
real-time CPU-bound thread. The default RCU_BOOST_PRIO value
of 1 is appropriate in the common case, which is real-time
applications that do not have any CPU-bound threads.
Some real-time applications might not have a single real-time
thread that saturates a given CPU, but instead might have
multiple real-time threads that, taken together, fully utilize
that CPU. In this case, you should set RCU_BOOST_PRIO to
a priority higher than the lowest-priority thread that is
conspiring to prevent the CPU from running any non-real-time
tasks. For example, if one thread at priority 10 and another
thread at priority 5 are between themselves fully consuming
the CPU time on a given CPU, then RCU_BOOST_PRIO should be
set to priority 6 or higher.
Specify the real-time priority, or take the default if unsure.