linux-toradex.git/include/linux/rcupdate.h, branch v2.6.34

rcu: create rcu_my_thread_group_empty() wrapper

2010-05-06T16:28:41+00:00

Some RCU-lockdep splat repairs need to know whether they are running
in a single-threaded process.  Unfortunately, the thread_group_empty()
primitive is defined in sched.h, and can induce #include hell.  This
commit therefore introduces a rcu_my_thread_group_empty() wrapper that
is defined in rcupdate.c, thus avoiding the need to include sched.h
everywhere.

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

rcu: Make RCU lockdep check the lockdep_recursion variable

2010-04-19T06:37:19+00:00

The lockdep facility temporarily disables lockdep checking by
incrementing the current->lockdep_recursion variable.  Such
disabling happens in NMIs and in other situations where lockdep
might expect to recurse on itself.

This patch therefore checks current->lockdep_recursion, disabling RCU
lockdep splats when this variable is non-zero.  In addition, this patch
removes the "likely()", as suggested by Lai Jiangshan.

Reported-by: Frederic Weisbecker 
Reported-by: David Miller 
Tested-by: Frederic Weisbecker 
Signed-off-by: Paul E. McKenney 
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
Cc: eric.dumazet@gmail.com
LKML-Reference: <20100415195039.GA22623@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar

rcu: Better explain the condition parameter of rcu_dereference_check()

2010-04-14T10:20:04+00:00

Better explain the condition parameter of
rcu_dereference_check() that describes the conditions under
which the dereference is permitted to take place (and
incorporate Yong Zhang's suggestion).  This condition is only
checked under lockdep proving.

Signed-off-by: David Howells 
Signed-off-by: Paul E. McKenney 
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: eric.dumazet@gmail.com
LKML-Reference: <1270852752-25278-2-git-send-email-paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar

rcu: Add rcu_access_pointer and rcu_dereference_protected

2010-04-14T10:19:51+00:00

This patch adds variants of rcu_dereference() that handle
situations where the RCU-protected data structure cannot change,
perhaps due to our holding the update-side lock, or where the
RCU-protected pointer is only to be fetched, not dereferenced.
These are needed due to some performance concerns with using
rcu_dereference() where it is not required, aside from the need
for lockdep/sparse checking.

The new rcu_access_pointer() primitive is for the case where the
pointer is be fetch and not dereferenced.  This primitive may be
used without protection, RCU or otherwise, due to the fact that
it uses ACCESS_ONCE().

The new rcu_dereference_protected() primitive is for the case
where updates are prevented, for example, due to holding the
update-side lock.  This primitive does neither ACCESS_ONCE() nor
smp_read_barrier_depends(), so can only be used when updates are
somehow prevented.

Suggested-by: David Howells 
Signed-off-by: Paul E. McKenney 
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
Cc: eric.dumazet@gmail.com
LKML-Reference: <1270852752-25278-1-git-send-email-paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar

rcu: Fix local_irq_disable() CONFIG_PROVE_RCU=y false positives

2010-03-18T20:25:32+00:00

It is documented that local_irq_disable() also delimits RCU_SCHED
read-site critical sections.

See the document of synchronize_sched() or
Documentation/RCU/whatisRCU.txt.

So we have to test irqs_disabled() in rcu_read_lock_sched_held().
Otherwise rcu-lockdep brings incorrect complaint.

Signed-off-by: Lai Jiangshan 
Signed-off-by: Paul E. McKenney 
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
Cc: eric.dumazet@gmail.com
LKML-Reference: <1268940334-10892-1-git-send-email-paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar

rcu: Make rcu_read_lock_bh_held() allow for disabled BH

2010-03-16T08:57:49+00:00

Disabling BH can stand in for rcu_read_lock_bh(), and this patch
updates rcu_read_lock_bh_held() to allow for this.  In order to
avoid include-file hell, this function is moved out of line to
kernel/rcupdate.c.

This fixes a false positive RCU warning.

Reported-by: Arnd Bergmann 
Reported-by: Eric Dumazet 
Signed-off-by: Paul E. McKenney 
Acked-by: Lai Jiangshan 
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <20100316000343.GA25857@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar

Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

2010-03-13T22:43:01+00:00

* 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  locking: Make sparse work with inline spinlocks and rwlocks
  x86/mce: Fix RCU lockdep splats
  rcu: Increase RCU CPU stall timeouts if PROVE_RCU
  ftrace: Replace read_barrier_depends() with rcu_dereference_raw()
  rcu: Suppress RCU lockdep warnings during early boot
  rcu, ftrace: Fix RCU lockdep splat in ftrace_perf_buf_prepare()
  rcu: Suppress __mpol_dup() false positive from RCU lockdep
  rcu: Make rcu_read_lock_sched_held() handle !PREEMPT
  rcu: Add control variables to lockdep_rcu_dereference() diagnostics
  rcu, cgroup: Relax the check in task_subsys_state() as early boot is now handled by lockdep-RCU
  rcu: Use wrapper function instead of exporting tasklist_lock
  sched, rcu: Fix rcu_dereference() for RCU-lockdep
  rcu: Make task_subsys_state() RCU-lockdep checks handle boot-time use
  rcu: Fix holdoff for accelerated GPs for last non-dynticked CPU
  x86/gart: Unexport gart_iommu_aperture

Fix trivial conflicts in kernel/trace/ftrace.c

sysctl extern cleanup: rcu

2010-03-12T23:53:08+00:00

Extern declarations in sysctl.c should be moved to their own header file,
and then include them in relavant .c files.

Move rcutorture_runnable extern declaration to linux/rcupdate.h

Signed-off-by: Dave Young 
Acked-by: Josh Triplett 
Reviewed-by: "Paul E. McKenney" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

rcu: Suppress RCU lockdep warnings during early boot

2010-03-04T11:09:19+00:00

RCU is used during very early boot, before RCU and lockdep have
been initialized.  So make the underlying primitives
(rcu_read_lock_held(), rcu_read_lock_bh_held(),
rcu_read_lock_sched_held(), and rcu_dereference_check()) check
for early boot via the rcu_scheduler_active flag.  This will
suppress false positives.

Also introduce a debug_lockdep_rcu_enabled() static inline
helper function, which tags the CONTINUE_PROVE_RCU case as
likely(), as suggested by Ingo Molnar.

Signed-off-by: Paul E. McKenney 
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <1267631219-8713-2-git-send-email-paulmck@linux.vnet.ibm.com>
[ v2: removed incomplete debug_lockdep_rcu_update() bits ]
Signed-off-by: Ingo Molnar

rcu: Make rcu_read_lock_sched_held() handle !PREEMPT

2010-03-04T11:07:33+00:00

The rcu_read_lock_sched_held() needs to unconditionally return
the value "1" in a !PREEMPT kernel, because under !PREEMPT,
-all- kernel code is implicitly preempt-disabled.  This patch
makes this happen.

Signed-off-by: Paul E. McKenney 
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <1267667418-32233-1-git-send-email-paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar