Commit Graph

60 Commits

Author SHA1 Message Date
Paul E. McKenney
d0ec774cb2 rcu: Move rcu_barrier() to rcutree
Move the existing rcu_barrier() implementation to rcutree.c,
consistent with the fact that the rcu_barrier() implementation is
tied quite tightly to the RCU implementation.

This opens the way to simplify and fix rcutree.c's rcu_barrier()
implementation in a later patch.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
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: <12548908982563-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-10-07 08:11:20 +02:00
Paul E. McKenney
135c8aea55 rcu: Replace the rcu_barrier enum with pointer to call_rcu*() function
The rcu_barrier enum causes several problems:

  (1) you have to define the enum somewhere, and there is no
      convenient place,

  (2) the difference between TREE_RCU and TREE_PREEMPT_RCU causes
      problems when you need to map from rcu_barrier enum to struct
      rcu_state,

  (3) the switch statement are large, and

  (4) TINY_RCU really needs a different rcu_barrier() than do the
      treercu implementations.

So replace it with a functionally equivalent but cleaner function
pointer abstraction.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
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: <12541998232366-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-10-05 21:02:05 +02:00
Paul E. McKenney
162cc2794d rcu: Fix rcu_lock_map build failure on CONFIG_PROVE_LOCKING=y
Move the rcu_lock_map definition from rcutree.c to rcupdate.c so that
TINY_RCU can use lockdep.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-10-05 21:01:28 +02:00
Paul E. McKenney
9b2619aff0 rcu: Clean up code to address Ingo's checkpatch feedback
Move declarations and update storage classes to make checkpatch happy.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
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: <12537246441701-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-23 19:46:30 +02:00
Paul E. McKenney
a71fca58b7 rcu: Fix whitespace inconsistencies
Fix a number of whitespace ^Ierrors in the include/linux/rcu*
and the kernel/rcu* files.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
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
LKML-Reference: <20090918172819.GA24405@linux.vnet.ibm.com>
[ did more checkpatch fixlets ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-19 08:53:22 +02:00
Paul E. McKenney
16e3081191 rcu: Fix synchronize_rcu() for TREE_PREEMPT_RCU
The redirection of synchronize_sched() to synchronize_rcu() was
appropriate for TREE_RCU, but not for TREE_PREEMPT_RCU.

Fix this by creating an underlying synchronize_sched().  TREE_RCU
then redirects synchronize_rcu() to synchronize_sched(), while
TREE_PREEMPT_RCU has its own version of synchronize_rcu().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
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
LKML-Reference: <12528585111916-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-18 00:06:53 +02:00
Paul E. McKenney
1423cc033d rcu: Delay rcu_barrier() wait until beginning of next CPU-hotunplug operation.
Ingo Molnar reported this lockup:

 [  200.380003] Hangcheck: hangcheck value past margin!
 [  248.192003] INFO: task S99local:2974 blocked for more than 120 seconds.
 [  248.194532] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
 [  248.202330] S99local      D 0000000c  6256  2974   2687 0x00000000
 [  248.208929]  9c7ebe90 00000086 6b67ef8b 0000000c 9f25a610 81a69869 00000001 820b6990
 [  248.216123]  820b6990 820b6990 9c6e4c20 9c6e4eb4 82c78990 00000000 6b993559 0000000c
 [  248.220616]  9c7ebe90 8105f22a 9c6e4eb4 9c6e4c20 00000001 9c7ebe98 9c7ebeb4 81a65cb3
 [  248.229990] Call Trace:
 [  248.234049]  [<81a69869>] ? _spin_unlock_irqrestore+0x22/0x37
 [  248.239769]  [<8105f22a>] ? prepare_to_wait+0x48/0x4e
 [  248.244796]  [<81a65cb3>] rcu_barrier_cpu_hotplug+0xaa/0xc9
 [  248.250343]  [<8105f029>] ? autoremove_wake_function+0x0/0x38
 [  248.256063]  [<81062cf2>] notifier_call_chain+0x49/0x71
 [  248.261263]  [<81062da0>] raw_notifier_call_chain+0x11/0x13
 [  248.266809]  [<81a0b475>] _cpu_down+0x272/0x288
 [  248.271316]  [<81a0b4d5>] cpu_down+0x4a/0xa2
 [  248.275563]  [<81a0c48a>] store_online+0x2a/0x5e
 [  248.280156]  [<81a0c460>] ? store_online+0x0/0x5e
 [  248.284836]  [<814ddc35>] sysdev_store+0x20/0x28
 [  248.289429]  [<8112e403>] sysfs_write_file+0xb8/0xe3
 [  248.294369]  [<8112e34b>] ? sysfs_write_file+0x0/0xe3
 [  248.299396]  [<810e4c8f>] vfs_write+0x91/0x120
 [  248.303817]  [<810e4dc1>] sys_write+0x40/0x65
 [  248.308150]  [<81002d73>] sysenter_do_call+0x12/0x28

This change moves an RCU grace period delay off of the
critical path for CPU-hotunplug operations.

Since RCU callback migration is only performed on
CPU-hotunplug operations, and since the rcu_barrier() race is
provoked only by consecutive CPU-hotunplug operations, it is
not necessary to delay the end of a given CPU-hotunplug
operation.

We can instead choose to delay the beginning of the next
CPU-hotunplug operation.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Josh Triplett <josht@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
Cc: mathieu.desnoyers@polymtl.ca
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: hugh.dickins@tiscali.co.uk
Cc: benh@kernel.crashing.org
LKML-Reference: <20090819060614.GA14383@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-08-19 13:58:54 +02:00
Paul E. McKenney
2e59755808 rcu: Simplify RCU CPU-hotplug notification
Use the new cpu_notifier() API to simplify RCU's CPU-hotplug
notifiers, collapsing down to a single such notifier.

This makes it trivial to provide the notifier-ordering
guarantee that rcu_barrier() depends on.

Also remove redundant open_softirq() calls from Hierarchical
RCU notifier.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: josht@linux.vnet.ibm.com
Cc: akpm@linux-foundation.org
Cc: mathieu.desnoyers@polymtl.ca
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: hugh.dickins@tiscali.co.uk
Cc: benh@kernel.crashing.org
LKML-Reference: <12503552312510-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-08-15 19:02:08 +02:00
Paul E. McKenney
03b042bf1d rcu: Add synchronize_sched_expedited() primitive
This adds the synchronize_sched_expedited() primitive that
implements the "big hammer" expedited RCU grace periods.

This primitive is placed in kernel/sched.c rather than
kernel/rcupdate.c due to its need to interact closely with the
migration_thread() kthread.

The idea is to wake up this kthread with req->task set to NULL,
in response to which the kthread reports the quiescent state
resulting from the kthread having been scheduled.

Because this patch needs to fallback to the slow versions of
the primitives in response to some races with CPU onlining and
offlining, a new synchronize_rcu_bh() primitive is added as
well.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: akpm@linux-foundation.org
Cc: torvalds@linux-foundation.org
Cc: davem@davemloft.net
Cc: dada1@cosmosbay.com
Cc: zbr@ioremap.net
Cc: jeff.chua.linux@gmail.com
Cc: paulus@samba.org
Cc: laijs@cn.fujitsu.com
Cc: jengelh@medozas.de
Cc: r000n@r000n.net
Cc: benh@kernel.crashing.org
Cc: mathieu.desnoyers@polymtl.ca
LKML-Reference: <12459460982947-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-07-03 10:02:28 +02:00
David Howells
5b1d07ed0e RCU: Don't try and predeclare inline funcs as it upsets some versions of gcc
Don't try and predeclare inline funcs like this:

	static inline void wait_migrated_callbacks(void)
	...
	static void _rcu_barrier(enum rcu_barrier type)
	{
		...
		wait_migrated_callbacks();
	}
	...
	static inline void wait_migrated_callbacks(void)
	{
		wait_event(rcu_migrate_wq, !atomic_read(&rcu_migrate_type_count));
	}

as it upsets some versions of gcc under some circumstances:

	kernel/rcupdate.c: In function `_rcu_barrier':
	kernel/rcupdate.c:125: sorry, unimplemented: inlining failed in call to 'wait_migrated_callbacks': function body not available
	kernel/rcupdate.c:152: sorry, unimplemented: called from here

This can be dealt with by simply putting the static variables (rcu_migrate_*)
at the top, and moving the implementation of the function up so that it
replaces its forward declaration.

Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-04-15 13:55:14 -07:00
Lai Jiangshan
f69b17d7e7 rcu: rcu_barrier VS cpu_hotplug: Ensure callbacks in dead cpu are migrated to online cpu
cpu hotplug may happen asynchronously, some rcu callbacks are maybe
still on dead cpu, rcu_barrier() also needs to wait for these rcu
callbacks to complete, so we must ensure callbacks in dead cpu are
migrated to online cpu.

Paul E. McKenney's review:

  Good stuff, Lai!!!  Simpler than any of the approaches that I was
  considering, and, better yet, independent of the underlying RCU
  implementation!!!

  I was initially worried that wake_up() might wake only one of two
  possible wait_event()s, namely rcu_barrier() and the CPU_POST_DEAD code,
  but the fact that wait_event() clears WQ_FLAG_EXCLUSIVE avoids that issue.
  I was also worried about the fact that different RCU implementations have
  different mappings of call_rcu(), call_rcu_bh(), and call_rcu_sched(), but
  this is OK as well because we just get an extra (harmless) callback in the
  case that they map together (for example, Classic RCU has call_rcu_sched()
  mapping to call_rcu()).

  Overlap of CPU-hotplug operations is prevented by cpu_add_remove_lock,
  and any stray callbacks that arrive (for example, from irq handlers
  running on the dying CPU) either are ahead of the CPU_DYING callbacks on
  the one hand (and thus accounted for), or happened after the rcu_barrier()
  started on the other (and thus don't need to be accounted for).

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <49C36476.1010400@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-31 00:09:37 +02:00
Paul E. McKenney
a682604838 rcu: Teach RCU that idle task is not quiscent state at boot
This patch fixes a bug located by Vegard Nossum with the aid of
kmemcheck, updated based on review comments from Nick Piggin,
Ingo Molnar, and Andrew Morton.  And cleans up the variable-name
and function-name language.  ;-)

The boot CPU runs in the context of its idle thread during boot-up.
During this time, idle_cpu(0) will always return nonzero, which will
fool Classic and Hierarchical RCU into deciding that a large chunk of
the boot-up sequence is a big long quiescent state.  This in turn causes
RCU to prematurely end grace periods during this time.

This patch changes the rcutree.c and rcuclassic.c rcu_check_callbacks()
function to ignore the idle task as a quiescent state until the
system has started up the scheduler in rest_init(), introducing a
new non-API function rcu_idle_now_means_idle() to inform RCU of this
transition.  RCU maintains an internal rcu_idle_cpu_truthful variable
to track this state, which is then used by rcu_check_callback() to
determine if it should believe idle_cpu().

Because this patch has the effect of disallowing RCU grace periods
during long stretches of the boot-up sequence, this patch also introduces
Josh Triplett's UP-only optimization that makes synchronize_rcu() be a
no-op if num_online_cpus() returns 1.  This allows boot-time code that
calls synchronize_rcu() to proceed normally.  Note, however, that RCU
callbacks registered by call_rcu() will likely queue up until later in
the boot sequence.  Although rcuclassic and rcutree can also use this
same optimization after boot completes, rcupreempt must restrict its
use of this optimization to the portion of the boot sequence before the
scheduler starts up, given that an rcupreempt RCU read-side critical
section may be preeempted.

In addition, this patch takes Nick Piggin's suggestion to make the
system_state global variable be __read_mostly.

Changes since v4:

o	Changes the name of the introduced function and variable to
	be less emotional.  ;-)

Changes since v3:

o	WARN_ON(nr_context_switches() > 0) to verify that RCU
	switches out of boot-time mode before the first context
	switch, as suggested by Nick Piggin.

Changes since v2:

o	Created rcu_blocking_is_gp() internal-to-RCU API that
	determines whether a call to synchronize_rcu() is itself
	a grace period.

o	The definition of rcu_blocking_is_gp() for rcuclassic and
	rcutree checks to see if but a single CPU is online.

o	The definition of rcu_blocking_is_gp() for rcupreempt
	checks to see both if but a single CPU is online and if
	the system is still in early boot.

	This allows rcupreempt to again work correctly if running
	on a single CPU after booting is complete.

o	Added check to rcupreempt's synchronize_sched() for there
	being but one online CPU.

Tested all three variants both SMP and !SMP, booted fine, passed a short
rcutorture test on both x86 and Power.

Located-by: Vegard Nossum <vegard.nossum@gmail.com>
Tested-by: Vegard Nossum <vegard.nossum@gmail.com>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-02-26 04:08:14 +01:00
Paul E. McKenney
ea7d3fef42 rcu: eliminate synchronize_rcu_xxx macro
Impact: cleanup

Expand macro into two files.

The synchronize_rcu_xxx macro is quite ugly and it's only used by two
callers, so expand it instead.  This makes this code easier to change.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-05 10:18:08 +01:00
Lai Jiangshan
5f86515158 rcupdate: fix bug of rcu_barrier*()
current rcu_barrier_bh() is like this:

void rcu_barrier_bh(void)
{
	BUG_ON(in_interrupt());
	/* Take cpucontrol mutex to protect against CPU hotplug */
	mutex_lock(&rcu_barrier_mutex);
	init_completion(&rcu_barrier_completion);
	atomic_set(&rcu_barrier_cpu_count, 0);
	/*
	 * The queueing of callbacks in all CPUs must be atomic with
	 * respect to RCU, otherwise one CPU may queue a callback,
	 * wait for a grace period, decrement barrier count and call
	 * complete(), while other CPUs have not yet queued anything.
	 * So, we need to make sure that grace periods cannot complete
	 * until all the callbacks are queued.
	 */
	rcu_read_lock();
	on_each_cpu(rcu_barrier_func, (void *)RCU_BARRIER_BH, 1);
	rcu_read_unlock();
	wait_for_completion(&rcu_barrier_completion);
	mutex_unlock(&rcu_barrier_mutex);
}

The inconsistency of the code and the comments show a bug here.
rcu_read_lock() cannot make sure that "grace periods for RCU_BH
cannot complete until all the callbacks are queued".
it only make sure that race periods for RCU cannot complete
until all the callbacks are queued.

so we must use rcu_read_lock_bh() for rcu_barrier_bh().
like this:

void rcu_barrier_bh(void)
{
	......
	rcu_read_lock_bh();
	on_each_cpu(rcu_barrier_func, (void *)RCU_BARRIER_BH, 1);
	rcu_read_unlock_bh();
	......
}

and also rcu_barrier() rcu_barrier_sched() are implemented like this.
it will bring a lot of duplicate code. My patch uses another way to
fix this bug, please see the comment of my patch.
Thank Paul E. McKenney for he rewrote the comment.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-21 15:59:53 +02:00
Randy Dunlap
01dcb0443e rcu: fix synchronize_rcu() so that kernel-doc works
Fix RCU's synchronize_rcu() so that it looks like a C function, enabling
it to be recognized as a function with kernel-doc annotation.

Warning(linux-2.6.26-git11//kernel/rcupdate.c:81): No description found for parameter 'synchronize_rcu'
Warning(linux-2.6.26-git11//kernel/rcupdate.c:81): No description found for parameter 'call_rcu'

[akpm@linux-foundation.org: fix comment]
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-08-21 09:31:44 +02:00
Linus Torvalds
59190f4213 Merge branch 'generic-ipi-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'generic-ipi-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (22 commits)
  generic-ipi: more merge fallout
  generic-ipi: merge fix
  x86, visws: use mach-default/entry_arch.h
  x86, visws: fix generic-ipi build
  generic-ipi: fixlet
  generic-ipi: fix s390 build bug
  generic-ipi: fix linux-next tree build failure
  fix: "smp_call_function: get rid of the unused nonatomic/retry argument"
  fix: "smp_call_function: get rid of the unused nonatomic/retry argument"
  fix "smp_call_function: get rid of the unused nonatomic/retry argument"
  on_each_cpu(): kill unused 'retry' parameter
  smp_call_function: get rid of the unused nonatomic/retry argument
  sh: convert to generic helpers for IPI function calls
  parisc: convert to generic helpers for IPI function calls
  mips: convert to generic helpers for IPI function calls
  m32r: convert to generic helpers for IPI function calls
  arm: convert to generic helpers for IPI function calls
  alpha: convert to generic helpers for IPI function calls
  ia64: convert to generic helpers for IPI function calls
  powerpc: convert to generic helpers for IPI function calls
  ...

Fix trivial conflicts due to rcu updates in kernel/rcupdate.c manually
2008-07-15 14:12:03 -07:00
Jens Axboe
15c8b6c1aa on_each_cpu(): kill unused 'retry' parameter
It's not even passed on to smp_call_function() anymore, since that
was removed. So kill it.

Acked-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-06-26 11:24:38 +02:00
Paul E. McKenney
70f12f848d rcu: add rcu_barrier_sched() and rcu_barrier_bh()
Add rcu_barrier_sched() and rcu_barrier_bh().  With these in place,
rcutorture no longer gives the occasional oops when repeatedly starting
and stopping torturing rcu_bh.  Also adds the API needed to flush out
pre-existing call_rcu_sched() callbacks.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-19 10:01:36 +02:00
Paul E. McKenney
4446a36ff8 rcu: add call_rcu_sched()
Fourth cut of patch to provide the call_rcu_sched().  This is again to
synchronize_sched() as call_rcu() is to synchronize_rcu().

Should be fine for experimental and -rt use, but not ready for inclusion.
With some luck, I will be able to tell Andrew to come out of hiding on
the next round.

Passes multi-day rcutorture sessions with concurrent CPU hotplugging.

Fixes since the first version include a bug that could result in
indefinite blocking (spotted by Gautham Shenoy), better resiliency
against CPU-hotplug operations, and other minor fixes.

Fixes since the second version include reworking grace-period detection
to avoid deadlocks that could happen when running concurrently with
CPU hotplug, adding Mathieu's fix to avoid the softlockup messages,
as well as Mathieu's fix to allow use earlier in boot.

Fixes since the third version include a wrong-CPU bug spotted by
Andrew, getting rid of the obsolete synchronize_kernel API that somehow
snuck back in, merging spin_unlock() and local_irq_restore() in a
few places, commenting the code that checks for quiescent states based
on interrupting from user-mode execution or the idle loop, removing
some inline attributes, and some code-style changes.

Known/suspected shortcomings:

o	I still do not entirely trust the sleep/wakeup logic.  Next step
	will be to use a private snapshot of the CPU online mask in
	rcu_sched_grace_period() -- if the CPU wasn't there at the start
	of the grace period, we don't need to hear from it.  And the
	bit about accounting for changes in online CPUs inside of
	rcu_sched_grace_period() is ugly anyway.

o	It might be good for rcu_sched_grace_period() to invoke
	resched_cpu() when a given CPU wasn't responding quickly,
	but resched_cpu() is declared static...

This patch also fixes a long-standing bug in the earlier preemptable-RCU
implementation of synchronize_rcu() that could result in loss of
concurrent external changes to a task's CPU affinity mask.  I still cannot
remember who reported this...

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-19 10:01:36 +02:00
Paul E. McKenney
fbf6bfca76 rcupdate: fix comment
This comment caused some consternation during fastcall removal.  Make it
truthful.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-13 16:21:18 -08:00
Paul E. McKenney
e0ecfa7917 Preempt-RCU: fix rcu_barrier for preemptive environment.
Fix rcu_barrier() to work properly in preemptive kernel environment.
Also, the ordering of callback must be preserved while moving
callbacks to another CPU during CPU hotplug.

Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-01-25 21:08:24 +01:00
Paul E. McKenney
01c1c660f4 Preempt-RCU: reorganize RCU code into rcuclassic.c and rcupdate.c
This patch re-organizes the RCU code to enable multiple implementations
of RCU. Users of RCU continues to include rcupdate.h and the
RCU interfaces remain the same. This is in preparation for
subsequently merging the preemptible RCU implementation.

Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-01-25 21:08:24 +01:00
Dipankar Sarma
c2d727aa2f Preempt-RCU: Use softirq instead of tasklets for
This patch makes RCU use softirq instead of tasklets.

It also adds a memory barrier after raising the softirq
inorder to ensure that the cpu sees the most recently updated
value of rcu->cur while processing callbacks.
The discussion of the related theoretical race pointed out
by James Huang can be found here --> http://lkml.org/lkml/2007/11/20/603

Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Reviewed-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-01-25 21:08:23 +01:00
Randy Dunlap
00e10776ff rcu: fix section mismatch
rcu_online_cpu() should be __cpuinit instead of __devinit.

WARNING: vmlinux.o(.text+0x4b6d5): Section mismatch: reference to .init.text: (between 'rcu_cpu_notify' and 'wakeme_after_rcu')

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-01-22 09:17:48 -08:00
Jesper Juhl
a9022e9cb9 Clean up duplicate includes in kernel/
This patch cleans up duplicate includes in
	kernel/

Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Satyam Sharma <ssatyam@cse.iitk.ac.in>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-17 08:42:48 -07:00
Peter Zijlstra
851a67b825 lockdep: annotate rcu_read_{,un}lock{,_bh}
lockdep annotate rcu_read_{,un}lock{,_bh} in order to catch imbalanced
usage.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2007-10-11 22:11:12 +02:00
Rafael J. Wysocki
8bb7844286 Add suspend-related notifications for CPU hotplug
Since nonboot CPUs are now disabled after tasks and devices have been
frozen and the CPU hotplug infrastructure is used for this purpose, we need
special CPU hotplug notifications that will help the CPU-hotplug-aware
subsystems distinguish normal CPU hotplug events from CPU hotplug events
related to a system-wide suspend or resume operation in progress.  This
patch introduces such notifications and causes them to be used during
suspend and resume transitions.  It also changes all of the
CPU-hotplug-aware subsystems to take these notifications into consideration
(for now they are handled in the same way as the corresponding "normal"
ones).

[oleg@tv-sign.ru: cleanups]
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-09 12:30:56 -07:00
Eric Dumazet
1c69d921ed [PATCH] rcu: add a prefetch() in rcu_do_batch()
On some workloads, (for example when lot of close() syscalls are done), RCU
qlen can be quite large, and RCU heads are no longer in cpu cache when
rcu_do_batch() is called.

This patch adds a prefetch() in rcu_do_batch() to give CPU a hint to bring
back cache lines containing 'struct rcu_head's.

Most list manipulations macros include prefetch(), but not open coded ones
(at least with current C compilers :) )

I got a nice speedup on a trivial benchmark (3.48 us per iteration instead
of 3.95 us on a 1.6 GHz Pentium-M)

while (1) { pipe(p); close(fd[0]); close(fd[1]);}

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-07 08:39:40 -08:00
Oleg Nesterov
20e9751bd9 [PATCH] rcu: simplify/improve batch tuning
Kill a hard-to-calculate 'rsinterval' boot parameter and per-cpu
rcu_data.last_rs_qlen.  Instead, it adds adds a flag rcu_ctrlblk.signaled,
which records the fact that one of CPUs has sent a resched IPI since the
last rcu_start_batch().

Roughly speaking, we need two rcu_start_batch()s in order to move callbacks
from ->nxtlist to ->donelist.  This means that when ->qlen exceeds qhimark
and continues to grow, we should send a resched IPI, and then do it again
after we gone through a quiescent state.

On the other hand, if it was already sent, we don't need to do it again
when another CPU detects overflow of the queue.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-04 07:55:31 -07:00
Oleg Nesterov
dd9daa221e [PATCH] rcu_do_batch: make ->qlen decrement irq safe
rcu_do_batch() decrements rdp->qlen with irqs enabled.  This is not good,
it can also be modified by call_rcu() from interrupt.

Decrement ->qlen once with irqs disabled, after a main loop.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-09-13 07:32:14 -07:00
Chandra Seetharaman
8c78f3075d [PATCH] cpu hotplug: replace __devinit* with __cpuinit* for cpu notifications
Few of the callback functions and notifier blocks that are associated with cpu
notifications incorrectly have __devinit and __devinitdata.  They should be
__cpuinit and __cpuinitdata instead.

It makes no functional difference but wastes text area when CONFIG_HOTPLUG is
enabled and CONFIG_HOTPLUG_CPU is not.

This patch fixes all those instances.

Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-07-31 13:28:39 -07:00
Ingo Molnar
e4d9191885 [PATCH] lockdep: locking init debugging improvement
Locking init improvement:

 - introduce and use __SPIN_LOCK_UNLOCKED for array initializations,
   to pass in the name string of locks, used by debugging

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-07-03 15:27:02 -07:00
Chandra Seetharaman
054cc8a2d8 [PATCH] cpu hotplug: revert initdata patch submitted for 2.6.17
This patch reverts notifier_block changes made in 2.6.17

Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-27 17:32:41 -07:00
Chandra Seetharaman
9c7b216d23 [PATCH] cpu hotplug: revert init patch submitted for 2.6.17
In 2.6.17, there was a problem with cpu_notifiers and XFS.  I provided a
band-aid solution to solve that problem.  In the process, i undid all the
changes you both were making to ensure that these notifiers were available
only at init time (unless CONFIG_HOTPLUG_CPU is defined).

We deferred the real fix to 2.6.18.  Here is a set of patches that fixes the
XFS problem cleanly and makes the cpu notifiers available only at init time
(unless CONFIG_HOTPLUG_CPU is defined).

If CONFIG_HOTPLUG_CPU is defined then cpu notifiers are available at run
time.

This patch reverts the notifier_call changes made in 2.6.17

Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-27 17:32:40 -07:00
Paul E. McKenney
c32e066057 [PATCH] rcutorture: add call_rcu_bh() operations
Add operations for the call_rcu_bh() variant of RCU.  Also add an
rcu_batches_completed_bh() function, which is needed by rcutorture.

Signed-off-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-27 17:32:40 -07:00
Paul E. McKenney
d83015b8f6 [PATCH] Make RCU API inaccessible to non-GPL Linux kernel modules
Remove synchronize_kernel() (deprecated 2-APR-2005 in
http://lkml.org/lkml/2005/4/3/11) and makes the RCU API inaccessible to
non-GPL Linux kernel modules (as was announced more than one year ago in
http://lkml.org/lkml/2005/4/3/8).  Tested on x86 and ppc64.

Signed-off-by: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 07:43:07 -07:00
Heiko Carstens
986733e01d [PATCH] RCU: introduce rcu_needs_cpu() interface
With "Paul E. McKenney" <paulmck@us.ibm.com>

Introduce rcu_needs_cpu() interface.  This can be used to tell if there
will be a new rcu batch on a cpu soon by looking at the curlist pointer.
This can be used to avoid to enter a tickless idle state where the cpu
would miss that a new batch is ready when rcu_start_batch would be called
on a different cpu.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-05-15 11:20:55 -07:00
Chandra Seetharaman
83d722f7e1 [PATCH] Remove __devinit and __cpuinit from notifier_call definitions
Few of the notifier_chain_register() callers use __init in the definition
of notifier_call.  It is incorrect as the function definition should be
available after the initializations (they do not unregister them during
initializations).

This patch fixes all such usages to _not_ have the notifier_call __init
section.

Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-04-26 08:30:03 -07:00
Chandra Seetharaman
649bbaa484 [PATCH] Remove __devinitdata from notifier block definitions
Few of the notifier_chain_register() callers use __devinitdata in the
definition of notifier_block data structure.  It is incorrect as the
data structure should be available after the initializations (they do
not unregister them during initializations).

This was leading to an oops when notifier_chain_register() call is
invoked for those callback chains after initialization.

This patch fixes all such usages to _not_ have the notifier_block data
structure in the init data section.

Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-04-26 08:27:50 -07:00
Oleg Nesterov
caa9ee771d [PATCH] rcu_process_callbacks: don't cli() while testing ->nxtlist
__rcu_process_callbacks() disables interrupts to protect itself from
call_rcu() which adds new entries to ->nxtlist.

However we can check "->nxtlist != NULL" with interrupts enabled, we can't
get "false positives" because call_rcu() can only change this condition
from 0 to 1.

Tested with rcutorture.ko.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Dipankar Sarma <dipankar@in.ibm.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-24 07:33:20 -08:00
Adrian Bunk
2178426d26 [PATCH] kernel/rcupdate.c: make two structs static
This patch makes two needlessly global structs static.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-23 07:38:17 -08:00
Ingo Molnar
9331b3157c [PATCH] convert kernel/rcupdate.c:rcu_barrier_sema to mutex
Convert kernel/rcupdate's rcu_barrier_sema to mutex.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-23 07:38:10 -08:00
Greg Kroah-Hartman
01ca70dca5 [PATCH] add EXPORT_SYMBOL_GPL_FUTURE() to RCU subsystem
As the RCU symbols are going to be changed to GPL in the near future,
lets warn users that this is going to happen.

Cc: Paul McKenney <paulmck@us.ibm.com>
Acked-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2006-03-20 13:42:58 -08:00
Dipankar Sarma
21a1ea9eb4 [PATCH] rcu batch tuning
This patch adds new tunables for RCU queue and finished batches.  There are
two types of controls - number of completed RCU updates invoked in a batch
(blimit) and monitoring for high rate of incoming RCUs on a cpu (qhimark,
qlowmark).

By default, the per-cpu batch limit is set to a small value.  If the input
RCU rate exceeds the high watermark, we do two things - force quiescent
state on all cpus and set the batch limit of the CPU to INTMAX.  Setting
batch limit to INTMAX forces all finished RCUs to be processed in one shot.
 If we have more than INTMAX RCUs queued up, then we have bigger problems
anyway.  Once the incoming queued RCUs fall below the low watermark, the
batch limit is set to the default.

Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-08 14:14:01 -08:00
Oleg Nesterov
a9c828155a [PATCH] rcu: fix hotplug-cpu ->donelist leak
Pointed out by Srivatsa Vaddagiri <vatsa@in.ibm.com>.

rcu_do_batch() stops after processing maxbatch callbacks
on ->donelist leaving rcu_tasklet in TASKLET_STATE_SCHED
state.

If CPU_DEAD event happens remaining ->donelist entries are
lost, rcu_offline_cpu() kills this tasklet.

With this patch ->donelist migrates along with ->curlist
and ->nxtlist to the current cpu.

Compile tested.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-10 08:49:47 -08:00
Oleg Nesterov
69a0b31579 [PATCH] rcu: join rcu_ctrlblk and rcu_state
This patch moves rcu_state into the rcu_ctrlblk. I think there
are no reasons why we should have 2 different variables to control
rcu state. Every user of rcu_state has also "rcu_ctrlblk *rcp" in
the parameter list.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-10 08:42:50 -08:00
Oleg Nesterov
dbc1651f0c [PATCH] rcu: don't set ->next_pending in rcu_start_batch()
I think it is better to set ->next_pending in the caller, when
it is needed. This saves one parameter, and this coincides with
cpu_quiet() beahaviour, which sets ->completed = ->cur itself.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-09 17:01:39 -08:00
Oleg Nesterov
677517771b [PATCH] rcu: uninline __rcu_pending()
__rcu_pending() is rather fat and called twice from rcu_pending().

rcu_pending() has multiple callers, and not that small too.

This patch uninlines both of them.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-09 09:35:44 -08:00
Nick Piggin
095975da26 [PATCH] rcu file: use atomic primitives
Use atomic_inc_not_zero for rcu files instead of special case rcuref.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-08 20:13:48 -08:00
Ingo Molnar
e56d090310 [PATCH] RCU signal handling
RCU tasklist_lock and RCU signal handling: send signals RCU-read-locked
instead of tasklist_lock read-locked.  This is a scalability improvement on
SMP and a preemption-latency improvement under PREEMPT_RCU.

Signed-off-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: William Irwin <wli@holomorphy.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-08 20:13:40 -08:00