linux-toradex.git/include/linux/cpu.h, branch v2.6.34-rc3

powerpc/pseries: Serialize cpu hotplug operations during deactivate Vs deallocate

2009-12-09T06:09:36+00:00

Currently the cpu-allocation/deallocation process comprises of two steps:
- Set the indicators and to update the device tree with DLPAR node
  information.

- Online/offline the allocated/deallocated CPU.

This is achieved by writing to the sysfs tunables "probe" during allocation
and "release" during deallocation.

At the sametime, the userspace can independently online/offline the CPUs of
the system using the sysfs tunable "online".

It is quite possible that when a userspace tool offlines a CPU
for the purpose of deallocation and is in the process of updating the device
tree, some other userspace tool could bring the CPU back online by writing to
the "online" sysfs tunable thereby causing the deallocate process to fail.

The solution to this is to serialize writes to the "probe/release" sysfs
tunable with the writes to the "online" sysfs tunable.

This patch employs a mutex to provide this serialization, which is a no-op on
all architectures except PPC_PSERIES

Signed-off-by: Gautham R Shenoy 
Acked-by: Vaidyanathan Srinivasan 
Signed-off-by: Benjamin Herrenschmidt

sysfs/cpu: Add probe/release files

2009-12-09T06:09:33+00:00

Version 3 of this patch is updated with documentation added to
Documentation/ABI.  There are no changes to any of the C code from v2
of the patch.

In order to support kernel DLPAR of CPU resources we need to provide an
interface to add (probe) and remove (release) the resource from the system.
This patch Creates new generic probe and release sysfs files to facilitate
cpu probe/release.  The probe/release interface provides for allowing each
arch to supply their own routines for implementing the backend of adding
and removing cpus to/from the system.

This also creates the powerpc specific stubs to handle the arch callouts
from writes to the sysfs files.

The creation and use of these files is regulated by the
CONFIG_ARCH_CPU_PROBE_RELEASE option so that only architectures that need the
capability will have the files created.

Signed-off-by: Nathan Fontenot 
Signed-off-by: Benjamin Herrenschmidt

cpu hotplug: Introduce cpu_notifier() to handle !HOTPLUG_CPU case

2009-08-15T17:02:07+00:00

This patch introduces a new cpu_notifier() API that is similar
to hotcpu_notifier(), but which also notifies of CPUs coming
online during boot in the !HOTPLUG_CPU case.

Reported-by: Ingo Molnar 
Reported-by: Hugh Dickins 
Tested-by: Hugh Dickins 
Signed-off-by: Paul E. McKenney 
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: benh@kernel.crashing.org
LKML-Reference: <12503552312611-git-send-email->
Signed-off-by: Ingo Molnar

mm/init: cpu_hotplug_init() must be initialized before SLAB

2009-06-23T04:18:12+00:00

SLAB uses get/put_online_cpus() which use a mutex which is itself only
initialized when cpu_hotplug_init() is called.  Currently we hang suring
boot in SLAB due to doing that too late.

Reported by James Bottomley and Sachin Sant (and possibly others).
Debugged by Benjamin Herrenschmidt.

This just removes the dynamic initialization of the data structures, and
replaces it with a static one, avoiding this dependency entirely, and
removing one unnecessary special initcall.

Tested-by: Sachin Sant 
Tested-by: James Bottomley 
Tested-by: Benjamin Herrenschmidt 
Signed-off-by: Linus Torvalds

cpu hotplug: remove unused cpuhotplug_mutex_lock()

2009-04-03T02:05:00+00:00

cpuhotplug_mutex_lock() is not used, remove it.

Signed-off-by: Lai Jiangshan 
Cc: Ingo Molnar 
Cc: Rusty Russell 
Acked-by: Gautham R Shenoy 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kernel/cpu.c: create a CPU_STARTING cpu_chain notifier

2008-09-08T17:25:24+00:00

Right now, there is no notifier that is called on a new cpu, before the new
cpu begins processing interrupts/softirqs.
Various kernel function would need that notification, e.g. kvm works around
by calling smp_call_function_single(), rcu polls cpu_online_map.

The patch adds a CPU_STARTING notification. It also adds a helper function
that sends the message to all cpu_chain handlers.

Tested on x86-64.
All other archs are untested. Especially on sparc, I'm not sure if I got
it right.

Signed-off-by: Manfred Spraul 
Signed-off-by: Ingo Molnar

workqueues: make get_online_cpus() useable for work->func()

2008-07-25T17:53:40+00:00

workqueue_cpu_callback(CPU_DEAD) flushes cwq->thread under
cpu_maps_update_begin().  This means that the multithreaded workqueues
can't use get_online_cpus() due to the possible deadlock, very bad and
very old problem.

Introduce the new state, CPU_POST_DEAD, which is called after
cpu_hotplug_done() but before cpu_maps_update_done().

Change workqueue_cpu_callback() to use CPU_POST_DEAD instead of CPU_DEAD.
This means that create/destroy functions can't rely on get_online_cpus()
any longer and should take cpu_add_remove_lock instead.

[akpm@linux-foundation.org: fix CONFIG_SMP=n]
Signed-off-by: Oleg Nesterov 
Acked-by: Gautham R Shenoy 
Cc: Heiko Carstens 
Cc: Max Krasnyansky 
Cc: Paul Jackson 
Cc: Paul Menage 
Cc: Peter Zijlstra 
Cc: Vegard Nossum 
Cc: Martin Schwidefsky 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

cpu: fix section mismatch warnings in hotcpu_register

2008-04-29T15:05:59+00:00

Fix following warnings:
WARNING: vmlinux.o(.data+0x5020): Section mismatch in reference from the variable cpu_vsyscall_notifier_nb.12876 to the function .cpuinit.text:cpu_vsyscall_notifier()
WARNING: vmlinux.o(.data+0x9ce0): Section mismatch in reference from the variable profile_cpu_callback_nb.17654 to the function .devinit.text:profile_cpu_callback()
WARNING: vmlinux.o(.data+0xd380): Section mismatch in reference from the variable workqueue_cpu_callback_nb.15004 to the function .devinit.text:workqueue_cpu_callback()
WARNING: vmlinux.o(.data+0x11d00): Section mismatch in reference from the variable relay_hotcpu_callback_nb.19626 to the function .cpuinit.text:relay_hotcpu_callback()
WARNING: vmlinux.o(.data+0x12970): Section mismatch in reference from the variable cpu_callback_nb.24694 to the function .devinit.text:cpu_callback()
WARNING: vmlinux.o(.data+0x3fee0): Section mismatch in reference from the variable percpu_counter_hotcpu_callback_nb.10903 to the function .cpuinit.text:percpu_counter_hotcpu_callback()
WARNING: vmlinux.o(.data+0x74ce0): Section mismatch in reference from the variable topology_cpu_callback_nb.12506 to the function .cpuinit.text:topology_cpu_callback()

Functions used as argument are by definition only used in HOTPLUG_CPU
situations so thay are annotated __cpuinit.  Annotate the static variable used
by hotcpu_register with __cpuinitdata to match this definition.

Signed-off-by: Sam Ravnborg 
Cc: Gautham R Shenoy 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

include: Remove unnecessary inclusions of asm/semaphore.h

2008-04-19T02:16:54+00:00

None of these files use any of the functionality promised by
asm/semaphore.h.  It's possible that they (or some user of them) rely
on it dragging in some unrelated header file, but I can't build all
these files, so we'll have to fix any build failures as they come up.

Signed-off-by: Matthew Wilcox

cpu-hotplug: fix build on !CONFIG_SMP

2008-01-25T20:08:02+00:00

fix build on !CONFIG_SMP.

Signed-off-by: Ingo Molnar