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The CPU hotplug locking was quite messy, with a recursive lock to
handle the fact that both the actual up/down sequence wanted to
protect itself from being re-entered, but the callbacks that it
called also tended to want to protect themselves from CPU events.
This splits the lock into two (one to serialize the whole hotplug
sequence, the other to protect against the CPU present bitmaps
changing). The latter still allows recursive usage because some
subsystems (ondemand policy for cpufreq at least) had already gotten
too used to the lax locking, but the locking mistakes are hopefully
now less fundamental, and we now warn about recursive lock usage
when we see it, in the hope that it can be fixed.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Always use do {} while (0). Failing to do so can cause subtle compile
failures or bugs.
Cc: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Define new macros register_hotcpu_notifier() and unregister_hotcpu_notifier()
that redefines register_cpu_notifier() and unregister_cpu_notifier() for use
only when HOTPLUG_CPU is defined.
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>
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CPUs come online only at init time (unless CONFIG_HOTPLUG_CPU is defined).
So, cpu_notifier functionality need to be available only at init time.
This patch makes register_cpu_notifier() available only at init time, unless
CONFIG_HOTPLUG_CPU is defined.
This patch exports register_cpu_notifier() and unregister_cpu_notifier() only
if CONFIG_HOTPLUG_CPU is defined.
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>
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With Goto-san's patch, we can add new pgdat/node at runtime. I'm now
considering node-hot-add with cpu + memory on ACPI.
I found acpi container, which describes node, could evaluate cpu before
memory. This means cpu-hot-add occurs before memory hot add.
In most part, cpu-hot-add doesn't depend on node hot add. But register_cpu(),
which creates symbolic link from node to cpu, requires that node should be
onlined before register_cpu(). When a node is onlined, its pgdat should be
there.
This patch-set holds off creating symbolic link from node to cpu
until node is onlined.
This removes node arguments from register_cpu().
Now, register_cpu() requires 'struct node' as its argument. But the array of
struct node is now unified in driver/base/node.c now (By Goto's node hotplug
patch). We can get struct node in generic way. So, this argument is not
necessary now.
This patch also guarantees add cpu under node only when node is onlined. It
is necessary for node-hot-add vs. cpu-hot-add patch following this.
Moreover, register_cpu calculates cpu->node_id by cpu_to_node() without regard
to its 'struct node *root' argument. This patch removes it.
Also modify callers of register_cpu()/unregister_cpu, whose args are changed
by register-cpu-remove-node-struct patch.
[Brice.Goglin@ens-lyon.org: fix it]
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Brice Goglin <Brice.Goglin@ens-lyon.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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- Moved check for online cpu out of smp_prepare_cpu()
- Moved default declaration of smp_prepare_cpu() to kernel/cpu.c
- Removed lock_cpu_hotplug() from smp_prepare_cpu() to around it, since
its called from cpu_up() as well now.
- Removed clearing from cpu_present_map during cpu_offline as it breaks
using cpu_up() directly during a subsequent online operation.
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: "Li, Shaohua" <shaohua.li@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Doing (int < NR_CPUS) doesn't dtrt if it's negative..
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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There are some callers in cpufreq hotplug notify path that the lowest
function calls lock_cpu_hotplug(). The lock is already held during
cpu_up() and cpu_down() calls when the notify calls are broadcast to
registered clients.
Ideally if possible, we could disable_preempt() at the highest caller and
make sure we dont sleep in the path down in cpufreq->driver_target() calls
but the calls are so intertwined and cumbersome to cleanup.
Hence we consistently use lock_cpu_hotplug() and unlock_cpu_hotplug() in
all places.
- Removed export of cpucontrol semaphore and made it static.
- removed explicit uses of up/down with lock_cpu_hotplug()
so we can keep track of the the callers in same thread context and
just keep refcounts without calling a down() that causes a deadlock.
- Removed current_in_hotplug() uses
- Removed PF_HOTPLUG_CPU in sched.h introduced for the current_in_hotplug()
temporary workaround.
Tested with insmod of cpufreq_stat.ko, and logical online/offline
to make sure we dont have any hang situations.
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Cc: Zwane Mwaikambo <zwane@linuxpower.ca>
Cc: Shaohua Li <shaohua.li@intel.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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When calling target drivers to set frequency, we take cpucontrol lock.
When we modified the code to accomodate CPU hotplug, there was an attempt
to take a double lock of cpucontrol leading to a deadlock. Since the
current thread context is already holding the cpucontrol lock, we dont need
to make another attempt to acquire it.
Now we leave a trace in current->flags indicating current thread already is
under cpucontrol lock held, so we dont attempt to do this another time.
Thanks to Andrew Morton for the beating:-)
From: Brice Goglin <Brice.Goglin@ens-lyon.org>
Build fix
(akpm: this patch is still unpleasant. Ashok continues to look for a cleaner
solution, doesn't he? ;))
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Brice Goglin <Brice.Goglin@ens-lyon.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Some modules creating sysfs entries under /sys/devices/system/cpu/cpuX/
need to know the parent sysfs entry to make devices under them. This will
just return the sysfs entry for a given cpu.
sysfs entries showing under each cpu sysfs can be easily created if such
entries can be created by registering a sysfs driver for cpuclass. The
issue is when the entry is created the CPU may not be online, hence we
would need to defer the creation until the online notification comes.
Current users: cache entries for Intel CPU's and cpufreq subsystem.
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Dave Jones <davej@codemonkey.org.uk>
Cc: Zwane Mwaikambo <zwane@holomorphy.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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net/sunrpc/rpc_pipe.c
This patch is against 2.6.10, but still applies cleanly. It's just
s/driverfs/sysfs/ in these two files.
Signed-off-by: Rolf Eike Beer <eike-kernel@sf-tec.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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I really wish smp_prepare_cpu() would disappear eventually. In the interim
this is ideally a weak function, so we dont end up changing several places
to define this dummy in headers.
Today since the dummy declaration is done only in drivers/base/cpu.c but
the function is called in kernel/power/smp.c i get undefined reference in
my cpu hotplug code for x86_64 under development.
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Extend support for dynamic registration and unregistration of the cpu,
by implementing and exporting arch_register_cpu()/arch_unregister_cpu().
Also combine multiple implementation of topology_init() functions to
single topology_init() in case of ia64 architecture.
Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
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This means we won't get any warnings about unused
variables - they _are_ used in some configurations.
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This file provides ability for caller of register_cpu() to either create a
control file, or not. This can be handy if a particular platform decides
that certain CPU's are not removable. Hence would like to not create a
control file.
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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From: Nathan Lynch <nathanl@austin.ibm.com>
The hotcpu_notifier macro does not properly record the given priority in
the notifier block. This causes trouble only for callers which specify a
non-zero priority, of which there are none (yet).
Signed-off-by: Nathan Lynch <nathanl@austin.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Implement cpu_down(): uses stop_machine to freeze the machine, then
uses (arch-specific) __cpu_disable() and migrate_all_tasks().
Whole thing under CONFIG_HOTPLUG_CPU, so doesn't break archs which
don't define that.
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Note that without CONFIG_HOTPLUG_CPU, online cpus == possible cpus, so
substitutions are a noop.
- Changes show_stat to print out stats for every possible cpu, not
just online CPUs.
- Allocate mem in stat_open on possible, not online_cpus.
- Add conventient macros to cpu.h: especially cpu_is_offline() for
testing if a cpu is still online.
- Add a num_possible_cpus() similar to num_online_cpus(), and define
cpu_possible_mask for UP.
- Allow printk on down cpus once system is running.
- Mask cpumask with possible, not online cpus, for sys_getaffinity().
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From: Rusty Russell <rusty@rustcorp.com.au>
The cpucontrol mutex is not required when no cpus can go up and down.
Andrew wrote a wrapper for it to avoid #ifdefs, this expands that to only
be defined for CONFIG_HOTPLUG_CPU, and uses it everywhere.
The only downside is that the cpucontrol lock was overloaded by my recent
patch to net/core/flow.c to protect it from reentrance, so this
reintroduces the local flow_flush_sem. This code isn't speed critical, so
taking two locks when CONFIG_HOTPLUG_CPU=y is not really an issue.
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The code directly accessed the "cpucontrol" semaphore used
for CPU hotplug. That doesn't work all that well, since the
semaphore doesn't even exist on UP.
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Trivial patch: when these were introduced cpu.h didn't exist.
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This is an implementation of the in-kernel module loader extending
the try_inc_mod_count() primitive and making its use compulsory.
This has the benifit of simplicity, and similarity to the existing
scheme. To reduce the cost of the constant increments and
decrements, reference counters are lockless and per-cpu.
Eliminated (coming in following patches):
o Modversions
o Module parameters
o kallsyms
o EXPORT_SYMBOL_GPL and MODULE_LICENCE checks
o DEVICE_TABLE support.
New features:
o Typesafe symbol_get/symbol_put
o Single "insert this module" syscall interface allows trivial userspace.
o Raceless loading and unloading
You will need the trivial replacement module utilities from:
http://ozlabs.org/~rusty/module-init-tools-0.6.tar.gz
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From Matthew Dobson.
This final patch from Matthew cleans up a few leftovers which were noted
after the code had been reviewed and tested a bit in the -mm patchsets.
1) Update register_XXX and arch_register_XXX functions to return int
instead of void. Functions calling these functions should know if
they completed successfully to take appropriate further registration
action, or not bother.
2) Drop some pointless error checking in the arch_register_XXX
functions.
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From Matthew Dobson.
Update/Create core files for DriverFS Topology.
This patch creates the generic structures that are (will be) embedded in
the per-arch structures. Also creates calls to register these generic
structures (CPUs, MemBlks, & Nodes).
Note that without arch-specific structures in which to embed these
structures, and an arch-specific initialization routine, these
functions/structures remain unused.
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- Create struct cpu to generically describe cpus (it simply contains
a struct sys_device in it).
- Define an array of size NR_CPUS in arch/i386/kernel/cpu/common.c
and register each on bootup. This gives us something like:
# tree -d /sys/root/sys/
/sys/root/sys/
|-- cpu0
|-- pic0
`-- rtc0
and:
# tree -d /sys/bus/system/devices/
/sys/bus/system/devices/
|-- cpu0 -> ../../../root/sys/cpu0
- Define arch-specific CPU driver that's also registered on boot.
That gives us:
# tree -d /sys/bus/system/drivers/
/sys/bus/system/drivers/
|-- cpu
- Create a CPU device class that's registered very early. That
gives us all the CPUs in the system in one place:
# tree -d /sys/class/cpu/
/sys/class/cpu/
|-- devices
| `-- 0 -> ../../../root/sys/cpu0
`-- drivers
Other archs are encouraged to do the same.
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