user/sven/linux.git/include/linux/cpu.h, branch v3.2.78

CPU hotplug: provide a generic helper to disable/enable CPU hotplug

2013-06-19T01:16:59Z

commit 16e53dbf10a2d7e228709a7286310e629ede5e45 upstream. There are instances in the kernel where we would like to disable CPU hotplug (from sysfs) during some important operation. Today the freezer code depends on this and the code to do it was kinda tailor-made for that. Restructure the code and make it generic enough to be useful for other usecases too. Signed-off-by: Srivatsa S. Bhat Signed-off-by: Robin Holt Cc: H. Peter Anvin Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Russ Anderson Cc: Robin Holt Cc: Russell King Cc: Guan Xuetao Cc: Shawn Guo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Ben Hutchings

workqueue: perform cpu down operations from low priority cpu_notifier()

2012-08-02T13:37:51Z

commit 6575820221f7a4dd6eadecf7bf83cdd154335eda upstream. Currently, all workqueue cpu hotplug operations run off CPU_PRI_WORKQUEUE which is higher than normal notifiers. This is to ensure that workqueue is up and running while bringing up a CPU before other notifiers try to use workqueue on the CPU. Per-cpu workqueues are supposed to remain working and bound to the CPU for normal CPU_DOWN_PREPARE notifiers. This holds mostly true even with workqueue offlining running with higher priority because workqueue CPU_DOWN_PREPARE only creates a bound trustee thread which runs the per-cpu workqueue without concurrency management without explicitly detaching the existing workers. However, if the trustee needs to create new workers, it creates unbound workers which may wander off to other CPUs while CPU_DOWN_PREPARE notifiers are in progress. Furthermore, if the CPU down is cancelled, the per-CPU workqueue may end up with workers which aren't bound to the CPU. While reliably reproducible with a convoluted artificial test-case involving scheduling and flushing CPU burning work items from CPU down notifiers, this isn't very likely to happen in the wild, and, even when it happens, the effects are likely to be hidden by the following successful CPU down. Fix it by using different priorities for up and down notifiers - high priority for up operations and low priority for down operations. Workqueue cpu hotplug operations will soon go through further cleanup. Signed-off-by: Tejun Heo Acked-by: "Rafael J. Wysocki" Signed-off-by: Ben Hutchings

PM / Sleep: Remove unused symbol 'suspend_cpu_hotplug'

2011-11-04T21:28:09Z

Remove the suspend_cpu_hotplug declaration, which doesn't correspond to an existing variable. [rjw: Added the changelog.] Signed-off-by: Srivatsa S. Bhat Signed-off-by: Rafael J. Wysocki

notifiers: cpu: move cpu notifiers into cpu.h

2011-07-26T03:57:14Z

We presently define all kinds of notifiers in notifier.h. This is not necessary at all, since different subsystems use different notifiers, they are almost non-related with each other. This can also save much build time. Suppose I add a new netdevice event, really I don't have to recompile all the source, just network related. Without this patch, all the source will be recompiled. I move the notify events near to their subsystem notifier registers, so that they can be found more easily. This patch: It is not necessary to share the same notifier.h. Signed-off-by: WANG Cong Cc: David Miller Cc: "Rafael J. Wysocki" Cc: Greg KH Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

driver core: prune docs about device_interface

2010-11-11T00:57:11Z

drivers/base/intf.c was removed before the beginning of (git) time but its Documentation stuck around. Remove it. Signed-off-by: Brandon Philips Signed-off-by: Greg Kroah-Hartman

workqueue: reimplement CPU hotplugging support using trustee

2010-06-29T08:07:12Z

Reimplement CPU hotplugging support using trustee thread. On CPU down, a trustee thread is created and each step of CPU down is executed by the trustee and workqueue_cpu_callback() simply drives and waits for trustee state transitions. CPU down operation no longer waits for works to be drained but trustee sticks around till all pending works have been completed. If CPU is brought back up while works are still draining, workqueue_cpu_callback() tells trustee to step down and tell workers to rebind to the cpu. As it's difficult to tell whether cwqs are empty if it's freezing or frozen, trustee doesn't consider draining to be complete while a gcwq is freezing or frozen (tracked by new GCWQ_FREEZING flag). Also, workers which get unbound from their cpu are marked with WORKER_ROGUE. Trustee based implementation doesn't bring any new feature at this point but it will be used to manage worker pool when dynamic shared worker pool is implemented. Signed-off-by: Tejun Heo

sched: adjust when cpu_active and cpuset configurations are updated during cpu on/offlining

2010-06-08T19:40:36Z

Currently, when a cpu goes down, cpu_active is cleared before CPU_DOWN_PREPARE starts and cpuset configuration is updated from a default priority cpu notifier. When a cpu is coming up, it's set before CPU_ONLINE but cpuset configuration again is updated from the same cpu notifier. For cpu notifiers, this presents an inconsistent state. Threads which a CPU_DOWN_PREPARE notifier expects to be bound to the CPU can be migrated to other cpus because the cpu is no more inactive. Fix it by updating cpu_active in the highest priority cpu notifier and cpuset configuration in the second highest when a cpu is coming up. Down path is updated similarly. This guarantees that all other cpu notifiers see consistent cpu_active and cpuset configuration. cpuset_track_online_cpus() notifier is converted to cpuset_update_active_cpus() which just updates the configuration and now called from cpuset_cpu_[in]active() notifiers registered from sched_init_smp(). If cpuset is disabled, cpuset_update_active_cpus() degenerates into partition_sched_domains() making separate notifier for !CONFIG_CPUSETS unnecessary. This problem is triggered by cmwq. During CPU_DOWN_PREPARE, hotplug callback creates a kthread and kthread_bind()s it to the target cpu, and the thread is expected to run on that cpu. * Ingo's test discovered __cpuinit/exit markups were incorrect. Fixed. Signed-off-by: Tejun Heo Acked-by: Peter Zijlstra Cc: Rusty Russell Cc: Ingo Molnar Cc: Paul Menage

sched: define and use CPU_PRI_* enums for cpu notifier priorities

2010-06-08T19:40:36Z

Instead of hardcoding priority 10 and 20 in sched and perf, collect them into CPU_PRI_* enums. Signed-off-by: Tejun Heo Acked-by: Peter Zijlstra Cc: Rusty Russell Cc: Paul Mackerras Cc: Ingo Molnar Cc: Arnaldo Carvalho de Melo

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

2009-12-09T06:09:36Z

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

2009-12-09T06:09:33Z

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