kernel/linux.git/include/linux/cpu.h, branch v2.6.30

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

cpu-hotplug: replace lock_cpu_hotplug() with get_online_cpus()

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

Replace all lock_cpu_hotplug/unlock_cpu_hotplug from the kernel and use get_online_cpus and put_online_cpus instead as it highlights the refcount semantics in these operations. The new API guarantees protection against the cpu-hotplug operation, but it doesn't guarantee serialized access to any of the local data structures. Hence the changes needs to be reviewed. In case of pseries_add_processor/pseries_remove_processor, use cpu_maps_update_begin()/cpu_maps_update_done() as we're modifying the cpu_present_map there. Signed-off-by: Gautham R Shenoy Signed-off-by: Ingo Molnar

cpu-hotplug: refcount based cpu hotplug

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

This patch implements a Refcount + Waitqueue based model for cpu-hotplug. Now, a thread which wants to prevent cpu-hotplug, will bump up a global refcount and the thread which wants to perform a cpu-hotplug operation will block till the global refcount goes to zero. The readers, if any, during an ongoing cpu-hotplug operation are blocked until the cpu-hotplug operation is over. Signed-off-by: Gautham R Shenoy Signed-off-by: Paul Jackson [For !CONFIG_HOTPLUG_CPU ] Signed-off-by: Ingo Molnar

CPU hotplug: fix cpu_is_offline() on !CONFIG_HOTPLUG_CPU

2008-01-06T20:39:42+00:00

make randconfig bootup testing found that the cpufreq code crashes on bootup, if the powernow-k8 driver is enabled and if maxcpus=1 passed on the boot line to a !CONFIG_HOTPLUG_CPU kernel. First lockdep found out that there's an inconsistent unlock sequence: ===================================== [ BUG: bad unlock balance detected! ] ------------------------------------- swapper/1 is trying to release lock (&per_cpu(cpu_policy_rwsem, cpu)) at: [] unlock_policy_rwsem_write+0x3c/0x42 but there are no more locks to release! Call Trace: [] unlock_policy_rwsem_write+0x3c/0x42 [] print_unlock_inbalance_bug+0x104/0x12c [] mark_held_locks+0x56/0x94 [] unlock_policy_rwsem_write+0x3c/0x42 [] cpufreq_add_dev+0x2a8/0x5c4 ... then shortly afterwards the cpufreq code crashed on an assert: ------------[ cut here ]------------ kernel BUG at drivers/cpufreq/cpufreq.c:1068! invalid opcode: 0000 [1] SMP [...] Call Trace: [] sysdev_driver_unregister+0x5b/0x91 [] cpufreq_register_driver+0x15d/0x1a2 [] powernowk8_init+0x86/0x94 [...] ---[ end trace 1e9219be2b4431de ]--- the bug was caused by maxcpus=1 bootup, which brought up the secondary core as !cpu_online() but !cpu_is_offline() either, which on on !CONFIG_HOTPLUG_CPU is always 0 (include/linux/cpu.h): /* CPUs don't go offline once they're online w/o CONFIG_HOTPLUG_CPU */ static inline int cpu_is_offline(int cpu) { return 0; } but the cpufreq code uses cpu_online() and cpu_is_offline() in a mixed way - the low-level drivers use cpu_online(), while the cpufreq core uses cpu_is_offline(). This opened up the possibility to add the non-initialized sysdev device of the secondary core: cpufreq-core: trying to register driver powernow-k8 cpufreq-core: adding CPU 0 powernow-k8: BIOS error - no PSB or ACPI _PSS objects cpufreq-core: initialization failed cpufreq-core: adding CPU 1 cpufreq-core: initialization failed which then blew up. The fix is to make cpu_is_offline() always the negation of cpu_online(). With that fix applied the kernel boots up fine without crashing: Calling initcall 0xffffffff80cc0510: powernowk8_init+0x0/0x94() powernow-k8: Found 1 AMD Athlon(tm) 64 X2 Dual Core Processor 3800+ processors (1 cpu cores) (version 2.20.00) powernow-k8: BIOS error - no PSB or ACPI _PSS objects initcall 0xffffffff80cc0510: powernowk8_init+0x0/0x94() returned -19. initcall 0xffffffff80cc0510 ran for 19 msecs: powernowk8_init+0x0/0x94() Calling initcall 0xffffffff80cc328f: init_lapic_nmi_sysfs+0x0/0x39() We could fix this by making CPU enumeration aware of max_cpus, but that would be more fragile IMO, and the cpu_online(cpu) != cpu_is_offline(cpu) possibility was quite confusing and a continuous source of bugs too. Most distributions have kernels with CPU hotplug enabled, so this bug remained hidden for a long time. Bug forensics: The broken cpu_is_offline() API variant was introduced via: commit a59d2e4e6977e7b94e003c96a41f07e96cddc340 Author: Rusty Russell Date: Mon Mar 8 06:06:03 2004 -0800 [PATCH] minor cleanups for hotplug CPUs ( this predates linux-2.6.git, this commit is available from Thomas's historic git tree. ) Then 1.5 years later the cpufreq code made use of it: commit c32b6b8e524d2c337767d312814484d9289550cf Author: Ashok Raj Date: Sun Oct 30 14:59:54 2005 -0800 [PATCH] create and destroy cpufreq sysfs entries based on cpu notifiers + if (cpu_is_offline(cpu)) + return 0; which is a correct use of the subtly broken new API. v2.6.15 then shipped with this bug included. then it took two more years for random-kernel qa to hit it. Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar Signed-off-by: Linus Torvalds

Redefine {un}register_hotcpu_notifier() !HOTPLUG_CPU stubs

2007-10-18T21:37:28+00:00

The return of the present "do {} while" based stub definition of register_hotcpu_notifier() cannot be checked. This makes the stub asymmetric w.r.t. the real HOTPLUG_CPU=y implementation that is int-returning. So let us redefine this to be consistent with the full version. Also do the same for unregister_hotcpu_notifier(). We cannot define these as static inline functions due to an existing GCC bug (#33172). So define as macros that return appropriately instead (int '0' for the register_hotcpu_notifier case and void for unregister_hotcpu_notifier). Signed-off-by: Satyam Sharma Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds