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| author | Gautham R Shenoy <ego@in.ibm.com> | 2008-01-25 23:08:02 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-01-25 23:08:02 +0300 |
| commit | 86ef5c9a8edd78e6bf92879f32329d89b2d55b5a (patch) | |
| tree | 7bf46885326a6fdbb0c3596855408e9a5634dd3a /Documentation | |
| parent | d221938c049f4845da13c8593132595a6b9222a8 (diff) | |
| download | linux-86ef5c9a8edd78e6bf92879f32329d89b2d55b5a.tar.xz | |
cpu-hotplug: replace lock_cpu_hotplug() with get_online_cpus()
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 <ego@in.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/cpu-hotplug.txt | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt index a741f658a3c9..fb94f5a71b68 100644 --- a/Documentation/cpu-hotplug.txt +++ b/Documentation/cpu-hotplug.txt @@ -109,12 +109,13 @@ Never use anything other than cpumask_t to represent bitmap of CPUs. for_each_cpu_mask(x,mask) - Iterate over some random collection of cpu mask. #include <linux/cpu.h> - lock_cpu_hotplug() and unlock_cpu_hotplug(): + get_online_cpus() and put_online_cpus(): -The above calls are used to inhibit cpu hotplug operations. While holding the -cpucontrol mutex, cpu_online_map will not change. If you merely need to avoid -cpus going away, you could also use preempt_disable() and preempt_enable() -for those sections. Just remember the critical section cannot call any +The above calls are used to inhibit cpu hotplug operations. While the +cpu_hotplug.refcount is non zero, the cpu_online_map will not change. +If you merely need to avoid cpus going away, you could also use +preempt_disable() and preempt_enable() for those sections. +Just remember the critical section cannot call any function that can sleep or schedule this process away. The preempt_disable() will work as long as stop_machine_run() is used to take a cpu down. |