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author | Linus Torvalds <torvalds@linux-foundation.org> | 2009-12-17 17:00:20 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-12-17 17:00:20 -0800 |
commit | 55db493b65c7b6bb5d7bd3dd3c8a2fe13f5dc09c (patch) | |
tree | 7f9203f43e7c81687c9aaa0213266bc7b2e89e35 /Documentation | |
parent | efc8e7f4c83dc85acbf5f54a8b1b24ae75b20aaa (diff) | |
parent | a4636818f8e0991f32d9528f39cf4f3d6a7d30a3 (diff) | |
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Merge branch 'cpumask-cleanups' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus
* 'cpumask-cleanups' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus:
cpumask: rename tsk_cpumask to tsk_cpus_allowed
cpumask: don't recommend set_cpus_allowed hack in Documentation/cpu-hotplug.txt
cpumask: avoid dereferencing struct cpumask
cpumask: convert drivers/idle/i7300_idle.c to cpumask_var_t
cpumask: use modern cpumask style in drivers/scsi/fcoe/fcoe.c
cpumask: avoid deprecated function in mm/slab.c
cpumask: use cpu_online in kernel/perf_event.c
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/cpu-hotplug.txt | 49 |
1 files changed, 17 insertions, 32 deletions
diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt index 4d4a644b505e..a99d7031cdf9 100644 --- a/Documentation/cpu-hotplug.txt +++ b/Documentation/cpu-hotplug.txt @@ -315,41 +315,26 @@ A: The following are what is required for CPU hotplug infrastructure to work Q: I need to ensure that a particular cpu is not removed when there is some work specific to this cpu is in progress. -A: First switch the current thread context to preferred cpu +A: There are two ways. If your code can be run in interrupt context, use + smp_call_function_single(), otherwise use work_on_cpu(). Note that + work_on_cpu() is slow, and can fail due to out of memory: int my_func_on_cpu(int cpu) { - cpumask_t saved_mask, new_mask = CPU_MASK_NONE; - int curr_cpu, err = 0; - - saved_mask = current->cpus_allowed; - cpu_set(cpu, new_mask); - err = set_cpus_allowed(current, new_mask); - - if (err) - return err; - - /* - * If we got scheduled out just after the return from - * set_cpus_allowed() before running the work, this ensures - * we stay locked. - */ - curr_cpu = get_cpu(); - - if (curr_cpu != cpu) { - err = -EAGAIN; - goto ret; - } else { - /* - * Do work : But cant sleep, since get_cpu() disables preempt - */ - } - ret: - put_cpu(); - set_cpus_allowed(current, saved_mask); - return err; - } - + int err; + get_online_cpus(); + if (!cpu_online(cpu)) + err = -EINVAL; + else +#if NEEDS_BLOCKING + err = work_on_cpu(cpu, __my_func_on_cpu, NULL); +#else + smp_call_function_single(cpu, __my_func_on_cpu, &err, + true); +#endif + put_online_cpus(); + return err; + } Q: How do we determine how many CPUs are available for hotplug. A: There is no clear spec defined way from ACPI that can give us that |