Messages in this thread | | | Date | Thu, 06 Dec 2012 00:21:06 +0530 | From | "Srivatsa S. Bhat" <> | Subject | Re: [RFC PATCH v2 01/10] CPU hotplug: Provide APIs for "light" atomic readers to prevent CPU offline |
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Replaying what Oleg wrote:
Hi,
Sorry I don't understand the context and I can't find this thread anywhere, so I am not sure I understand...
> Replaying what Tejun wrote: > So, we basically need percpu_rwlock. We already have percpu_rwsem.
Yes, and with -mm patches it becomes reader-friendly. In particular see http://marc.info/?l=linux-mm-commits&m=135240650828875
> Oleg, it seems > CPU hotplug needs big-reader rwlock, ideas on how to proceed? >
I am going to convert get_online_cpus() to use percpu_down_read(), this looks simple.
We already discussed this with Paul, see
http://marc.info/?l=linux-kernel&m=135248463226031
and the whole thread.
In short, all we need is percpu_down_write_recursive_readers() and afaics the only complication is lockdep, we need down_read_no_lockdep() which (like __up_read) doesn't do rwsem_acquire_read().
Oleg.
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