Messages in this thread | | | Date | Mon, 1 Nov 2004 07:00:07 -0700 (MST) | From | Zwane Mwaikambo <> | Subject | Re: [PATCH] [CPU-HOTPLUG] convert cpucontrol to be a rwsem |
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On Mon, 1 Nov 2004, Dominik Brodowski wrote:
> [CPU-HOTPLUG] Use a rw-semaphore for serializing and locking > > Currently, lock_cpu_hotplug serializes multiple calls to cpufreq->target() > on multiple CPUs even though that's unneccessary. Even further, it > serializes these calls with totally unrelated other parts of the kernel... > some ppc64 event reporting, some cache management, and so on. In my opinion > locking should be done subsystem (and normally data-)specific, and disabling > CPU hotplug should just do that. > > This patch converts the semaphore cpucontrol to be a rwsem which allows us > to use it for _both_ variants: locking (write) and (multiple) other parts > disabling CPU hotplug (read). > > Only problem I see with this approach is that lock_cpu_hotplug_interruptible() > needs to disappear as there is no down_write_interruptible() for rw-semaphores. > > Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.de>
Agreed it makes a lot more sense, i think there could be some places where we use preempt_disable to protect against cpu offline which could converted, but that can come later.
Thanks, Zwane
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