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Re: [RFC/PATCH] replace preempt_* calls with rcu_read_* variants
- From: Keshavamurthy Anil S <anil dot s dot keshavamurthy at intel dot com>
- To: Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>
- Cc: SystemTAP <systemtap at sources dot redhat dot com>
- Date: Tue, 14 Mar 2006 14:12:08 -0800
- Subject: Re: [RFC/PATCH] replace preempt_* calls with rcu_read_* variants
- References: <20060314134415.GA16136@in.ibm.com>
- Reply-to: Keshavamurthy Anil S <anil dot s dot keshavamurthy at intel dot com>
On Tue, Mar 14, 2006 at 05:44:15AM -0800, Ananth N Mavinakayanahalli wrote:
>
> Hi,
>
> Can somebody please remind me why we are not using
> rcu_read_unlock/lock()
> to RCU protect the kprobe handlers, instead, are using
> preempt_disable/enable()?
"In some realtime-friendly RCU implementations, the RCU read-side critical
sections do not disable preemption. So, if you are using synchronize_sched()
on the update side, you need to use preempt_disable() (or some other
primitive that disables preemption, for example, any of the primitives
that disables hardware interrupts) on the read side."
http://www.ussg.iu.edu/hypermail/linux/kernel/0510.2/0537.html
-thanks,
-Anil