Messages in this thread | | | Subject | Re: [rfc] "fair" rw spinlocks | From | Andi Kleen <> | Date | Sat, 28 Nov 2009 12:15:07 +0100 |
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"Paul E. McKenney" <paulmck@linux.vnet.ibm.com> writes: > > The usual trick would be to keep per-fair-rwlock state in per-CPU > variables. If it is forbidden to read-acquire one nestable fair rwlock > while read-holding another, then this per-CPU state can be a single > pointer and a nesting count. On the other hand, if it is permitted to > read-acquire one nestable fair rwlock while holding another, then one > can use a small per-CPU array of pointer/count pairs.
The problem is that in preemptible kernels kernel threads can switch CPUs all the time. How would you sync the per CPU state then?
-Andi -- ak@linux.intel.com -- Speaking for myself only.
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