Mathieu Desnoyers wrote:
Thread Migration Preemption
This patch adds the ability to protect critical sections from migration to
another CPU without disabling preemption.
This will be useful to minimize the amount of preemption disabling for the -rt
patch. It will help leveraging improvements brought by the local_t types in
asm/local.h (see Documentation/local_ops.txt). Note that the updates done to
variables protected by migration_disable must be either atomic or protected from
concurrent updates done by other threads.
Typical use:
migration_disable();
local_inc(&__get_cpu_var(&my_local_t_var));
migration_enable();
Which will increment the variable atomically wrt the local CPU.
Comments (such as how to integrate this in the already almost full
preempt_count) are welcome.
This seems like way too much stuff to add just for this type of thing. Why
not just disable and reenable preempt? Surely local_inc is not going to take
so long that disabling preemption matters.
The task struct is not something we should just be carefree putting crap
into because it is seemingly free :(
--
SUSE Labs, Novell Inc.
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