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documentation: Composability analogies
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This commit expands on RCU's composability by comparing it to that of
transactional memory and of locking.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Paul E. McKenney committed Dec 5, 2015
1 parent 01d3ad3 commit 0825458
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8 changes: 8 additions & 0 deletions Documentation/RCU/Design/Requirements/Requirements.html
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Expand Up @@ -1494,6 +1494,14 @@ <h3><a name="Composability">Composability</a></h3>
section, neither of which is conducive to a long-lived and prosperous
kernel.

<p>
It is worth noting that RCU is not alone in limiting composability.
For example, many transactional-memory implementations prohibit
composing a pair of transactions separated by an irrevocable
operation (for example, a network receive operation).
For another example, lock-based critical sections can be composed
surprisingly freely, but only if deadlock is avoided.

<p>
In short, although RCU read-side critical sections are highly composable,
care is required in some situations, just as is the case for any other
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8 changes: 8 additions & 0 deletions Documentation/RCU/Design/Requirements/Requirements.htmlx
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Expand Up @@ -1653,6 +1653,14 @@ in RCU implicitly splitting the enclosing RCU read-side critical
section, neither of which is conducive to a long-lived and prosperous
kernel.

<p>
It is worth noting that RCU is not alone in limiting composability.
For example, many transactional-memory implementations prohibit
composing a pair of transactions separated by an irrevocable
operation (for example, a network receive operation).
For another example, lock-based critical sections can be composed
surprisingly freely, but only if deadlock is avoided.

<p>
In short, although RCU read-side critical sections are highly composable,
care is required in some situations, just as is the case for any other
Expand Down

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