Document the fact that RCU callbacks can run in parallel
Add an item to the RCU documentation checklist noting that RCU callbacks can run in parallel. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -222,7 +222,15 @@ over a rather long period of time, but improvements are always welcome!
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deadlock as soon as the RCU callback happens to interrupt that
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deadlock as soon as the RCU callback happens to interrupt that
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acquisition's critical section.
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acquisition's critical section.
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13. SRCU (srcu_read_lock(), srcu_read_unlock(), and synchronize_srcu())
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13. RCU callbacks can be and are executed in parallel. In many cases,
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the callback code simply wrappers around kfree(), so that this
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is not an issue (or, more accurately, to the extent that it is
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an issue, the memory-allocator locking handles it). However,
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if the callbacks do manipulate a shared data structure, they
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must use whatever locking or other synchronization is required
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to safely access and/or modify that data structure.
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14. SRCU (srcu_read_lock(), srcu_read_unlock(), and synchronize_srcu())
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may only be invoked from process context. Unlike other forms of
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may only be invoked from process context. Unlike other forms of
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RCU, it -is- permissible to block in an SRCU read-side critical
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RCU, it -is- permissible to block in an SRCU read-side critical
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section (demarked by srcu_read_lock() and srcu_read_unlock()),
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section (demarked by srcu_read_lock() and srcu_read_unlock()),
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