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Diffstat (limited to 'Documentation/RCU/checklist.rst')
| -rw-r--r-- | Documentation/RCU/checklist.rst | 41 |
1 files changed, 27 insertions, 14 deletions
diff --git a/Documentation/RCU/checklist.rst b/Documentation/RCU/checklist.rst index 7de3e308f330..4b30f701225f 100644 --- a/Documentation/RCU/checklist.rst +++ b/Documentation/RCU/checklist.rst @@ -69,7 +69,13 @@ over a rather long period of time, but improvements are always welcome! Explicit disabling of preemption (preempt_disable(), for example) can serve as rcu_read_lock_sched(), but is less readable and prevents lockdep from detecting locking issues. Acquiring a - spinlock also enters an RCU read-side critical section. + raw spinlock also enters an RCU read-side critical section. + + The guard(rcu)() and scoped_guard(rcu) primitives designate + the remainder of the current scope or the next statement, + respectively, as the RCU read-side critical section. Use of + these guards can be less error-prone than rcu_read_lock(), + rcu_read_unlock(), and friends. Please note that you *cannot* rely on code known to be built only in non-preemptible kernels. Such code can and will break, @@ -405,15 +411,19 @@ over a rather long period of time, but improvements are always welcome! 13. Unlike most flavors of RCU, it *is* permissible to block in an SRCU read-side critical section (demarked by srcu_read_lock() and srcu_read_unlock()), hence the "SRCU": "sleepable RCU". - Please note that if you don't need to sleep in read-side critical - sections, you should be using RCU rather than SRCU, because RCU - is almost always faster and easier to use than is SRCU. - - Also unlike other forms of RCU, explicit initialization and - cleanup is required either at build time via DEFINE_SRCU() - or DEFINE_STATIC_SRCU() or at runtime via init_srcu_struct() - and cleanup_srcu_struct(). These last two are passed a - "struct srcu_struct" that defines the scope of a given + As with RCU, guard(srcu)() and scoped_guard(srcu) forms are + available, and often provide greater ease of use. Please note + that if you don't need to sleep in read-side critical sections, + you should be using RCU rather than SRCU, because RCU is almost + always faster and easier to use than is SRCU. + + Also unlike other forms of RCU, explicit initialization + and cleanup is required either at build time via + DEFINE_SRCU(), DEFINE_STATIC_SRCU(), DEFINE_SRCU_FAST(), + or DEFINE_STATIC_SRCU_FAST() or at runtime via either + init_srcu_struct() or init_srcu_struct_fast() and + cleanup_srcu_struct(). These last three are passed a + `struct srcu_struct` that defines the scope of a given SRCU domain. Once initialized, the srcu_struct is passed to srcu_read_lock(), srcu_read_unlock() synchronize_srcu(), synchronize_srcu_expedited(), and call_srcu(). A given @@ -443,10 +453,13 @@ over a rather long period of time, but improvements are always welcome! real-time workloads than is synchronize_rcu_expedited(). It is also permissible to sleep in RCU Tasks Trace read-side - critical section, which are delimited by rcu_read_lock_trace() and - rcu_read_unlock_trace(). However, this is a specialized flavor - of RCU, and you should not use it without first checking with - its current users. In most cases, you should instead use SRCU. + critical section, which are delimited by rcu_read_lock_trace() + and rcu_read_unlock_trace(). However, this is a specialized + flavor of RCU, and you should not use it without first checking + with its current users. In most cases, you should instead + use SRCU. As with RCU and SRCU, guard(rcu_tasks_trace)() and + scoped_guard(rcu_tasks_trace) are available, and often provide + greater ease of use. Note that rcu_assign_pointer() relates to SRCU just as it does to other forms of RCU, but instead of rcu_dereference() you should |