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- ============
- LITMUS TESTS
- ============
- Each subdirectory contains litmus tests that are typical to describe the
- semantics of respective kernel APIs.
- For more information about how to "run" a litmus test or how to generate
- a kernel test module based on a litmus test, please see
- tools/memory-model/README.
- atomic (/atomic directory)
- --------------------------
- Atomic-RMW+mb__after_atomic-is-stronger-than-acquire.litmus
- Test that an atomic RMW followed by a smp_mb__after_atomic() is
- stronger than a normal acquire: both the read and write parts of
- the RMW are ordered before the subsequential memory accesses.
- Atomic-RMW-ops-are-atomic-WRT-atomic_set.litmus
- Test that atomic_set() cannot break the atomicity of atomic RMWs.
- NOTE: Require herd7 7.56 or later which supports "(void)expr".
- cmpxchg-fail-ordered-1.litmus
- Demonstrate that a failing cmpxchg() operation acts as a full barrier
- when followed by smp_mb__after_atomic().
- cmpxchg-fail-ordered-2.litmus
- Demonstrate that a failing cmpxchg() operation acts as an acquire
- operation when followed by smp_mb__after_atomic().
- cmpxchg-fail-unordered-1.litmus
- Demonstrate that a failing cmpxchg() operation does not act as a
- full barrier.
- cmpxchg-fail-unordered-2.litmus
- Demonstrate that a failing cmpxchg() operation does not act as an
- acquire operation.
- locking (/locking directory)
- ----------------------------
- DCL-broken.litmus
- Demonstrates that double-checked locking needs more than just
- the obvious lock acquisitions and releases.
- DCL-fixed.litmus
- Demonstrates corrected double-checked locking that uses
- smp_store_release() and smp_load_acquire() in addition to the
- obvious lock acquisitions and releases.
- RM-broken.litmus
- Demonstrates problems with "roach motel" locking, where code is
- freely moved into lock-based critical sections. This example also
- shows how to use the "filter" clause to discard executions that
- would be excluded by other code not modeled in the litmus test.
- Note also that this "roach motel" optimization is emulated by
- physically moving P1()'s two reads from x under the lock.
- What is a roach motel? This is from an old advertisement for
- a cockroach trap, much later featured in one of the "Men in
- Black" movies. "The roaches check in. They don't check out."
- RM-fixed.litmus
- The counterpart to RM-broken.litmus, showing P0()'s two loads from
- x safely outside of the critical section.
- RCU (/rcu directory)
- --------------------
- MP+onceassign+derefonce.litmus (under tools/memory-model/litmus-tests/)
- Demonstrates the use of rcu_assign_pointer() and rcu_dereference() to
- ensure that an RCU reader will not see pre-initialization garbage.
- RCU+sync+read.litmus
- RCU+sync+free.litmus
- Both the above litmus tests demonstrate the RCU grace period guarantee
- that an RCU read-side critical section can never span a grace period.
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