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2020-06-29Documentation/litmus-tests: Add note on herd7 7.56 in atomic litmus testAkira Yokosawa2-0/+2
herdtools 7.56 has enhanced herd7's C parser so that the "(void)expr" construct in Atomic-RMW-ops-are-atomic-WRT-atomic_set.litmus is accepted. This is independent of LKMM's cat model, so mention the required version in the header of the litmus test and its entry in README. CC: Boqun Feng <boqun.feng@gmail.com> Reported-by: Andrea Parri <parri.andrea@gmail.com> Acked-by: Andrea Parri <parri.andrea@gmail.com> Signed-off-by: Akira Yokosawa <akiyks@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-29Documentation/litmus-tests: Cite an RCU litmus testJoel Fernandes (Google)1-0/+4
This commit cites a pertinent RCU-related litmus test. Co-developed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Co-developed-by: Akira Yokosawa <akiyks@gmail.com> [Alan: grammar nit] [ paulmck: Update commit log and title per Akira feedback. ] Suggested-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Akira Yokosawa <akiyks@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-29Documentation/litmus-tests: Merge atomic's README into top-level oneAkira Yokosawa2-16/+19
Where Documentation/litmus-tests/README lists RCU litmus tests, Documentation/litmus-tests/atomic/README lists atomic litmus tests. For symmetry, merge the latter into former, with some context adjustment in the introduction. Acked-by: Andrea Parri <parri.andrea@gmail.com> Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org> Acked-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Akira Yokosawa <akiyks@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-29Documentation/litmus-tests/atomic: Add a test for smp_mb__after_atomic()Boqun Feng2-0/+37
We already use a litmus test in atomic_t.txt to describe atomic RMW + smp_mb__after_atomic() is stronger than acquire (both the read and the write parts are ordered). So make it a litmus test in atomic-tests directory, so that people can access the litmus easily. Additionally, change the processor numbers "P1, P2" to "P0, P1" in atomic_t.txt for the consistency with the processor numbers in the litmus test, which herd can handle. Acked-by: Alan Stern <stern@rowland.harvard.edu> Acked-by: Andrea Parri <parri.andrea@gmail.com> Signed-off-by: Boqun Feng <boqun.feng@gmail.com> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-29Documentation/litmus-tests/atomic: Add a test for atomic_set()Boqun Feng2-0/+31
We already use a litmus test in atomic_t.txt to describe the behavior of an atomic_set() with the an atomic RMW, so add it into atomic-tests directory to make it easily accessible for anyone who cares about the semantics of our atomic APIs. Besides currently the litmus test "atomic-set" in atomic_t.txt has a few things to be improved: 1) The CPU/Processor numbers "P1,P2" are not only inconsistent with the rest of the document, which uses "CPU0" and "CPU1", but also unacceptable by the herd tool, which requires processors start at "P0". 2) The initialization block uses a "atomic_set()", which is OK, but it's better to use ATOMIC_INIT() to make clear this is an initialization. 3) The return value of atomic_add_unless() is discarded inexplicitly, which is OK for C language, but it will be helpful to the herd tool if we use a void cast to make the discard explicit. 4) The name and the paragraph describing the test need to be more accurate and aligned with our wording in LKMM. Therefore fix these in both atomic_t.txt and the new added litmus test. Acked-by: Andrea Parri <parri.andrea@gmail.com> Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Boqun Feng <boqun.feng@gmail.com> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-29Documentation/litmus-tests: Introduce atomic directoryBoqun Feng1-0/+4
Although we have atomic_t.txt and its friends to describe the semantics of atomic APIs and lib/atomic64_test.c for build testing and testing in UP mode, the tests for our atomic APIs in real SMP mode are still missing. Since now we have the LKMM tool in kernel and litmus tests can be used to generate kernel modules for testing purpose with "klitmus" (a tool from the LKMM toolset), it makes sense to put a few typical litmus tests into kernel so that 1) they are the examples to describe the conceptual mode of the semantics of atomic APIs, and 2) they can be used to generate kernel test modules for anyone who is interested to test the atomic APIs implementation (in most cases, is the one who implements the APIs for a new arch) Therefore, introduce the atomic directory for this purpose. The directory is maintained by the LKMM group to make sure the litmus tests are always aligned with our memory model. Acked-by: Alan Stern <stern@rowland.harvard.edu> Acked-by: Andrea Parri <parri.andrea@gmail.com> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-29Documentation: LKMM: Add litmus test for RCU GP guarantee where reader storesJoel Fernandes (Google)2-0/+48
This adds an example for the important RCU grace period guarantee, which shows an RCU reader can never span a grace period. Acked-by: Andrea Parri <parri.andrea@gmail.com> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-29Documentation: LKMM: Add litmus test for RCU GP guarantee where updater ↵Joel Fernandes (Google)1-0/+42
frees object This adds an example for the important RCU grace period guarantee, which shows an RCU reader can never span a grace period. Acked-by: Andrea Parri <parri.andrea@gmail.com> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>