-CDSChecker Readme
-=================
+C11Tester: A Testing tool for C11 and C++11 Atomics
+=====================================================
-Copyright © 2013 Regents of the University of California. All rights reserved.
+C11Tester is a testing tool for C11/C++11 which randomly explores the
+behaviors of code under the C/C++ memory model.
-CDSChecker is distributed under the GPL v2. See the LICENSE file for details.
-
-
-Overview
---------
-
-CDSChecker is a model checker for C11/C++11 which exhaustively explores the
-behaviors of code under the C/C++ memory model. It uses partial order reduction
-as well as a few other novel techniques to eliminate time spent on redundant
-execution behaviors and to significantly shrink the state space. The model
-checking algorithm is described in more detail in this paper (published in
-OOPSLA '13):
-
- <http://demsky.eecs.uci.edu/publications/c11modelcheck.pdf>
-
-It is designed to support unit tests on concurrent data structure written using
-C/C++ atomics.
-
-CDSChecker is constructed as a dynamically-linked shared library which
+C11Tester is constructed as a dynamically-linked shared library which
implements the C and C++ atomic types and portions of the other thread-support
-libraries of C/C++ (e.g., std::atomic, std::mutex, etc.). Notably, we only
-support the C version of threads (i.e., `thrd_t` and similar, from `<threads.h>`),
-because C++ threads require features which are only available to a C++11
-compiler (and we want to support others, at least for now).
+libraries of C/C++ (e.g., std::atomic, std::mutex, etc.).
+
+C11Tester compiles on Linux. Instrumenting programs requires using
+our LLVM pass. It likely can be ported to other \*NIX flavors.
-CDSChecker should compile on Linux and Mac OSX with no dependencies and has been
-tested with LLVM (clang/clang++) and GCC. It likely can be ported to other \*NIX
-flavors. We have not attempted to port to Windows.
+Mailing List
+------------
-You may also refer to the CDSChecker project page:
+If you have questions, you can contact us at c11tester@googlegroups.com.
- <http://demsky.eecs.uci.edu/c11modelchecker.php>
+You can sign up for the C11Tester mailing list at:
+<https://groups.google.com/forum/#!forum/c11tester>
Getting Started
---------------
-If you haven't done so already, you may download CDSChecker using
-[git](http://git-scm.com/):
+If you haven't done so already, you may download C11Tester using git:
- git clone git://demsky.eecs.uci.edu/model-checker.git
+ git clone git://plrg.eecs.uci.edu/c11tester.git
Get the benchmarks (not required; distributed separately):
- cd model-checker
- git clone git://demsky.eecs.uci.edu/model-checker-benchmarks.git benchmarks
-
-Compile the model checker:
+ git clone git://plrg.eecs.uci.edu/c11concurrency-benchmarks.git
- make
-
-Compile the benchmarks:
+Get the LLVM frontend using git and follow its directions to build:
- make benchmarks
+ git clone git://plrg.eecs.uci.edu/c11llvm.git
-Run a simple example (the `run.sh` script does some very minimal processing for
-you):
+Compile the fuzzer:
- ./run.sh test/userprog.o
+ make
-To see the help message on how to run CDSChecker, execute:
+To see the help message on how to run C11Tester, execute:
./run.sh -h
Useful Options
--------------
-`-m num`
-
- > Controls the liveness of the memory system. Note that multithreaded programs
- > often rely on memory liveness for termination, so this parameter is
- > necessary for such programs.
- >
- > Liveness is controlled by `num`: the number of times a load is allowed to
- > see the same store when a newer store exists---one that is ordered later in
- > the modification order.
-
-`-y`
-
- > Turns on CHESS-like yield-based fairness support (requires `thrd_yield()`
- > instrumentation in test program).
-
-`-f num`
-
- > Turns on alternative fairness support (less desirable than `-y`).
-
`-v`
> Verbose: show all executions and not just buggy ones.
-`-s num`
-
- > Constrain how long we will run to wait for a future value past when it is
- > expected
-
-`-u num`
-
- > Value to provide to atomics loads from uninitialized memory locations. The
- > default is 0, but this may cause some programs to throw exceptions
- > (segfault) before the model checker prints a trace.
-
-Suggested options:
-
-> -m 2 -y
-
-or
-
-> -m 2 -f 10
+`-x num`
+ > Specify the number number of executions to run.
Benchmarks
-------------------
-Many simple tests are located in the `tests/` directory. You may also want to
-try the larger benchmarks (distributed separately), which can be placed under
-the `benchmarks/` directory. After building CDSChecker, you can build and run
-the benchmarks as follows:
+Many simple tests are located in the `test/` directory. These are
+manually instrumented and can just be run.
-> make benchmarks
-> cd benchmarks
-> ./run.sh barrier/barrier -y -m 2 # runs barrier test with fairness/memory liveness
-> ./bench.sh # run all benchmarks and provide timing results
+You may also want to try the larger benchmarks (distributed
+separately). These require LLVM to instrument.
Running your own code
---------------------
-You likely want to test your own code, not just our simple tests. To do so, you
-need to perform a few steps.
-
-First, because CDSChecker executes your program dozens (if not hundreds or
-thousands) of times, you will have the most success if your code is written as a
-unit test and not as a full-blown program.
-
-Second, because CDSChecker must be able to manage your program for you, your
-program should declare its main entry point as `user_main(int, char**)` rather
-than `main(int, char**)`.
-
-Third, test programs should use the standard C11/C++11 library headers
-(`<atomic>`/`<stdatomic.h>`, `<mutex>`, `<condition_variable>`, `<thread.h>`).
-As of now, we only support C11 thread syntax (`thrd_t`, etc. from
-`<thread.h>`).
-
-Test programs may also use our included happens-before race detector by
-including <librace.h> and utilizing the appropriate functions
-(`store_{8,16,32,64}()` and `load_{8,16,32,64}()`) for loading/storing data from/to
-non-atomic shared memory.
-
-CDSChecker can also check boolean assertions in your test programs. Just
-include `<model-assert.h>` and use the `MODEL_ASSERT()` macro in your test program.
-CDSChecker will report a bug in any possible execution in which the argument to
-`MODEL_ASSERT()` evaluates to false (that is, 0).
+You likely want to test your own code, not just our tests. You will
+likely need to use our LLVM pass to instrument your program. You will
+have to modify your build environment to do this.
-Test programs should be compiled against our shared library (libmodel.so) using
-the headers in the `include/` directory. Then the shared library must be made
-available to the dynamic linker, using the `LD_LIBRARY_PATH` environment
-variable, for instance.
+Test programs should be compiled against our shared library
+(libmodel.so). Then the shared library must be made available to the
+dynamic linker, using the `LD_LIBRARY_PATH` environment variable, for
+instance.
Reading an execution trace
--------------------------
-When CDSChecker detects a bug in your program (or when run with the `--verbose`
+When C11Tester detects a bug in your program (or when run with the `--verbose`
flag), it prints the output of the program run (STDOUT) along with some summary
trace information for the execution in question. The trace is given as a
sequence of lines, where each line represents an operation in the execution
-trace. These lines are ordered by the order in which they were run by CDSChecker
+trace. These lines are ordered by the order in which they were run by C11Tester
(i.e., the "execution order"), which does not necessarily align with the "order"
of the values observed (i.e., the modification order or the reads-from
relation).
The following list describes each of the columns in the execution trace output:
* \#: The sequence number within the execution. That is, sequence number "9"
- means the operation was the 9th operation executed by CDSChecker. Note that
+ means the operation was the 9th operation executed by C11Tester. Note that
this represents the execution order, not necessarily any other order (e.g.,
modification order or reads-from).
* Location: The memory location on which this operation is operating. This is
well-defined for atomic write/read/RMW, but other operations are subject to
- CDSChecker implementation details.
+ C11Tester implementation details.
* Value: For reads/writes/RMW, the value returned by the operation. Note that
for RMW, this is the value that is *read*, not the value that was *written*.
- For other operations, 'value' may have some CDSChecker-internal meaning, or
+ For other operations, 'value' may have some C11Tester-internal meaning, or
it may simply be a don't-care (such as `0xdeadbeef`).
* Rf: For reads, the sequence number of the operation from which it reads.
So for any thread i, we say CV[i] is the sequence number of the most recent
operation in thread i such that operation i happens-before this operation.
- Notably, thread 0 is reserved as a dummy thread for certain CDSChecker
+ Notably, thread 0 is reserved as a dummy thread for certain C11Tester
operations.
See the following example trace:
-<pre>
-------------------------------------------------------------------------------------
-# t Action type MO Location Value Rf CV
-------------------------------------------------------------------------------------
-1 1 thread start seq_cst 0x7f68ff11e7c0 0xdeadbeef ( 0, 1)
-2 1 init atomic relaxed 0x601068 0 ( 0, 2)
-3 1 init atomic relaxed 0x60106c 0 ( 0, 3)
-4 1 thread create seq_cst 0x7f68fe51c710 0x7f68fe51c6e0 ( 0, 4)
-5 2 thread start seq_cst 0x7f68ff11ebc0 0xdeadbeef ( 0, 4, 5)
-6 2 atomic read relaxed 0x60106c 0 3 ( 0, 4, 6)
-7 1 thread create seq_cst 0x7f68fe51c720 0x7f68fe51c6e0 ( 0, 7)
-8 3 thread start seq_cst 0x7f68ff11efc0 0xdeadbeef ( 0, 7, 0, 8)
-9 2 atomic write relaxed 0x601068 0 ( 0, 4, 9)
-10 3 atomic read relaxed 0x601068 0 2 ( 0, 7, 0, 10)
-11 2 thread finish seq_cst 0x7f68ff11ebc0 0xdeadbeef ( 0, 4, 11)
-12 3 atomic write relaxed 0x60106c 0x2a ( 0, 7, 0, 12)
-13 1 thread join seq_cst 0x7f68ff11ebc0 0x2 ( 0, 13, 11)
-14 3 thread finish seq_cst 0x7f68ff11efc0 0xdeadbeef ( 0, 7, 0, 14)
-15 1 thread join seq_cst 0x7f68ff11efc0 0x3 ( 0, 15, 11, 14)
-16 1 thread finish seq_cst 0x7f68ff11e7c0 0xdeadbeef ( 0, 16, 11, 14)
-HASH 4073708854
-------------------------------------------------------------------------------------
-</pre>
+ ------------------------------------------------------------------------------------
+ # t Action type MO Location Value Rf CV
+ ------------------------------------------------------------------------------------
+ 1 1 thread start seq_cst 0x7f68ff11e7c0 0xdeadbeef ( 0, 1)
+ 2 1 init atomic relaxed 0x601068 0 ( 0, 2)
+ 3 1 init atomic relaxed 0x60106c 0 ( 0, 3)
+ 4 1 thread create seq_cst 0x7f68fe51c710 0x7f68fe51c6e0 ( 0, 4)
+ 5 2 thread start seq_cst 0x7f68ff11ebc0 0xdeadbeef ( 0, 4, 5)
+ 6 2 atomic read relaxed 0x60106c 0 3 ( 0, 4, 6)
+ 7 1 thread create seq_cst 0x7f68fe51c720 0x7f68fe51c6e0 ( 0, 7)
+ 8 3 thread start seq_cst 0x7f68ff11efc0 0xdeadbeef ( 0, 7, 0, 8)
+ 9 2 atomic write relaxed 0x601068 0 ( 0, 4, 9)
+ 10 3 atomic read relaxed 0x601068 0 2 ( 0, 7, 0, 10)
+ 11 2 thread finish seq_cst 0x7f68ff11ebc0 0xdeadbeef ( 0, 4, 11)
+ 12 3 atomic write relaxed 0x60106c 0x2a ( 0, 7, 0, 12)
+ 13 1 thread join seq_cst 0x7f68ff11ebc0 0x2 ( 0, 13, 11)
+ 14 3 thread finish seq_cst 0x7f68ff11efc0 0xdeadbeef ( 0, 7, 0, 14)
+ 15 1 thread join seq_cst 0x7f68ff11efc0 0x3 ( 0, 15, 11, 14)
+ 16 1 thread finish seq_cst 0x7f68ff11e7c0 0xdeadbeef ( 0, 16, 11, 14)
+ HASH 4073708854
+ ------------------------------------------------------------------------------------
Now consider, for example, operation 10:
CV[0] = 0, CV[1] = 7, CV[2] = 0, CV[3] = 10
+End of Execution Summary
+------------------------
+
+C11Tester prints summary statistics at the end of each execution. These
+summaries are based off of a few different properties of an execution, which we
+will break down here:
+
+* A _buggy_ execution is an execution in which C11Tester has found a real
+ bug: a data race, a deadlock, or a failure of a user-provided assertion.
+ C11Tester will only report bugs in feasible executions.
+
+
+Other Notes and Pitfalls
+------------------------
+
+* Data races may be reported as multiple bugs, one for each byte-address of the
+ data race in question. See, for example, this run:
+
+ $ ./run.sh test/releaseseq.o
+ ...
+ Bug report: 4 bugs detected
+ [BUG] Data race detected @ address 0x601078:
+ Access 1: write in thread 2 @ clock 4
+ Access 2: read in thread 3 @ clock 9
+ [BUG] Data race detected @ address 0x601079:
+ Access 1: write in thread 2 @ clock 4
+ Access 2: read in thread 3 @ clock 9
+ [BUG] Data race detected @ address 0x60107a:
+ Access 1: write in thread 2 @ clock 4
+ Access 2: read in thread 3 @ clock 9
+ [BUG] Data race detected @ address 0x60107b:
+ Access 1: write in thread 2 @ clock 4
+ Access 2: read in thread 3 @ clock 9
-Other Notes
------------
-* Deadlock detection: CDSChecker can detect deadlocks. For instance, try the
- following test program.
+See Also
+--------
+
+The C11Tester project page:
+
+> <http://demsky.eecs.uci.edu/c11tester.html>
- > ./run.sh test/deadlock.o
+The C11Tester source and accompanying benchmarks on Gitweb:
- Deadlock detection currently detects when a thread is about to step into a
- deadlock, without actually including the final step in the trace. But you can
- examine the program to see the next step.
+> <http://plrg.eecs.uci.edu/git/?p=c11tester.git>
+>
+> <http://plrg.eecs.uci.edu/git/?p=c11llvm.git>
+>
+> <http://plrg.eecs.uci.edu/git/?p=c11concurrency-benchmarks.git>
-* CDSChecker has to speculatively explore many execution behaviors due to the
- relaxed memory model, and many of these turn out to be infeasible (that is,
- they cannot be legally produced by the memory model). CDSChecker discards
- these executions as soon as it identifies them (see the "Number of infeasible
- executions" statistic); however, the speculation can occasionally cause
- CDSChecker to hit unexpected parts of the unit test program (causing a
- division by 0, for instance). In such programs, you might consider running
- CDSChecker with the `-u num` option.
Contact
Please feel free to contact us for more information. Bug reports are welcome,
and we are happy to hear from our users. We are also very interested to know if
-CDSChecker catches bugs in your programs.
+C11Tester catches bugs in your programs.
+
+Contact Weiyu Luo at <weiyul7@uci.edu> or Brian Demsky at <bdemsky@uci.edu>.
+
+
+Copyright
+---------
+
+Copyright © 2013 and 2019 Regents of the University of California. All rights reserved.
+
+C11Tester is distributed under the GPL v2. See the LICENSE file for details.
+
+
+Acknowledgments
+---------------
+
+This material is based upon work supported by the National Science
+Foundation under Grant Numbers 1740210 and 1319786 and Google Research
+awards.
-Contact Brian Norris at <banorris@uci.edu> or Brian Demsky at <bdemsky@uci.edu>.
+Any opinions, findings, and conclusions or recommendations expressed in
+this material are those of the author(s) and do not necessarily reflect
+the views of the National Science Foundation.
References
projects / c11tester.git / blobdiff