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The plugins in these subdirectories are intended as simple examples.
To try PLUGIN, do: cd PLUGIN; make check
After killing process, try: ./
For an organized way to explore the plugins, we recommend following the
"SELF-GUIDED TOUR". (See below.)
GNU glibc uses libc-low-level-lock to manage thread safety, since multiple
threads could call printf(), malloc(), etc., at the same time. If the
target program is being checkpointed when glibc holds this lock in the
middle of printing or allocating, and if dmtcp_process_event() tries to
call printf(), malloc(), etc., then deadlock will ensue. A similar issue
can affect the C++ runtime library.
If this issue affects you, then:
a. implement your own calls to read()/write() and your own memory allocator; or
b. ensure with other logic that your plugin and target application do not
simultaneously attempt to print, allocate memory, etc.
example: how to react to special events (init, ckpt, resume, restart, ...)
sleep1: wrapper around sleep() in program ../../test/dmtcp1
(displays seconds and microseconds, before and after sleep())
sleep2: second wrapper around sleep() in program ../../test/dmtcp1
'make check' invokes the sleep1 and sleep2 wrappers simultaneously.
example-db: uses the database service of DMTCP. At checkpoint or
restart time, each process can install a key-value pair, and then
optionally query a value for a given key.
applic-initiated-ckpt: demonstrates how an application can initiate
a checkpoint of itself.
For a self-guided tour of plugins, try the commands below. Be sure to stop
during the tour and read some of the .c files. We believe you will be
impressed by how few lines of code can express so much flexibility
for checkpointing:
cd sleep1
make clean
make -n
make -n check
make check
cd ../sleep2
make clean
make -n check
make check
cd ../applic-initiated-ckpt
./applic # Notice that there is no DMTCP when running in this mode.
../../../bin/dmtcp_launch ./applic
../../../bin/dmtcp_restart ckpt_applic_*.dmtcp