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Bug#52261: 64 bit atomic operations do not work on Solaris i386
gcc in debug compilation
One of the various problems was that the source operand to
CMPXCHG8b was marked as a input/output operand, causing GCC
to use the EBX register as the destination register for the
CMPXCHG8b instruction. This could lead to crashes as the EBX
register is also implicitly used by the instruction, causing
the value to be potentially garbaged and a protection fault
once the value is used to access a position in memory.
Another problem was the lack of proper clobbers for the atomic
operations and, also, a discrepancy between the implementations
for the Compare and Set operation. The specific problems are
described and fixed by Kristian Nielsen patches:
Patch: 1
Fix bugs in my_atomic_cas*(val,cmp,new) that *cmp is accessed
after CAS succeds.
In the gcc builtin implementation, problem was that *cmp was
read again after atomic CAS to check if old *val == *cmp;
this fails if CAS is successful and another thread modifies
*cmp in-between.
In the x86-gcc implementation, problem was that *cmp was set
also in the case of successful CAS; this means there is a
window where it can clobber a value written by another thread
after successful CAS.
Patch 2:
Add a GCC asm "memory" clobber to primitives that imply a
memory barrier.
This signifies to GCC that any potentially aliased memory
must be flushed before the operation, and re-read after the
operation, so that read or modification in other threads of
such memory values will work as intended.
In effect, it makes these primitives work as memory barriers
for the compiler as well as the CPU. This is better and more
correct than adding "volatile" to variables.
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|---|---|---|
| .. | ||
| examples | ||
| mysys | ||
| mytap | ||
| Makefile.am | ||
| README.txt | ||
| unit.pl | ||
Unit tests directory structure
------------------------------
This is the current structure of the unit tests. More directories
will be added over time.
mytap Source for the MyTAP library
mysys Tests for mysys components
bitmap-t.c Unit test for MY_BITMAP
base64-t.c Unit test for base64 encoding functions
examples Example unit tests.
core-t.c Example of raising a signal in the middle of the test
THIS TEST WILL STOP ALL FURTHER TESTING!
simple-t.c Example of a standard TAP unit test
skip-t.c Example where some test points are skipped
skip_all-t.c Example of a test where the entire test is skipped
todo-t.c Example where test contain test points that are TODO
no_plan-t.c Example of a test with no plan (avoid this)
Executing unit tests
--------------------
To make and execute all unit tests in the directory:
make test
Observe that the tests in the examples/ directory are just various
examples of tests and are not expected to pass.
Adding unit tests
-----------------
Add a file with a name of the format "foo-t.c" to the appropriate
directory and add the following to the Makefile.am in that directory
(where ... denotes stuff already there):
noinst_PROGRAMS = ... foo-t
Note, it's important to have "-t" at the end of the filename, otherwise the
test won't be executed by 'make test' !
Documentation
-------------
The generated documentation is temporarily placed at:
http://www.kindahl.net/mytap/doc/
I will move it to a better place once I figure out where and how.