In code like this from include/parallel/workstealing.h (libstdc++ parallel
mode)
// After reaching this point, a thread's job list is empty.
if (iam_working)
{
//This thread no longer has work.
#pragma omp atomic
busy--;
iam_working = false;
}
the instruction belonging to the omp atomic pragma is skipped by the compiler,
i. e. busy is _not_ decremented.
Adding pragma omp flush before and after does not help either. Replacing the
two lines by "__sync_fetch_and_add(&busy, -1);" makes the program work
correctly.
Unfortunately, I have not yet succeeded in constructing a test case simpler
than calling e. g. parallel for_each, and checking the result. The problem
could maybe be caused by incorrect inlining.
--
Summary: [libgomp/parallel mode] pragma omp atomic broken
Product: gcc
Version: 4.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libgomp
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: singler at ira dot uka dot de
GCC build triplet: x86_64-unknown-linux-gnu
GCC host triplet: x86_64-unknown-linux-gnu
GCC target triplet: x86_64-unknown-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33894
