This patch series demonstrates and fixes a bug that causes crashes with
OpenMP 'taskwait' directives in heavily multi-threaded scenarios.
TLDR: The early return from __kmpc_omp_taskwait_deps_51 missed the
synchronization mechanism in place for the late return.
Additional debug assertions check for the implied invariants of the code.
@jpeyton52 found the timing hole as this sequence of events:
>
> 1. THREAD 1: A regular task with dependences is created, call it T1
> 2. THREAD 1: Call into `__kmpc_omp_taskwait_deps_51()` and create a stack
based depnode (`NULL` task), call it T2 (stack)
> 3. THREAD 2: Steals task T1 and executes it getting to
`__kmp_release_deps()` region.
> 4. THREAD 1: During processing of dependences for T2 (stack) (within
`__kmp_check_deps()` region), a link is created T1 -> T2. This increases
T2's (stack) `nrefs` count.
> 5. THREAD 2: Iterates through the successors list: decrement the T2's
(stack) npredecessor count. BUT HASN'T YET `__kmp_node_deref()`-ed it.
> 6. THREAD 1: Now when finished with `__kmp_check_deps()`, it returns false
because npredecessor count is 0, but T2's (stack) `nrefs` count is 2 because
THREAD 2 still references it!
> 7. THREAD 1: Because `__kmp_check_deps()` returns false, early exit.
> _Now the stack based depnode is invalid, but THREAD 2 still references it._
>
> We've reached improper stack referencing behavior. Varied results/crashes/
asserts can occur if THREAD 1 comes back and recreates the exact same depnode
in the exact same stack address during the same time THREAD 2 calls
`__kmp_node_deref()`.
Summary:
Freestanding builds have `stddef.h` and `stdint.h` but not `stdlib.h`.
We don't actually use any `stdlib.h` definitions in the OpenMP headers,
and some definitions from this header are usable without the OpenMP
runtime (allocators) so we should be able to do this. This ignores the
include if possible, removing the implicit include would possibly break
some applications so it stays here.
The `openmp` runtime failed to build on LoP with LLVM18 on LoP due to
the addition of `-Wvla-cxx-extension` as
```
llvm-project/openmp/runtime/src/ompt-general.cpp:711:15: error: variable length arrays in C++ are a Clang extension [-Werror,-Wvla-cxx-extension]
711 | int tmp_ids[ids_size];
| ^~~~~~~~
llvm-project/openmp/runtime/src/ompt-general.cpp:711:15: note: function parameter 'ids_size' with unknown value cannot be used in a constant expression
llvm-project/openmp/runtime/src/ompt-general.cpp:704:65: note: declared here
704 | OMPT_API_ROUTINE int ompt_get_place_proc_ids(int place_num, int ids_size,
| ^
1 error generated.
```
This patch is to ignore the checking against this usage.
Add libgomp.1.dylib for MacOS and libgomp.so.1 for Linux
Linkers on Mac and Linux pick up versioned libgomp dynamic library
files. The existing softlinks (libgomp.dylib for MacOS and libgomp.so
for Linux) are insufficient. This helps alleviate the issue of mixing
libgomp and libomp at runtime.
This patch modifies the signature of the `__kmp_print_tdg_dot` function
in `kmp_tasking.cpp` to include the global thread ID (gtid) as an
argument. The gtid is now correctly passed to the function.
- Updated the function declaration to accept the gtid parameter.
- Modified all calls to `__kmp_print_tdg_dot` to pass the correct gtid
value.
This change addresses issues encountered when compiling with
`OMPX_TASKGRAPH` enabled. No functional changes are expected beyond
successful compilation.
On powerpc, physical_package_id may not be available. Currently, this
causes openmp to fall back to flat topology and various affinity tests
fail.
Fix this by parsing core_siblings_list to deterimine which cpus belong
to the same socket. This matches what the testing code does. The code to
parse the CPU list format thankfully already exists.
Fixes https://github.com/llvm/llvm-project/issues/111809.
For `libomp` on AIX, we build shared object `libomp.so` first and then
archive it into libomp.a. This patch changes to use SO version `1` and
name the shared object `libomp.so.1` so that it is consistent with the
naming of other shared objects in AIX libraries, e.g., `libc++.so.1` in
`libc++.a`. With this change, the change made in commit
bde51d9b0d473447ea12fb14924f14ea167eec85 to ensure only `libomp.a` is
published on AIX is no longer necessary and is removed.
For `libomp` on AIX, we build shared object `libomp.so` first and then
archive it into `libomp.a`. Due to a CMake for AIX problem, the install
step also tries to publish `libomp.so`. While we use a script to build
`libomp.a` out-of-tree for Clang and avoided the problem, this chokes
the in-tree build for Flang. The issue will be reported to CMake but
before a fixed CMake is available, this patch ensures only `libomp.a` is
published.
This patch adds support for pause resource with a new enumerator
omp_pause_stop_tool. The expected behavior of this enumerator is
* omp_pause_resource: not allowed
* omp_pause_resource_all: equivalent to omp_pause_hard
Start __kmp_invoke_microtask with PACBTI in order to identify the
function as a valid branch target. Before returning, SP is
authenticated.
Also add the BTI and PAC markers to z_Linux_asm.S.
With this patch, libomp.so can now be generated with DT_AARCH64_BTI_PLT
when built with -mbranch-protection=standard.
The implementation is based on the code available in compiler-rt.
This fixes several of those when building with MSVC on Windows:
```
[3625/7617] Building CXX object
projects\openmp\runtime\src\CMakeFiles\omp.dir\kmp_affinity.cpp.obj
C:\src\git\llvm-project\openmp\runtime\src\kmp_affinity.cpp(2637):
warning C4062: enumerator 'KMP_HW_UNKNOWN' in switch of enum 'kmp_hw_t'
is not handled
C:\src\git\llvm-project\openmp\runtime\src\kmp.h(628): note: see
declaration of 'kmp_hw_t'
```
* Separate wasi and emscripten as they have different constraints and
abilities
* Emscripten mimics Linux/POSIX by statically linking the musl runtime.
This allow nearly all KMP_OS_LINUX code paths to work correctly. There
are only a few places that need to be adjusted related to dynamic
linking (dl_open)
* Internally link openmp globals
* With CommonLinkage it is needed to emit them in an assembly file, now
they are defined and used within each compilation unit
* With ExternalLinkage they suffer from duplicate symbols during linking
for unnamed globals like reduction/critical
* Interestingly this aligns with the TODO comment above this code
On non-hyperthreaded machines, the thread id is not always explicit in
the /proc/cpuinfo file. This patch adds a check to ensure the thread ids
are put in.
These are Intel-specific changes for the CPUID leaf 31 method for
detecting machine topology.
* Cleanup known levels usage in x2apicid topology algorithm
Change to be a constant mask of all Intel topology type values.
* Take unknown ids into account when sorting them
If a hardware id is unknown, then put further down the hardware thread
list so it will take last priority when assigning to threads.
* Have sub ids printed out for hardware thread dump
* Add caches to topology
New` kmp_cache_ids_t` class helps create cache ids which are then put
into the topology table after regular topology type ids have been put
in.
* Allow empty masks in place list creation
Have enumeration information and place list generation take into account
that certain hardware threads may be lacking certain layers
* Allow different procs to have different number of topology levels
Accommodates possible situation where CPUID.1F has different depth for
different hardware threads. Each hardware thread has a topology
description which is just a small set of its topology levels. These
descriptions are tracked to see if the topology is uniform or not.
* Change regular ids with logical ids
Instead of keeping the original sub ids that the x2apicid topology
detection algorithm gives, change each id to its logical id which is a
number: [0, num_items - 1]. This makes inserting new layers into the
topology significantly simpler.
* Insert caches into topology
This change takes into account that most topologies are uniform and
therefore can use the quicker method of inserting caches as equivalent
layers into the topology.
The debug assert is meant to check that the index is a valid which means
the runtime needs to check against the size of the array instead of the
number of threads. A free()-ed thread put back in the thread pool may
index into anywhere inside the task team's available array from 0 to
tt_max_threads potentially.
Fixes: #94260
This change makes the runtime use new OMPT state and sync kinds
introduced in OpenMP 5.1 in place of the deprecated implicit state and
sync kinds. Events from implicit barriers use different enumerators for
workshare, parallel, and teams.
Use more specific values from `ompt_work_t` to allow the tool identify
the schedule of a worksharing-loop. With this patch, the runtime will
report the schedule chosen by the runtime rather than necessarily the
schedule literally requested by the clause.
E.g., for guided + just one iteration per thread, the runtime would
choose and report static.
Fixes issue #63904
Add support to the runtime for 6.0 spec features that allow num_threads
clause to take a list, and also make use of the strict modifier.
Provides new compiler interface functions for these features.
- The first hidden-helper-thread did not trigger thread-begin
- The "detaching" from a target-task when waiting for completion missed
to call task-switch
- Target tasks identified themself as explicit task
Co-authored-by: Kaloyan Ignatov <kaloyan.ignatov@rwth-aachen.de>
Summary:
The `add_llvm_library` interface handles installing the llvm libraries,
however we want to do our own handling. Otherwise, this will install
into the `./lib` location instead of the `./lib/<target>` one.
Update the folder titles for targets in the monorepository that have not
seen taken care of for some time. These are the folders that targets are
organized in Visual Studio and XCode
(`set_property(TARGET <target> PROPERTY FOLDER "<title>")`)
when using the respective CMake's IDE generator.
* Ensure that every target is in a folder
* Use a folder hierarchy with each LLVM subproject as a top-level folder
* Use consistent folder names between subprojects
* When using target-creating functions from AddLLVM.cmake, automatically
deduce the folder. This reduces the number of
`set_property`/`set_target_property`, but are still necessary when
`add_custom_target`, `add_executable`, `add_library`, etc. are used. A
LLVM_SUBPROJECT_TITLE definition is used for that in each subproject's
root CMakeLists.txt.
This reverts commit 098c6dfa8157681699a71fce9e3d94515e66311f.
This reverts commit 8c718a3a91df4ab68dc3f1ca3887ea730c9aed84.
This reverts commit 4fb02de9d490d0773441aa30124bb4d1272230d3.
Summary:
A previous patch moved the code here and accidentally overrwrote the
include path that the LSP interface used. This caused incorrect errors
when using clangd with the offload project. This patch removes the
unnecessary header and makes sure we include the correct folder.
AIX has the `/proc` filesystem where `/proc/<pid>/lwp/<tid>/lwpsinfo` has
the thread state in binary, similar to Linux's
`/proc/<pid>/task/<tid>/stat` where the state is in ASCII. However, the
definition of state info `R` in `lwpsinfo` is `runnable`. In Linux,
state `R` means the thread is `running`. Therefore, `lwpsinfo` is not
ideal for our purpose of getting the current load of the system. This
patch uses `perfstat_cpu()` in AIX system library `libperfstat.a` to
obtain the number of threads current running on logical CPUs.
Root cause: Segmentation fault is caused by null pointer dereference
inside the __kmpc_fork_call_if function at
https://github.com/llvm/llvm-project/blob/main/openmp/runtime/src/z_Linux_asm.S#L1186
. __kmpc_fork_call_if is missing case to handle argc=0 .
Fix: Added a check inside the __kmp_invoke_microtask function to handle
the case when argc is 0.
---------
Co-authored-by: Singh <chasingh@amd.com>
When a child process is forked with OpenMP already initialized, the
child process resets its affinity mask and sets proc-bind-var to false
so that the entire original affinity mask is used. This patch corrects
an issue with the affinity initialization code setting affinity to
compact instead of none for this special case of forked children.
The test trying to catch this only testing explicit setting of
KMP_AFFINITY=none. Add test run for no KMP_AFFINITY setting.
Fixes: #91098
