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bugfix: Setting OMPI_MPI_THREAD_LEVEL to a value different than requested crashes #13211

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bugfix: Setting OMPI_MPI_THREAD_LEVEL to a value different than requested crashes #13211

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4 changes: 3 additions & 1 deletion ompi/mpi/c/init.c.in
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
* and Technology (RIST). All rights reserved.
* Copyright (c) 2024 Triad National Security, LLC. All rights
* reserved.
* Copyright (c) 2025 Advanced Micro Devices, Inc. All rights reserved.
* $COPYRIGHT$
*
* Additional copyrights may follow
Expand Down Expand Up @@ -46,7 +47,8 @@ PROTOTYPE INT init(INT_OUT argc, ARGV argv)

if (NULL != (env = getenv("OMPI_MPI_THREAD_LEVEL"))) {
required = atoi(env);
if (required < MPI_THREAD_SINGLE || required > MPI_THREAD_MULTIPLE) {
if (required != MPI_THREAD_SINGLE && required != MPI_THREAD_FUNNELED &&
required != MPI_THREAD_SERIALIZED && required != MPI_THREAD_MULTIPLE) {
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Just curious: what's the need for this? Doesn't MPI specify the relationship between all the MPI_THREAD_* values such that < SINGLE and > MULTIPLE is guaranteed to be invalid?

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@abouteiller abouteiller May 12, 2025 •
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In the new MPI ABI, values are still ordered but not consecutive, so users could use one of the invalid intermediate values.

https://github.com/mpi-forum/mpi-abi-stubs/blob/e89a80017a3fe9a05d903ced2564c6342d678165/mpi.h#L334

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Sigh. Ok.

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Actually, this is worth a comment for those of us who look at this code and wonder why it is this way (and to make sure someone doesn't mistakenly return it to <SINGLE || >MULTIPLE someday). Can you please add comments in these places and describe that checking each individual value is required because of ABI? Thanks.

required = MPI_THREAD_MULTIPLE;
}
}
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28 changes: 20 additions & 8 deletions ompi/mpi/c/init_thread.c.in
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@
* reserved.
* Copyright (c) 2024 Triad National Security, LLC. All rights
* reserved.
* Copyright (c) 2025 Advanced Micro Devices, Inc. All rights reserved.
* $COPYRIGHT$
*
* Additional copyrights may follow
Expand All @@ -40,21 +41,32 @@ PROTOTYPE ERROR_CLASS init_thread(INT_OUT argc, ARGV argv, INT required,
INT_OUT provided)
{
int err, safe_required = MPI_THREAD_SERIALIZED;
bool err_arg_required = false;
char *env;

ompi_hook_base_mpi_init_thread_top(argc, argv, required, provided);

/* Detect an incorrect thread support level, but dont report until we have the minimum
* infrastructure setup.
*/
if( (MPI_THREAD_SINGLE == required) || (MPI_THREAD_SERIALIZED == required) ||
(MPI_THREAD_FUNNELED == required) || (MPI_THREAD_MULTIPLE == required) ) {
err_arg_required = (required != MPI_THREAD_SINGLE && required != MPI_THREAD_FUNNELED &&
required != MPI_THREAD_SERIALIZED && required != MPI_THREAD_MULTIPLE);
if (!err_arg_required) {
safe_required = required;
}

if (NULL != (env = getenv("OMPI_MPI_THREAD_LEVEL"))) {
safe_required = atoi(env);
}
else {
safe_required = required;
/* check for environment overrides for required thread level. If
* there is, check to see that it is a valid/supported thread level.
* If valid, the environment variable always override the provided thread
* level (even if lower than argument `required`). A user program can
* check `provided != required` to check if `required` has been overruled.
*/
if (NULL != (env = getenv("OMPI_MPI_THREAD_LEVEL"))) {
int env_required = atoi(env);
err_arg_required |= (env_required != MPI_THREAD_SINGLE && env_required != MPI_THREAD_FUNNELED &&
env_required != MPI_THREAD_SERIALIZED && env_required != MPI_THREAD_MULTIPLE);
if (!err_arg_required) {
safe_required = env_required;
}
}

Expand All @@ -70,7 +82,7 @@ PROTOTYPE ERROR_CLASS init_thread(INT_OUT argc, ARGV argv, INT required,
err = ompi_mpi_init(0, NULL, safe_required, provided, false);
}

if( safe_required != required ) {
if (err_arg_required) {
/* Trigger the error handler for the incorrect argument. Keep it separate from the
* check on the ompi_mpi_init return and report a nice, meaningful error message to
* the user. */
Expand Down