From ef015a68303cb5b7700e852015db91a760daa1e0 Mon Sep 17 00:00:00 2001
From: Ivan K <krylov.r00t@gmail.com>
Date: Sat, 10 Jun 2023 20:35:59 +0300
Subject: [PATCH 1/2] blas_thread_shutdown: release OpenMP resources too

OpenMP 5.0 introduced the function omp_pause_resource_all that instructs
the runtime to "relinquish resources used by OpenMP on all devices". In
practice, these resources include the locks that would otherwise trip up
the runtime after a fork(). Releasing these resources in a function
called by pthread_atfork() makes it possible for the child process to
continue functioning after the runtime automatically re-acquires its
resources.

Thread safety: blas_thread_shutdown doesn't check whether there are
other BLAS operations running in parallel, so this isn't any less safe
than before with respect to OpenBLAS function calls. On the other hand,
if there are other OpenMP operations in progress, asking the runtime to
pause may result in unspecified behaviour. A hard pause is allowed to
deallocate threadprivate variables too.
---
 driver/others/blas_server_omp.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/driver/others/blas_server_omp.c b/driver/others/blas_server_omp.c
index 2e0c0f38c..08bf2170f 100644
--- a/driver/others/blas_server_omp.c
+++ b/driver/others/blas_server_omp.c
@@ -48,6 +48,7 @@
 
 #else
 
+#include <omp.h>
 #ifndef likely
 #ifdef __GNUC__
 #define likely(x) __builtin_expect(!!(x), 1)
@@ -147,6 +148,9 @@ int BLASFUNC(blas_thread_shutdown)(void){
       }
     }
   }
+#if defined(_OPENMP) && _OPENMP >= 201811
+  omp_pause_resource_all(omp_pause_hard);
+#endif
 
   return 0;
 }

From 645eabe67f1fc01da855647f63e1b1576b495bb3 Mon Sep 17 00:00:00 2001
From: Ivan K <krylov.r00t@gmail.com>
Date: Sat, 10 Jun 2023 21:20:58 +0300
Subject: [PATCH 2/2] utest: test fork safety on OpenMP >= 5

In addition to testing fork safety on non-OpenMP builds, test it on
OpenMP >= 5.0, where we get the ability to release the locks at fork()
time.
---
 utest/Makefile    | 5 +----
 utest/test_fork.c | 2 +-
 2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/utest/Makefile b/utest/Makefile
index f99035440..eecd9d199 100644
--- a/utest/Makefile
+++ b/utest/Makefile
@@ -26,10 +26,7 @@ endif
 #this does not work with OpenMP nor with native Windows or Android threads
 # FIXME TBD if this works on OSX, SunOS, POWER and zarch
 ifeq ($(OSNAME), $(filter $(OSNAME),Linux CYGWIN_NT))
-ifneq ($(USE_OPENMP), 1)
-OBJS += test_fork.o
-endif
-OBJS += test_post_fork.o
+OBJS += test_fork.o test_post_fork.o
 endif
 
 ifeq ($(C_COMPILER), PGI)
diff --git a/utest/test_fork.c b/utest/test_fork.c
index bd531e7fb..b1cd380e6 100644
--- a/utest/test_fork.c
+++ b/utest/test_fork.c
@@ -64,7 +64,7 @@ static void check_dgemm(double *a, double *b, double *result, double *expected,
 
 CTEST(fork, safety)
 {
-#ifndef BUILD_DOUBLE
+#if !defined(BUILD_DOUBLE) || (defined(_OPENMP) && _OPENMP < 201811)
 exit(0);
 #else
     blasint n = 1000;