fix: deadlock in exec_blas_async after fork

driver/others/blas_server.c

@@ -637,9 +637,7 @@ int exec_blas_async(BLASLONG pos, blas_queue_t *queue){
 
 #ifdef SMP_SERVER
   // Handle lazy re-init of the thread-pool after a POSIX fork
-  LOCK_COMMAND(&server_lock);
   if (unlikely(blas_server_avail == 0)) blas_thread_init();
-  UNLOCK_COMMAND(&server_lock);
 #endif
   BLASLONG i = 0;
   blas_queue_t *current = queue;

utest/CMakeLists.txt

@@ -101,6 +101,7 @@ if (NOT USE_OPENMP)
 set(OpenBLAS_utest_src
   ${OpenBLAS_utest_src}
   test_fork.c
+  test_post_fork_async.c
   )
 endif()
 set(OpenBLAS_utest_src

utest/Makefile

@@ -45,7 +45,7 @@ endif
 # 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
+OBJS += test_fork.o test_post_fork_async.o
 endif
 OBJS += test_post_fork.o
 endif

utest/test_post_fork_async.c

@@ -0,0 +1,94 @@
+/*****************************************************************************
+Copyright (c) 2011-2025, The OpenBLAS Project
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   1. Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+   2. Redistributions in binary form must reproduce the above copyright
+      notice, this list of conditions and the following disclaimer in
+      the documentation and/or other materials provided with the
+      distribution.
+   3. Neither the name of the OpenBLAS project nor the names of
+      its contributors may be used to endorse or promote products
+      derived from this software without specific prior written
+      permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+**********************************************************************************/
+
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <errno.h>
+#include <cblas.h>
+#include "openblas_utest.h"
+
+static void* xmalloc(size_t n)
+{
+    void* tmp;
+    tmp = calloc(1, n);
+    if (tmp == NULL) {
+        fprintf(stderr, "Failed to allocate memory for the testcase.\n");
+        exit(1);
+    } else {
+        return tmp;
+    }
+}
+
+CTEST(fork, safety_after_fork_async)
+{
+#ifdef __UCLIBC__
+#if !defined __UCLIBC_HAS_STUBS__ && !defined __ARCH_USE_MMU__
+exit(0);
+#endif
+#endif
+#ifndef BUILD_DOUBLE
+exit(0);
+#else
+    blasint n = 200;
+    blasint info;
+    blasint i;
+
+    blasint *ipiv;
+    double *arr;
+
+    pid_t fork_pid;
+
+    arr = xmalloc(sizeof(*arr) * n * n);
+    ipiv = xmalloc(sizeof(*ipiv) * n);
+
+    // array is an identity matrix
+    for (i = 0; i < n*n; i += n + 1) {
+        arr[i] = 1.0;
+    }
+
+    fork_pid = fork();
+    if (fork_pid == -1) {
+        perror("fork");
+        CTEST_ERR("Failed to fork process.");
+    } else if (fork_pid == 0) {
+      exit(0);
+    } else {
+        // Wait for the child to finish and check the exit code.
+        int child_status = 0;
+        pid_t wait_pid = wait(&child_status);
+        ASSERT_EQUAL(wait_pid, fork_pid);
+        ASSERT_EQUAL(0, WEXITSTATUS (child_status));
+    }
+    BLASFUNC(dgetrf)(&n, &n, arr, &n, ipiv, &info);
+#endif
+}