Add multithreading helpers

Add an abstraction for mutexts and threads
that handles both pthread api and native win32 api

Signed-off-by: Ronnie Sahlberg <ronniesahlberg@gmail.com>

include/iscsi-multithreading.h

@@ -0,0 +1,73 @@
+/* -*-  mode:c; tab-width:8; c-basic-offset:8; indent-tabs-mode:nil;  -*- */
+/*
+   Copyright (C) 2025 by Ronnie Sahlberg <ronniesahlberg@gmail.com>
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU Lesser General Public License as published by
+   the Free Software Foundation; either version 2.1 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public License
+   along with this program; if not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef _LIBISCSI_MULTITHREADING_H_
+#define _LIBISCSI_MULTITHREADING_H_
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifdef HAVE_MULTITHREADING
+
+#ifdef WIN32
+typedef HANDLE libiscsi_thread_t;
+typedef HANDLE libiscsi_mutex_t;
+typedef HANDLE libiscsi_sem_t;
+typedef DWORD iscsi_tid_t;
+#elif defined(HAVE_PTHREAD)
+#include <pthread.h>
+typedef pthread_t libiscsi_thread_t;
+typedef pthread_mutex_t libiscsi_mutex_t;
+
+#if defined(__APPLE__) && defined(HAVE_DISPATCH_DISPATCH_H)
+#include <dispatch/dispatch.h>
+typedef dispatch_semaphore_t libiscsi_sem_t;
+#else
+#include <semaphore.h>
+typedef sem_t libiscsi_sem_t;
+#endif
+#ifdef HAVE_PTHREAD_THREADID_NP
+typedef uint64_t iscsi_tid_t;
+#else
+typedef pid_t iscsi_tid_t;
+#endif
+#endif /* HAVE_PTHREAD */
+
+iscsi_tid_t iscsi_mt_get_tid(void);
+int iscsi_mt_mutex_init(libiscsi_mutex_t *mutex);
+int iscsi_mt_mutex_destroy(libiscsi_mutex_t *mutex);
+int iscsi_mt_mutex_lock(libiscsi_mutex_t *mutex);
+int iscsi_mt_mutex_unlock(libiscsi_mutex_t *mutex);
+
+int iscsi_mt_sem_init(libiscsi_sem_t *sem, int value);
+int iscsi_mt_sem_destroy(libiscsi_sem_t *sem);
+int iscsi_mt_sem_post(libiscsi_sem_t *sem);
+int iscsi_mt_sem_wait(libiscsi_sem_t *sem);
+
+#endif /* HAVE_MULTITHREADING */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* !_LIBISCSI_MULTITHREADING_H_ */

include/iscsi-private.h

@@ -28,6 +28,39 @@
 
 #include "iscsi.h"
 
+#ifdef HAVE_MULTITHREADING
+#ifdef HAVE_STDATOMIC_H
+#include <stdatomic.h>
+#define ATOMIC_INC(rpc, x) \
+        atomic_fetch_add_explicit(&x, 1, memory_order_relaxed)
+#define ATOMIC_DEC(rpc, x) \
+        atomic_fetch_sub_explicit(&x, 1, memory_order_relaxed)
+#else /* HAVE_STDATOMIC_H */
+#define ATOMIC_INC(rpc, x)                              \
+        if (rpc->multithreading_enabled) {              \
+                nfs_mt_mutex_lock(&rpc->atomic_int_mutex);     \
+        }                                               \
+	x++;                                            \
+        if (rpc->multithreading_enabled) {              \
+                nfs_mt_mutex_unlock(&rpc->atomic_int_mutex);   \
+        }
+#define ATOMIC_DEC(rpc, x)                              \
+        if (rpc->multithreading_enabled) {              \
+                nfs_mt_mutex_lock(&rpc->atomic_int_mutex);     \
+        }                                               \
+	x--;                                            \
+        if (rpc->multithreading_enabled) {              \
+                nfs_mt_mutex_unlock(&rpc->atomic_int_mutex);   \
+        }
+#endif /* HAVE_STDATOMIC_H */
+#else /* HAVE_MULTITHREADING */
+/* no multithreading support, no need to protect the increment */
+#define ATOMIC_INC(rpc, x) x++
+#define ATOMIC_DEC(rpc, x) x--
+#endif /* HAVE_MULTITHREADING */
+
+#include "iscsi-multithreading.h"
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -184,6 +217,19 @@ struct iscsi_context {
 	int no_ua_on_reconnect;
 	void (*fd_dup_cb)(struct iscsi_context *iscsi, void *opaque);
 	void *fd_dup_opaque;
+
+#ifdef HAVE_MULTITHREADING
+        int multithreading_enabled;
+        libiscsi_mutex_t iscsi_mutex;
+        libiscsi_thread_t service_thread;
+        int poll_timeout;
+        //libnfs_mutex_t nfs4_open_counter_mutex;
+        //libnfs_mutex_t nfs4_open_call_mutex;
+        //struct nfs_thread_context *thread_ctx;
+#ifndef HAVE_STDATOMIC_H
+        libiscsi_mutex_t atomic_int_mutex;
+#endif /* HAVE_STDATOMIC_H */
+#endif /* HAVE_MULTITHREADING */
 };
 
 #define ISCSI_PDU_IMMEDIATE		       0x40