eal: check if primary process is alive

This patch adds a new function to the EAL API:
int rte_eal_primary_proc_alive(const char *path);

The function indicates if a primary process is alive right now.
This functionality is implemented by testing for a write-
lock on the config file, and the function tests for a lock.

The use case for this functionality is that a secondary
process can wait until a primary process starts by polling
the function and waiting. When the primary is running, the
secondary continues to poll to detect if the primary process
has quit unexpectedly, the secondary process can detect this.

Signed-off-by: Harry van Haaren <harry.van.haaren@intel.com>
Acked-by: Maryam Tahhan <maryam.tahhan@intel.com>

doc/guides/rel_notes/release_16_04.rst

@@ -35,6 +35,13 @@ This section should contain new features added in this release. Sample format:
 
   Refer to the previous release notes for examples.
 
+* **Added function to check primary process state.**
+
+  A new function ``rte_eal_primary_proc_alive()`` has been added
+  to allow the user to detect if a primary process is running.
+  Use cases for this feature include fault detection, and monitoring
+  using secondary processes.
+
 * **Enabled bulk allocation of mbufs.**
 
   A new function ``rte_pktmbuf_alloc_bulk()`` has been added to allow the user

lib/librte_eal/bsdapp/eal/Makefile

@@ -79,6 +79,7 @@ SRCS-$(CONFIG_RTE_EXEC_ENV_BSDAPP) += eal_common_devargs.c
 SRCS-$(CONFIG_RTE_EXEC_ENV_BSDAPP) += eal_common_dev.c
 SRCS-$(CONFIG_RTE_EXEC_ENV_BSDAPP) += eal_common_options.c
 SRCS-$(CONFIG_RTE_EXEC_ENV_BSDAPP) += eal_common_thread.c
+SRCS-$(CONFIG_RTE_EXEC_ENV_BSDAPP) += eal_common_proc.c
 SRCS-$(CONFIG_RTE_EXEC_ENV_BSDAPP) += rte_malloc.c
 SRCS-$(CONFIG_RTE_EXEC_ENV_BSDAPP) += malloc_elem.c
 SRCS-$(CONFIG_RTE_EXEC_ENV_BSDAPP) += malloc_heap.c

lib/librte_eal/bsdapp/eal/rte_eal_version.map

@@ -148,5 +148,6 @@ DPDK_16.04 {
 	rte_eal_pci_ioport_write;
 	rte_eal_pci_map_device;
 	rte_eal_pci_unmap_device;
+	rte_eal_primary_proc_alive;
 
 } DPDK_2.2;

lib/librte_eal/common/eal_common_proc.c

@@ -0,0 +1,61 @@
+/*-
+ *   BSD LICENSE
+ *
+ *   Copyright(c) 2016 Intel Corporation. All rights reserved.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following conditions
+ *   are met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * 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.
+ *     * Neither the name of Intel Corporation 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 <stdio.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <rte_eal.h>
+
+#include "eal_filesystem.h"
+#include "eal_internal_cfg.h"
+
+int
+rte_eal_primary_proc_alive(const char *config_file_path)
+{
+	int config_fd;
+
+	if (config_file_path)
+		config_fd = open(config_file_path, O_RDONLY);
+	else {
+		char default_path[PATH_MAX+1];
+		snprintf(default_path, PATH_MAX, RUNTIME_CONFIG_FMT,
+			 default_config_dir, "rte");
+		config_fd = open(default_path, O_RDONLY);
+	}
+	if (config_fd < 0)
+		return 0;
+
+	int ret = lockf(config_fd, F_TEST, 0);
+	close(config_fd);
+
+	return !!ret;
+}

lib/librte_eal/common/include/rte_eal.h

@@ -1,7 +1,7 @@
 /*-
  *   BSD LICENSE
  *
- *   Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
+ *   Copyright(c) 2010-2016 Intel Corporation. All rights reserved.
  *   All rights reserved.
  *
  *   Redistribution and use in source and binary forms, with or without
@@ -156,6 +156,24 @@ int rte_eal_iopl_init(void);
  *   - On failure, a negative error value.
  */
 int rte_eal_init(int argc, char **argv);
+
+/**
+ * Check if a primary process is currently alive
+ *
+ * This function returns true when a primary process is currently
+ * active.
+ *
+ * @param config_file_path
+ *   The config_file_path argument provided should point at the location
+ *   that the primary process will create its config file. If NULL, the default
+ *   config file path is used.
+ *
+ * @return
+ *  - If alive, returns 1.
+ *  - If dead, returns 0.
+ */
+int rte_eal_primary_proc_alive(const char *config_file_path);
+
 /**
  * Usage function typedef used by the application usage function.
  *

lib/librte_eal/linuxapp/eal/Makefile

@@ -1,6 +1,6 @@
 #   BSD LICENSE
 #
-#   Copyright(c) 2010-2015 Intel Corporation. All rights reserved.
+#   Copyright(c) 2010-2016 Intel Corporation. All rights reserved.
 #   All rights reserved.
 #
 #   Redistribution and use in source and binary forms, with or without
@@ -89,6 +89,7 @@ SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += eal_common_devargs.c
 SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += eal_common_dev.c
 SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += eal_common_options.c
 SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += eal_common_thread.c
+SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += eal_common_proc.c
 SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += rte_malloc.c
 SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += malloc_elem.c
 SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += malloc_heap.c

lib/librte_eal/linuxapp/eal/rte_eal_version.map

@@ -151,5 +151,6 @@ DPDK_16.04 {
 	rte_eal_pci_ioport_write;
 	rte_eal_pci_map_device;
 	rte_eal_pci_unmap_device;
+	rte_eal_primary_proc_alive;
 
 } DPDK_2.2;