X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=ipc.c;h=85013a636cb3a7f634d190d9044808454274efd8;hp=6a0f00b5a2373b0d04df8527ce4d4f3daa933a7d;hb=23dd2200dd4fc74025ae87f5c2127f3b0ff71e9b;hpb=6668ac4a8c7f2a92efb9e6d405d954beff77d230

diff --git a/ipc.c b/ipc.c
index 6a0f00b5..85013a63 100644
--- a/ipc.c
+++ b/ipc.c
@@ -1,14 +1,14 @@
-/*
- * Copyright (C) 2006-2010 Andre Noll <maan@systemlinux.org>
- *
- * Licensed under the GPL v2. For licencing details see COPYING.
- */
+/* Copyright (C) 2006 Andre Noll <maan@tuebingen.mpg.de>, see file COPYING. */
 
 /** \file ipc.c Inter-process communication and shared memory helpers. */
 
 #include "para.h"
 #include "error.h"
 #include "ipc.h"
+#include <sys/types.h>
+#include <sys/param.h>
+#include <sys/sysctl.h>
+
 #include <sys/ipc.h>
 #include <sys/shm.h>
 #include <sys/sem.h>
@@ -64,7 +64,7 @@ static void para_semop(int id, struct sembuf *sops, int num)
  *
  * This function either succeeds or aborts.
  *
- * \sa semop(2), struct misc_meta_data.
+ * \sa semop(2), struct \ref misc_meta_data.
  */
 void mutex_lock(int id)
 {
@@ -90,7 +90,7 @@ void mutex_lock(int id)
  *
  * This function either succeeds or aborts.
  *
- * \sa semop(2), struct misc_meta_data.
+ * \sa semop(2), struct \ref misc_meta_data.
  */
 void mutex_unlock(int id)
 {
@@ -157,6 +157,27 @@ int shm_attach(int id, enum shm_attach_mode mode, void **result)
 	return *result == (void *) -1? -ERRNO_TO_PARA_ERROR(errno) : 1;
 }
 
+/**
+ * Get the size of a shared memory segment.
+ *
+ * \param id The shared memory segment identifier.
+ * \param result Size in bytes is returned here, zero on errors.
+ *
+ * \return Standard.
+ *
+ * \sa shmctl(2).
+ */
+int shm_size(int id, size_t *result)
+{
+	struct shmid_ds ds; /* data structure */
+
+	*result = 0;
+	if (shmctl(id, IPC_STAT, &ds) < 0)
+		return -ERRNO_TO_PARA_ERROR(errno);
+	*result = ds.shm_segsz;
+	return 1;
+}
+
 /**
  * Detach a shared memory segment.
  *
@@ -171,3 +192,55 @@ int shm_detach(void *addr)
 	int ret = shmdt(addr);
 	return ret < 0? -ERRNO_TO_PARA_ERROR(errno) : 1;
 }
+
+# if defined __FreeBSD__ || defined __NetBSD__
+# 	define SYSCTL_SHMMAX_VARIABLE "kern.ipc.shmmax"
+# elif defined __APPLE__
+# 	define SYSCTL_SHMMAX_VARIABLE "kern.sysv.shmmax"
+# else
+#	undef SYSCTL_SHMMAX_VARIABLE
+# endif
+
+/**
+ * Get the maximal size of a shared memory area.
+ *
+ * The value is only computed once when the function is called for the first
+ * time.  Subsequent calls return the number which was computed during the
+ * first call.
+ *
+ * \return A number suitable as an argument to \ref shm_new().
+ */
+size_t shm_get_shmmax(void)
+{
+	static size_t shmmax;
+
+	if (shmmax > 0) /* only dance once */
+		return shmmax;
+#ifdef __linux__ /* get it from proc fs */
+	{
+		int fd = open("/proc/sys/kernel/shmmax", O_RDONLY);
+		if (fd >= 0) {
+			char buf[100] = "";
+			int ret = read(fd, buf, sizeof(buf) - 1);
+			if (ret > 0) {
+				buf[ret] = '\0';
+				shmmax = strtoul(buf, NULL, 10);
+			}
+			close(fd);
+		}
+	}
+#elif defined SYSCTL_SHMMAX_VARIABLE
+	{
+		size_t len = sizeof(shmmax);
+		sysctlbyname(SYSCTL_SHMMAX_VARIABLE, &shmmax, &len, NULL, 0);
+	}
+#elif defined SHMMAX
+	shmmax = SHMMAX;
+#endif
+	if (shmmax == 0) {
+		PARA_WARNING_LOG("unable to determine shmmax\n");
+		shmmax = 65535; /* last resort */
+	}
+	PARA_INFO_LOG("shmmax: %zu\n", shmmax);
+	return shmmax;
+}