src/java.base/linux/native/libnet/linux_close.c

rev 13795 : 8150460: (linux|bsd|aix)_close.c: file descriptor table may become large or may not work at all
Reviewed-by:

@@ -1,7 +1,7 @@
 /*
- * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Oracle designates this

@@ -21,10 +21,12 @@
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  */
 
+#include <assert.h>
+#include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <signal.h>
 #include <pthread.h>
 #include <sys/types.h>

@@ -57,14 +59,36 @@
  * Signal to unblock thread
  */
 static int sigWakeup = (__SIGRTMAX - 2);
 
 /*
- * The fd table and the number of file descriptors
- */
-static fdEntry_t *fdTable;
-static int fdCount;
+ * fdTable holds one entry per file descriptor, up to a certain
+ * maximum.
+ * Theoretically, the number of possible file descriptors can get
+ * large, though usually it does not. To save memory, we keep file
+ * descriptors with large numerical values in an overflow table. That
+ * table is organized as a two-dimensional sparse array, allocated
+ * on demand.
+ */
+
+static fdEntry_t* fdTable;
+/* Max. number of file descriptors in fdTable. */
+static const int fdTableMaxSize = 0x1000; /* 4K */
+/* Max. theoretical number of file descriptor on system. */
+static int fdLimit;
+/* Length of fdTable, in number of entries. */
+static int fdTableLen;
+
+/* Overflow table: organized as array of n slabs, each holding
+ *   64k entries.
+ */
+static fdEntry_t** fdOverflowTable;
+/* Number of slabs in the overflow table */
+static int fdOverflowTableLen;
+/* Number of entries in one slab */
+static const int fdOverflowTableSlabSize = 0x10000; /* 64k */
+pthread_mutex_t fdOverflowTableLock = PTHREAD_MUTEX_INITIALIZER;
 
 /*
  * Null signal handler
  */
 static void sig_wakeup(int sig) {

@@ -76,22 +100,43 @@
  */
 static void __attribute((constructor)) init() {
     struct rlimit nbr_files;
     sigset_t sigset;
     struct sigaction sa;
+    int i = 0;
 
-    /*
-     * Allocate table based on the maximum number of
-     * file descriptors.
-     */
+    /* Determine the maximum number of possible file descriptors. */
     getrlimit(RLIMIT_NOFILE, &nbr_files);
-    fdCount = nbr_files.rlim_max;
-    fdTable = (fdEntry_t *)calloc(fdCount, sizeof(fdEntry_t));
+    if (nbr_files.rlim_max != RLIM_INFINITY) {
+        fdLimit = nbr_files.rlim_max;
+    } else {
+        /* We just do not know. */
+        fdLimit = INT_MAX;
+    }
+
+    /* Allocate table for low value file descriptors. */
+    fdTableLen = fdLimit < fdTableMaxSize ? fdLimit : fdTableMaxSize;
+    fdTable = (fdEntry_t*) calloc(fdTableLen, sizeof(fdEntry_t));
     if (fdTable == NULL) {
         fprintf(stderr, "library initialization failed - "
                 "unable to allocate file descriptor table - out of memory");
         abort();
+    } else {
+        for (i = 0; i < fdTableLen; i ++) {
+            pthread_mutex_init(&fdTable[i].lock, NULL);
+        }
+    }
+
+    /* Allocate overflow table, if needed */
+    if (fdLimit > fdTableMaxSize) {
+        fdOverflowTableLen = ((fdLimit - fdTableMaxSize) / fdOverflowTableSlabSize) + 1;
+        fdOverflowTable = (fdEntry_t**) calloc(fdOverflowTableLen, sizeof(fdEntry_t*));
+        if (fdOverflowTable == NULL) {
+            fprintf(stderr, "library initialization failed - "
+                    "unable to allocate file descriptor overflow table - out of memory");
+            abort();
+        }
     }
 
     /*
      * Setup the signal handler
      */

@@ -104,19 +149,55 @@
     sigaddset(&sigset, sigWakeup);
     sigprocmask(SIG_UNBLOCK, &sigset, NULL);
 }
 
 /*
- * Return the fd table for this fd or NULL is fd out
- * of range.
+ * Return the fd table for this fd.
  */
 static inline fdEntry_t *getFdEntry(int fd)
 {
-    if (fd < 0 || fd >= fdCount) {
+    fdEntry_t* result = NULL;
+
+    if (fd < 0) {
         return NULL;
     }
-    return &fdTable[fd];
+
+    /* This should not happen. If it does, our assumption about
+     * max. fd value was wrong. */
+    assert(fd < fdLimit);
+
+    if (fd < fdTableMaxSize) {
+        assert(fd < fdTableLen);
+        result = fdTable + fd;
+    } else {
+        const int indexInOverflowTable = fd - fdTableMaxSize;
+        const int rootindex = indexInOverflowTable / fdOverflowTableSlabSize;
+        const int slabindex = indexInOverflowTable % fdOverflowTableSlabSize;
+        assert(rootindex < fdOverflowTableLen);
+        assert(slabindex < fdOverflowTableSlabSize);
+        pthread_mutex_lock(&fdOverflowTableLock);
+        if (fdOverflowTable[rootindex] == NULL) {
+            fdEntry_t* const newSlab =
+                (fdEntry_t*)calloc(fdOverflowTableSlabSize, sizeof(fdEntry_t));
+            if (newSlab == NULL) {
+                fprintf(stderr, "Unable to allocate file descriptor table - out of memory");
+                pthread_mutex_unlock(&fdOverflowTableLock);
+                abort();
+            } else {
+                int i;
+                for (i = 0; i < fdOverflowTableSlabSize; i ++) {
+                    pthread_mutex_init(&newSlab[i].lock, NULL);
+                }
+                fdOverflowTable[rootindex] = newSlab;
+            }
+        }
+        pthread_mutex_unlock(&fdOverflowTableLock);
+        result = fdOverflowTable[rootindex] + slabindex;
+    }
+
+    return result;
+
 }
 
 /*
  * Start a blocking operation :-
  *    Insert thread onto thread list for the fd.