Initial commit of vpp code.v1.0.0

Change-Id: Ib246f1fbfce93274020ee93ce461e3d8bd8b9f17
Signed-off-by: Ed Warnicke <eaw@cisco.com>

1 files changed, 1045 insertions, 0 deletions

diff --git a/svm/svm.c b/svm/svm.c
new file mode 100644
index 00000000000..c629f932008
--- /dev/null
+++ b/svm/svm.c
@@ -0,0 +1,1045 @@
+/* 
+ *------------------------------------------------------------------
+ * svm.c - shared VM allocation, mmap(...MAP_FIXED...) 
+ * library
+ *
+ * Copyright (c) 2009 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *------------------------------------------------------------------
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <netinet/in.h>
+#include <signal.h>
+#include <pthread.h>
+#include <unistd.h>
+#include <time.h>
+#include <fcntl.h>
+#include <string.h>
+#include <vppinfra/clib.h>
+#include <vppinfra/vec.h>
+#include <vppinfra/hash.h>
+#include <vppinfra/bitmap.h>
+#include <vppinfra/fifo.h>
+#include <vppinfra/time.h>
+#include <vppinfra/mheap.h>
+#include <vppinfra/heap.h>
+#include <vppinfra/pool.h>
+#include <vppinfra/format.h>
+
+#include "svm.h"
+
+static svm_region_t *root_rp;
+static int root_rp_refcount;
+
+#define MAXLOCK 2
+static pthread_mutex_t *mutexes_held [MAXLOCK];
+static int nheld;
+
+svm_region_t *svm_get_root_rp (void)
+{
+    return root_rp;
+}
+
+#define MUTEX_DEBUG
+
+static void region_lock(svm_region_t *rp, int tag)
+{
+    pthread_mutex_lock(&rp->mutex);
+#ifdef MUTEX_DEBUG
+    rp->mutex_owner_pid = getpid();
+    rp->mutex_owner_tag = tag;
+#endif    
+    ASSERT(nheld < MAXLOCK);
+    /* 
+     * Keep score of held mutexes so we can try to exit
+     * cleanly if the world comes to an end at the worst possible
+     * moment
+     */
+    mutexes_held [nheld++] = &rp->mutex;
+}
+
+static void region_unlock(svm_region_t *rp)
+{
+    int i,j;
+#ifdef MUTEX_DEBUG
+    rp->mutex_owner_pid = 0;
+    rp->mutex_owner_tag = 0;
+#endif    
+
+    for (i = nheld-1; i >= 0; i--) {
+        if (mutexes_held[i] == &rp->mutex) {
+            for (j = i; j < MAXLOCK-1; j++)
+                mutexes_held[j] = mutexes_held[j+1];
+            nheld--;
+            goto found;
+        }
+    }
+    ASSERT(0);
+
+found:
+    CLIB_MEMORY_BARRIER();
+    pthread_mutex_unlock(&rp->mutex);
+}
+
+
+static u8 * format_svm_flags (u8 * s, va_list * args)
+{
+    uword f = va_arg (*args, uword);
+
+    if (f & SVM_FLAGS_MHEAP)
+        s = format (s, "MHEAP ");
+    if (f & SVM_FLAGS_FILE)
+        s = format (s, "FILE ");
+    if (f & SVM_FLAGS_NODATA)
+        s = format (s, "NODATA ");
+    if (f & SVM_FLAGS_NEED_DATA_INIT)
+        s = format (s, "INIT ");
+        
+    return (s);
+}
+
+static u8 * format_svm_size (u8 * s, va_list * args)
+{
+    uword size = va_arg (*args, uword);
+
+    if (size >= (1>>20)) {
+        s = format (s, "(%d mb)", size >> 20);
+    } else if (size >= (1>>10)) {
+        s = format (s, "(%d kb)", size >> 10);
+    } else {
+        s = format (s, "(%d bytes)", size);
+    }
+    return (s);
+}
+
+u8 * format_svm_region (u8 * s, va_list * args)
+{
+    svm_region_t *rp = va_arg (*args, svm_region_t *);
+    int verbose = va_arg (*args, int);
+    int i;
+    uword lo, hi;
+
+    s = format (s, "%s: base va 0x%x size 0x%x %U\n",
+                rp->region_name, rp->virtual_base,
+                rp->virtual_size, format_svm_size, rp->virtual_size);
+    s = format (s, "  user_ctx 0x%x, bitmap_size %d\n", 
+                rp->user_ctx, rp->bitmap_size);
+
+    if (verbose) {
+            s = format (s, "  flags: 0x%x %U\n", rp->flags, 
+		format_svm_flags, rp->flags);
+            s = format (s, 
+                        "  region_heap 0x%x data_base 0x%x data_heap 0x%x\n",
+                        rp->region_heap, rp->data_base, rp->data_heap);
+    }
+
+    s = format (s, "  %d clients, pids: ",
+                vec_len(rp->client_pids));
+
+    for (i = 0; i < vec_len(rp->client_pids); i++)
+        s = format (s, "%d ", rp->client_pids[i]);
+    
+    s = format (s, "\n");
+
+    if (verbose) {
+        lo = hi = ~0;
+
+        s = format (s, "  VM in use: ");
+
+        for (i = 0; i < rp->bitmap_size; i++) {
+            if (clib_bitmap_get_no_check (rp->bitmap, i) != 0) {
+                if (lo == ~0) {
+                    hi = lo = rp->virtual_base + i*MMAP_PAGESIZE;
+                } else {
+                    hi = rp->virtual_base + i*MMAP_PAGESIZE; 
+                }
+            } else {
+                if (lo != ~0) {
+                    hi = rp->virtual_base + i*MMAP_PAGESIZE -1;
+                    s = format (s, "   0x%x - 0x%x (%dk)\n", lo, hi,
+                                (hi - lo)>>10);
+                    lo = hi = ~0;
+                }
+            }
+        }
+        s = format (s, "  rgn heap stats: %U", format_mheap, 
+                    rp->region_heap, 0);
+        if ((rp->flags & SVM_FLAGS_MHEAP) && rp->data_heap) {
+            s = format (s, "\n  data heap stats: %U", format_mheap, 
+                        rp->data_heap, 1);
+        }
+        s = format (s, "\n");
+    }
+
+    return(s);
+}
+
+/*
+ * rnd_pagesize
+ * Round to a pagesize multiple, presumably 4k works
+ */
+static unsigned int rnd_pagesize(unsigned int size)
+{
+    unsigned int rv;
+
+    rv = (size + (MMAP_PAGESIZE-1)) & ~(MMAP_PAGESIZE-1);
+    return(rv);
+}
+
+/* 
+ * svm_data_region_setup
+ */
+static int svm_data_region_create (svm_map_region_args_t *a, 
+                                   svm_region_t *rp)
+{
+    int fd;
+    u8 junk = 0;
+    uword map_size;
+
+    map_size = rp->virtual_size - (MMAP_PAGESIZE + SVM_PVT_MHEAP_SIZE);
+                
+    if (a->flags & SVM_FLAGS_FILE) {
+        struct stat statb;
+
+        fd = open (a->backing_file, O_RDWR | O_CREAT, 0777);
+
+        if (fd < 0) {
+            clib_unix_warning ("open");
+            return -1;
+        }
+
+        if (fstat(fd, &statb) < 0) {
+            clib_unix_warning("fstat");
+            return -2;
+        }
+
+        if (statb.st_mode & S_IFREG) {
+            if (statb.st_size == 0) {
+                lseek(fd, map_size, SEEK_SET);
+                if (write(fd, &junk, 1) != 1)
+                    clib_unix_warning ("set region size");
+            } else {
+                map_size = rnd_pagesize (statb.st_size);
+            }
+        } else {
+            map_size = a->backing_mmap_size;
+        }
+        
+        ASSERT(map_size <= rp->virtual_size - 
+               (MMAP_PAGESIZE + SVM_PVT_MHEAP_SIZE));
+        
+        if (mmap (rp->data_base, map_size, PROT_READ | PROT_WRITE,
+                  MAP_SHARED | MAP_FIXED, fd, 0) == MAP_FAILED) {
+            clib_unix_warning("mmap");
+            return -3;
+        }
+        close(fd);
+        rp->backing_file = (char *) format(0, "%s\0", a->backing_file);
+        rp->flags |= SVM_FLAGS_FILE;
+    }
+        
+    if (a->flags & SVM_FLAGS_MHEAP) {
+        rp->data_heap = 
+            mheap_alloc_with_flags ((void *)(rp->data_base), map_size,
+                                    MHEAP_FLAG_DISABLE_VM);
+        rp->flags |= SVM_FLAGS_MHEAP;
+    }
+    return 0;
+}
+
+static int svm_data_region_map (svm_map_region_args_t *a, 
+                                   svm_region_t *rp)
+{
+    int fd;
+    u8 junk = 0;
+    uword map_size;
+    struct stat statb;
+
+    map_size = rp->virtual_size - (MMAP_PAGESIZE + SVM_PVT_MHEAP_SIZE);
+                
+    if (a->flags & SVM_FLAGS_FILE) {
+
+        fd = open (a->backing_file, O_RDWR, 0777);
+
+        if (fd < 0) {
+            clib_unix_warning ("open");
+            return -1;
+        }
+
+        if (fstat(fd, &statb) < 0) {
+            clib_unix_warning("fstat");
+            return -2;
+        }
+
+        if (statb.st_mode & S_IFREG) {
+            if (statb.st_size == 0) {
+                lseek(fd, map_size, SEEK_SET);
+                if (write(fd, &junk, 1) != 1)
+                    clib_unix_warning ("set region size");
+            } else {
+                map_size = rnd_pagesize (statb.st_size);
+            }
+        } else {
+            map_size = a->backing_mmap_size;
+        }
+        
+        ASSERT(map_size <= rp->virtual_size 
+               - (MMAP_PAGESIZE + SVM_PVT_MHEAP_SIZE));
+        
+        if (mmap (rp->data_base, map_size, PROT_READ | PROT_WRITE,
+                  MAP_SHARED | MAP_FIXED, fd, 0) == MAP_FAILED) {
+            clib_unix_warning("mmap");
+            return -3;
+        }
+        close(fd);
+    }
+    return 0;
+}
+
+u8 *shm_name_from_svm_map_region_args (svm_map_region_args_t *a)
+{
+    u8 *path;
+    u8 *shm_name;
+    u8 *split_point;
+    u8 *mkdir_arg = 0;
+    int root_path_offset = 0;
+    int name_offset = 0;
+
+    if (a->root_path) {
+        /* Tolerate present or absent slashes */
+        if (a->root_path[0] == '/')
+            root_path_offset++;
+        
+        /* create the root_path under /dev/shm
+           iterate through path creating directories */
+
+        path = format (0, "/dev/shm/%s%c", &a->root_path[root_path_offset], 0);
+        split_point = path+1;
+        vec_add1(mkdir_arg, '-');
+        
+        while (*split_point) {
+            while (*split_point && *split_point != '/') {
+                vec_add1 (mkdir_arg, *split_point);
+                split_point++;
+            }
+            vec_add1 (mkdir_arg, 0);
+            if (mkdir ((char *) mkdir_arg, 0777) < 0 && errno != EEXIST)
+                clib_unix_warning ("mkdir %s", mkdir_arg);
+            
+            /* ready to descend another level */
+            mkdir_arg[vec_len(mkdir_arg)-1] = '-';
+            split_point++;
+        }
+        vec_free(mkdir_arg);
+        vec_free(path);
+
+        if (a->name[0] == '/')
+            name_offset = 1;
+        
+        shm_name = format (0, "/%s-%s%c", a->root_path, 
+                           &a->name[name_offset], 0);
+    }
+    else
+        shm_name = format (0, "%s%c", a->name, 0);
+    return (shm_name);
+}
+
+/*
+ * svm_map_region
+ */
+void *svm_map_region (svm_map_region_args_t *a)
+{
+    int svm_fd;
+    svm_region_t *rp;
+    pthread_mutexattr_t attr;
+    pthread_condattr_t cattr;
+    int deadman=0;
+    u8 junk = 0;
+    void *oldheap;
+    int overhead_space;
+    int rv;
+    uword data_base;
+    int nbits, words, bit;
+    int pid_holding_region_lock;
+    u8 *shm_name;
+    int dead_region_recovery = 0;
+    int time_left;
+    struct stat stat;
+    struct timespec ts, tsrem;
+
+    if (CLIB_DEBUG > 1)
+      clib_warning ("[%d] map region %s", getpid(), a->name);
+
+    ASSERT((a->size & ~(MMAP_PAGESIZE-1)) == a->size);
+    ASSERT(a->name);
+
+    shm_name = shm_name_from_svm_map_region_args (a);
+
+    svm_fd = shm_open((char *) shm_name, O_RDWR | O_CREAT | O_EXCL, 0777);
+
+    if (svm_fd >= 0) {
+
+        vec_free(shm_name);
+
+        lseek(svm_fd, a->size, SEEK_SET);
+        if (write(svm_fd, &junk, 1) != 1)
+            clib_warning ("set region size");
+
+        rp = mmap((void *)a->baseva, a->size, 
+                  PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED, svm_fd, 0);
+        
+        if (rp == (svm_region_t *) MAP_FAILED) {
+            clib_unix_warning ("mmap create");
+            return (0);
+        }
+        close(svm_fd);
+        memset(rp, 0, sizeof(*rp));
+
+        if (pthread_mutexattr_init(&attr))
+            clib_unix_warning("mutexattr_init");
+        
+        if (pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_SHARED))
+            clib_unix_warning("mutexattr_setpshared");
+
+        if (pthread_mutex_init(&rp->mutex, &attr))
+            clib_unix_warning("mutex_init");
+
+        if (pthread_mutexattr_destroy(&attr))
+            clib_unix_warning("mutexattr_destroy");
+
+        if (pthread_condattr_init(&cattr)) 
+            clib_unix_warning("condattr_init");
+
+        if (pthread_condattr_setpshared(&cattr, PTHREAD_PROCESS_SHARED))
+            clib_unix_warning("condattr_setpshared");
+
+        if (pthread_cond_init(&rp->condvar, &cattr))
+            clib_unix_warning("cond_init");
+
+        if(pthread_condattr_destroy(&cattr))
+            clib_unix_warning("condattr_destroy");
+        
+        region_lock (rp, 1);
+        
+        rp->virtual_base = a->baseva;
+        rp->virtual_size = a->size;
+
+        rp->region_heap = 
+            mheap_alloc_with_flags ((void *)(a->baseva+MMAP_PAGESIZE), 
+                                    SVM_PVT_MHEAP_SIZE, 
+                                    MHEAP_FLAG_DISABLE_VM);
+        oldheap = svm_push_pvt_heap(rp);
+
+        rp->region_name = (char *)format (0, "%s%c", a->name, 0);
+        vec_add1(rp->client_pids, getpid());
+
+        nbits = rp->virtual_size / MMAP_PAGESIZE;
+        
+        ASSERT (nbits > 0);
+        rp->bitmap_size = nbits;
+        words = (nbits + BITS(uword)-1) / BITS(uword);
+        vec_validate (rp->bitmap, words-1);
+        
+        overhead_space = MMAP_PAGESIZE /* header */ +
+            SVM_PVT_MHEAP_SIZE;
+
+        bit = 0;
+        data_base = (uword)rp->virtual_base;
+
+        if (a->flags & SVM_FLAGS_NODATA) 
+            rp->flags |= SVM_FLAGS_NEED_DATA_INIT;
+        
+        do {
+            clib_bitmap_set_no_check (rp->bitmap, bit, 1);
+            bit++;
+            overhead_space -= MMAP_PAGESIZE;
+            data_base += MMAP_PAGESIZE;
+        } while (overhead_space > 0);
+
+        rp->data_base = (void *)data_base;
+
+        /*
+         * Note: although the POSIX spec guarantees that only one
+         * process enters this block, we have to play games 
+         * to hold off clients until e.g. the mutex is ready 
+         */
+        rp->version = SVM_VERSION;
+
+        /* setup the data portion of the region */
+
+        rv = svm_data_region_create (a, rp);
+        if (rv) {
+            clib_warning ("data_region_create: %d", rv);
+        }
+
+        region_unlock(rp);
+
+        svm_pop_heap(oldheap);
+    
+        return ((void *) rp);
+    } else {
+        svm_fd = shm_open((char *)shm_name, O_RDWR, 0777);
+
+        vec_free(shm_name);
+
+        if (svm_fd < 0) {
+            perror("svm_region_map(mmap open)");
+            return (0);
+        }
+
+        time_left = 20;
+        while (1) {
+            if (0 != fstat(svm_fd, &stat)) {
+                clib_warning("fstat failed: %d", errno);
+                return (0);
+            }
+            if (stat.st_size > 0) {
+                break;
+            }
+            if (0 == time_left) {
+                clib_warning("waiting for resize of shm file timed out");
+                return (0);
+            }
+            ts.tv_sec = 0;
+            ts.tv_nsec = 100000000;
+            while (nanosleep(&ts, &tsrem) < 0)
+                ts = tsrem;
+            time_left--;
+        }
+
+        rp = mmap(0, MMAP_PAGESIZE, 
+                  PROT_READ | PROT_WRITE, MAP_SHARED, svm_fd, 0);
+
+        if (rp == (svm_region_t *) MAP_FAILED) {
+            close(svm_fd);
+            clib_warning("mmap");
+            return (0);
+        }
+        /*
+         * We lost the footrace to create this region; make sure
+         * the winner has crossed the finish line.
+         */
+        while (rp->version == 0 && deadman++ < 5) {
+            sleep(1);
+        }
+
+        /*
+         * <bleep>-ed? 
+         */
+        if (rp->version == 0) {
+            close(svm_fd);
+            munmap(rp, a->size);
+            clib_warning("rp->version %d not %d", rp->version,
+                         SVM_VERSION);
+            return (0);
+        } 
+        /* Remap now that the region has been placed */
+        a->baseva = rp->virtual_base;
+        a->size = rp->virtual_size;
+        munmap(rp, MMAP_PAGESIZE);
+
+        rp = (void *) mmap ((void *)a->baseva, a->size, 
+                            PROT_READ | PROT_WRITE, 
+                            MAP_SHARED | MAP_FIXED, svm_fd, 0);
+        if ((uword)rp == (uword)MAP_FAILED) {
+            clib_unix_warning ("mmap");
+            return (0);
+        }
+        
+        if ((uword) rp != rp->virtual_base) {
+            clib_warning("mmap botch");
+        }
+        
+        /*
+         * Try to fix the region mutex if it is held by
+         * a dead process
+         */
+        pid_holding_region_lock = rp->mutex_owner_pid;
+        if (pid_holding_region_lock &&
+            kill (pid_holding_region_lock, 0) < 0) {
+            clib_warning (
+                "region %s mutex held by dead pid %d, tag %d, force unlock",
+                rp->region_name, pid_holding_region_lock, rp->mutex_owner_tag);
+            /* owner pid is nonexistent */
+            rp->mutex.__data.__owner = 0;
+            rp->mutex.__data.__lock = 0;
+            dead_region_recovery = 1;
+        }
+
+        if (dead_region_recovery)
+            clib_warning ("recovery: attempt to re-lock region");
+
+        region_lock(rp, 2);
+        oldheap = svm_push_pvt_heap (rp);
+        vec_add1(rp->client_pids, getpid());
+        
+        if (dead_region_recovery)
+            clib_warning ("recovery: attempt svm_data_region_map");
+
+        rv = svm_data_region_map (a, rp);
+        if (rv) {
+            clib_warning ("data_region_map: %d", rv);
+        }
+
+        if (dead_region_recovery)
+            clib_warning ("unlock and continue");
+
+        region_unlock(rp);
+
+        svm_pop_heap(oldheap);
+
+        return ((void *) rp);
+
+    }
+    return 0; /* NOTREACHED */
+}
+
+static void svm_mutex_cleanup (void)
+{
+    int i;
+    for (i = 0; i < nheld; i++) {
+        pthread_mutex_unlock (mutexes_held[i]);
+    }
+}
+
+static void svm_region_init_internal (char *root_path)
+{
+    svm_region_t *rp;
+    svm_map_region_args_t *a=0;
+    u64 ticks = clib_cpu_time_now();
+    uword randomize_baseva;
+
+    /* guard against klutz calls */
+    root_rp_refcount++;
+    if (root_rp)
+        return;
+
+    atexit(svm_mutex_cleanup);
+
+    /* Randomize the shared-VM base at init time */
+    randomize_baseva = (ticks & 15) * 4096;
+
+    vec_validate(a,0);
+    a->root_path = root_path;
+    a->name = SVM_GLOBAL_REGION_NAME;
+    a->baseva = SVM_GLOBAL_REGION_BASEVA + randomize_baseva;
+    a->size = SVM_GLOBAL_REGION_SIZE;
+    a->flags = SVM_FLAGS_NODATA;
+
+    rp = svm_map_region (a);
+    ASSERT(rp);
+
+    region_lock(rp, 3);
+
+    /* Set up the main region data structures */
+    if (rp->flags & SVM_FLAGS_NEED_DATA_INIT) {
+        svm_main_region_t *mp = 0;
+        void *oldheap;
+
+        rp->flags &= ~(SVM_FLAGS_NEED_DATA_INIT);
+
+        oldheap = svm_push_pvt_heap (rp);
+        vec_validate (mp, 0);
+        mp->name_hash = hash_create_string (0, sizeof(uword));
+        mp->root_path = root_path 
+            ? format (0, "%s%c", root_path, 0) : 0 ;
+        rp->data_base = mp;
+        svm_pop_heap (oldheap);
+    }
+    region_unlock(rp);
+    vec_free (a);
+    root_rp = rp;
+}
+
+void svm_region_init (void)
+{
+    svm_region_init_internal (0);
+}
+
+void svm_region_init_chroot (char *root_path)
+{
+    svm_region_init_internal (root_path);
+}
+
+void *svm_region_find_or_create (svm_map_region_args_t *a)
+{
+    svm_main_region_t *mp;
+    svm_region_t *rp;
+    uword need_nbits;
+    int index, i;
+    void *oldheap;
+    uword *p;
+    u8 *name;
+    svm_subregion_t *subp;
+    
+    ASSERT(root_rp);
+
+    a->size +=  MMAP_PAGESIZE + SVM_PVT_MHEAP_SIZE;
+    a->size = rnd_pagesize(a->size);
+
+    region_lock (root_rp, 4);
+    oldheap = svm_push_pvt_heap(root_rp);
+    mp = root_rp->data_base;
+    
+    ASSERT(mp);
+
+    /* Map the named region from the correct chroot environment */
+    a->root_path = (char *) mp->root_path;
+
+    /* 
+     * See if this region is already known. If it is, we're
+     * almost done... 
+     */
+    p = hash_get_mem (mp->name_hash, a->name);
+
+    if (p) {
+        rp = svm_map_region (a);
+        region_unlock(root_rp);
+        svm_pop_heap (oldheap);
+        return rp;
+    }
+    
+    /* Create the region. */
+    ASSERT((a->size & ~(MMAP_PAGESIZE-1)) == a->size);
+
+    need_nbits = a->size / MMAP_PAGESIZE;
+
+    index = 1;  /* $$$ fixme, figure out how many bit to really skip */
+
+    /*
+     * Scan the virtual space allocation bitmap, looking for a large
+     * enough chunk 
+     */
+    do {
+        if (clib_bitmap_get_no_check(root_rp->bitmap, index) == 0) {
+            for (i = 0; i < (need_nbits-1); i++) {
+                if (clib_bitmap_get_no_check(root_rp->bitmap, 
+                                             index+i) == 1) {
+                    index = index + i;
+                    goto next;
+                }
+            }
+            break;
+        }
+        index++;
+    next:;
+    } while (index < root_rp->bitmap_size);
+
+    /* Completely out of VM? */
+    if (index >= root_rp->bitmap_size) {
+        clib_warning("region %s: not enough VM to allocate 0x%x",
+                     root_rp->region_name, a->size);
+        svm_pop_heap (oldheap);
+        region_unlock (root_rp);
+        return 0;
+    }
+    
+    /*
+     * Mark virtual space allocated 
+     */
+#if CLIB_DEBUG > 1
+    clib_warning ("set %d bits at index %d", need_nbits, index);
+#endif
+
+    for (i = 0; i < need_nbits; i++) {
+        clib_bitmap_set_no_check (root_rp->bitmap, index+i, 1);
+    }
+
+    /* Place this region where it goes... */
+    a->baseva = root_rp->virtual_base + index*MMAP_PAGESIZE;
+
+    rp = svm_map_region (a);
+    
+    pool_get (mp->subregions, subp);
+    name = format (0, "%s%c", a->name, 0);
+    subp->subregion_name = name;
+
+    hash_set_mem (mp->name_hash, name, subp - mp->subregions);
+
+    svm_pop_heap (oldheap);
+
+    region_unlock (root_rp);
+
+    return (rp);
+}
+
+/*
+ * svm_region_unmap
+ *
+ * Let go of the indicated region. If the calling process
+ * is the last customer, throw it away completely.
+ * The root region mutex guarantees atomicity with respect to
+ * a new region client showing up at the wrong moment.
+ */
+void svm_region_unmap (void *rp_arg)
+{
+    int i, mypid = getpid();
+    int nclients_left;
+    void *oldheap;
+    uword virtual_base, virtual_size;
+    svm_region_t *rp = rp_arg;
+    char *name;
+
+    /* 
+     * If we take a signal while holding one or more shared-memory
+     * mutexes, we may end up back here from an otherwise
+     * benign exit handler. Bail out to avoid a recursive
+     * mutex screw-up.
+     */
+    if (nheld)
+        return;
+
+    ASSERT(rp);
+    ASSERT(root_rp);
+
+    if (CLIB_DEBUG > 1)
+      clib_warning ("[%d] unmap region %s", getpid(), rp->region_name);
+
+    region_lock (root_rp, 5);
+    region_lock (rp, 6);
+    
+    oldheap = svm_push_pvt_heap (rp); /* nb vec_delete() in the loop */
+
+    /* Remove the caller from the list of mappers */
+    for (i = 0; i < vec_len(rp->client_pids); i++) {
+        if (rp->client_pids[i] == mypid) {
+            vec_delete (rp->client_pids, 1, i);
+            goto found;
+        }
+    }
+    clib_warning("pid %d AWOL", mypid);
+
+ found:
+
+    svm_pop_heap (oldheap);
+
+    nclients_left = vec_len(rp->client_pids);
+    virtual_base = rp->virtual_base;
+    virtual_size = rp->virtual_size;
+
+    if (nclients_left == 0) {
+        int index, nbits, i;
+        svm_main_region_t *mp;
+        uword *p;
+        svm_subregion_t *subp;
+
+        /* Kill the region, last guy on his way out */
+
+        oldheap = svm_push_pvt_heap (root_rp); 
+        name = vec_dup (rp->region_name);
+
+        virtual_base = rp->virtual_base;
+        virtual_size = rp->virtual_size;
+
+        /* Figure out which bits to clear in the root region bitmap */
+        index = (virtual_base - root_rp->virtual_base)
+            / MMAP_PAGESIZE;
+
+        nbits = (virtual_size + MMAP_PAGESIZE - 1)
+            / MMAP_PAGESIZE;
+
+#if CLIB_DEBUG > 1
+        clib_warning ("clear %d bits at index %d", nbits, index);
+#endif
+        /* Give back the allocated VM */
+        for (i = 0; i < nbits; i++) {
+            clib_bitmap_set_no_check (root_rp->bitmap, index+i, 0);
+        }
+
+        mp = root_rp->data_base;
+
+        p = hash_get_mem (mp->name_hash, name);
+        
+        /* Better never happen ... */
+        if (p == NULL) {
+            region_unlock (rp);
+            region_unlock (root_rp);
+            svm_pop_heap (oldheap);
+            clib_warning ("Region name '%s' not found?", name);
+            return;
+        }
+        
+        /* Remove from the root region subregion pool */
+        subp = mp->subregions + p[0];
+        pool_put (mp->subregions, subp);
+        
+        hash_unset_mem (mp->name_hash, name);
+
+        vec_free(name);
+
+        region_unlock (rp);
+        shm_unlink(rp->region_name);
+        munmap ((void *)virtual_base, virtual_size);
+        region_unlock (root_rp);
+        svm_pop_heap (oldheap);
+        return;
+    }
+
+    region_unlock(rp);
+    region_unlock(root_rp);
+
+    munmap ((void *)virtual_base, virtual_size);
+}
+
+/*
+ * svm_region_exit
+ * There is no clean way to unlink the
+ * root region when all clients go away, 
+ * so remove the pid entry and call it a day.
+ */ 
+void svm_region_exit ()
+{
+    void *oldheap;
+    int i, mypid = getpid();
+    uword virtual_base, virtual_size;
+
+    /* It felt so nice we did it twice... */
+    if (root_rp == 0)
+        return;
+
+    if (--root_rp_refcount > 0)
+        return;
+
+    /* 
+     * If we take a signal while holding one or more shared-memory
+     * mutexes, we may end up back here from an otherwise
+     * benign exit handler. Bail out to avoid a recursive
+     * mutex screw-up.
+     */
+    if (nheld)
+        return;
+
+    region_lock(root_rp, 7);
+    oldheap = svm_push_pvt_heap (root_rp);
+
+    virtual_base = root_rp->virtual_base;
+    virtual_size = root_rp->virtual_size;
+
+    for (i = 0; i < vec_len(root_rp->client_pids); i++) {
+        if (root_rp->client_pids[i] == mypid) {
+            vec_delete (root_rp->client_pids, 1, i);
+            goto found;
+        }
+    }
+    clib_warning("pid %d AWOL", mypid);
+
+ found:
+
+    region_unlock(root_rp);
+    svm_pop_heap (oldheap);
+
+    root_rp = 0;
+    munmap ((void *)virtual_base, virtual_size);
+}
+
+void svm_client_scan_this_region_nolock (svm_region_t *rp)
+{
+    int j;
+    int mypid = getpid();
+    void *oldheap;
+
+    for (j = 0; j < vec_len(rp->client_pids); j++) {
+        if (mypid == rp->client_pids[j])
+            continue;
+        if (rp->client_pids[j] && (kill (rp->client_pids[j], 0) < 0)) {
+            clib_warning ("%s: cleanup ghost pid %d",
+                          rp->region_name, rp->client_pids[j]);
+            /* nb: client vec in rp->region_heap */
+            oldheap = svm_push_pvt_heap (rp); 
+            vec_delete (rp->client_pids, 1, j);
+            j--;
+            svm_pop_heap (oldheap);
+        }
+    }
+}
+
+
+/* 
+ * Scan svm regions for dead clients
+ */
+void svm_client_scan(char *root_path)
+{
+    int i, j;
+    svm_main_region_t *mp;
+    svm_map_region_args_t *a = 0;
+    svm_region_t *root_rp;
+    svm_region_t *rp;
+    svm_subregion_t *subp;
+    u8 *name=0;
+    u8 ** svm_names=0;
+    void *oldheap;
+    int mypid = getpid();
+
+    vec_validate (a, 0);
+
+    svm_region_init_chroot(root_path);
+
+    root_rp = svm_get_root_rp();
+
+    pthread_mutex_lock (&root_rp->mutex);
+
+    mp = root_rp->data_base;
+
+    for (j = 0; j < vec_len (root_rp->client_pids); j++) {
+        if (mypid == root_rp->client_pids[j])
+            continue;
+        if (root_rp->client_pids[j] 
+            && (kill (root_rp->client_pids[j], 0) < 0)) {
+            clib_warning ("%s: cleanup ghost pid %d",
+                    root_rp->region_name, root_rp->client_pids[j]);
+            /* nb: client vec in root_rp->region_heap */
+            oldheap = svm_push_pvt_heap (root_rp); 
+            vec_delete (root_rp->client_pids, 1, j);
+            j--;
+            svm_pop_heap (oldheap);
+        }
+    }
+
+    /* 
+     * Snapshoot names, can't hold root rp mutex across
+     * find_or_create.
+     */
+    pool_foreach (subp, mp->subregions, ({
+	  name = vec_dup (subp->subregion_name);
+	  vec_add1(svm_names, name);
+	}));
+
+    pthread_mutex_unlock (&root_rp->mutex);
+
+    for (i = 0; i < vec_len(svm_names); i++) {
+	  vec_validate(a, 0);
+          a->root_path = root_path;
+	  a->name = (char *) svm_names[i];
+	  rp = svm_region_find_or_create (a);
+	  if (rp) {
+	    pthread_mutex_lock (&rp->mutex);
+
+            svm_client_scan_this_region_nolock (rp);
+
+	    pthread_mutex_unlock (&rp->mutex);
+	    svm_region_unmap (rp);
+            vec_free(svm_names[i]);
+	  }
+	  vec_free (a);
+    }
+    vec_free(svm_names);
+
+    svm_region_exit ();
+
+    vec_free (a);
+}