Merged in dstaesse/ouroboros/be-shm-robust (pull request #147)

lib: robust locking in shared memory and crash recovery

3 files changed, 279 insertions, 90 deletions

diff --git a/src/lib/dev.c b/src/lib/dev.c
index ac995b2d..19bc90e5 100644
--- a/src/lib/dev.c
+++ b/src/lib/dev.c
@@ -40,7 +40,7 @@ struct flow {
         int                   port_id;
         int                   oflags;
 
-        /* don't think this needs locking */
+        pid_t                 api;
 };
 
 struct ap_data {
@@ -93,6 +93,7 @@ int ap_init(char * ap_name)
         for (i = 0; i < AP_MAX_FLOWS; ++i) {
                 _ap_instance->flows[i].rb = NULL;
                 _ap_instance->flows[i].port_id = -1;
+                _ap_instance->flows[i].api = 0; /* API_INVALID */
         }
 
         pthread_rwlock_init(&_ap_instance->flows_lock, NULL);
@@ -319,6 +320,8 @@ int flow_alloc(char * dst_name,
 
         _ap_instance->flows[fd].port_id = recv_msg->port_id;
         _ap_instance->flows[fd].oflags  = FLOW_O_DEFAULT;
+        _ap_instance->flows[fd].api     =
+                shm_ap_rbuff_get_api(_ap_instance->flows[fd].rb);
 
         pthread_rwlock_unlock(&_ap_instance->flows_lock);
         pthread_rwlock_unlock(&_ap_instance->data_lock);
@@ -349,7 +352,7 @@ int flow_alloc_res(int fd)
                 return -ENOTALLOC;
         }
 
-        msg.port_id      = _ap_instance->flows[fd].port_id;
+        msg.port_id = _ap_instance->flows[fd].port_id;
 
         pthread_rwlock_unlock(&_ap_instance->flows_lock);
         pthread_rwlock_unlock(&_ap_instance->data_lock);
@@ -389,11 +392,12 @@ int flow_dealloc(int fd)
                 return -ENOTALLOC;
         }
 
-        msg.port_id      = _ap_instance->flows[fd].port_id;
+        msg.port_id = _ap_instance->flows[fd].port_id;
 
         _ap_instance->flows[fd].port_id = -1;
         shm_ap_rbuff_close(_ap_instance->flows[fd].rb);
         _ap_instance->flows[fd].rb = NULL;
+        _ap_instance->flows[fd].api = 0;
 
         bmp_release(_ap_instance->fds, fd);
 
@@ -476,12 +480,12 @@ ssize_t flow_write(int fd, void * buf, size_t count)
         }
 
         if (_ap_instance->flows[fd].oflags & FLOW_O_NONBLOCK) {
-                index = shm_create_du_buff(_ap_instance->dum,
-                                           count + DU_BUFF_HEADSPACE +
-                                           DU_BUFF_TAILSPACE,
-                                           DU_BUFF_HEADSPACE,
-                                           (uint8_t *) buf,
-                                           count);
+                index = shm_du_map_write(_ap_instance->dum,
+                                         _ap_instance->flows[fd].api,
+                                         DU_BUFF_HEADSPACE,
+                                         DU_BUFF_TAILSPACE,
+                                         (uint8_t *) buf,
+                                         count);
                 if (index == -1) {
                         pthread_rwlock_unlock(&_ap_instance->flows_lock);
                         pthread_rwlock_unlock(&_ap_instance->data_lock);
@@ -492,18 +496,18 @@ ssize_t flow_write(int fd, void * buf, size_t count)
                 e.port_id = _ap_instance->flows[fd].port_id;
 
                 if (shm_ap_rbuff_write(_ap_instance->flows[fd].rb, &e) < 0) {
-                        shm_release_du_buff(_ap_instance->dum, index);
+                        shm_du_map_remove(_ap_instance->dum, index);
                         pthread_rwlock_unlock(&_ap_instance->flows_lock);
                         pthread_rwlock_unlock(&_ap_instance->data_lock);
                         return -1;
                 }
         } else { /* blocking */
-                while ((index = shm_create_du_buff(_ap_instance->dum,
-                                                   count + DU_BUFF_HEADSPACE +
-                                                   DU_BUFF_TAILSPACE,
-                                                   DU_BUFF_HEADSPACE,
-                                                   (uint8_t *) buf,
-                                                   count)) < 0)
+                while ((index = shm_du_map_write(_ap_instance->dum,
+                                                 _ap_instance->flows[fd].api,
+                                                 DU_BUFF_HEADSPACE,
+                                                 DU_BUFF_TAILSPACE,
+                                                 (uint8_t *) buf,
+                                                 count)) < 0)
                         ;
 
                 e.index   = index;
@@ -555,9 +559,7 @@ ssize_t flow_read(int fd, void * buf, size_t count)
                 return -EAGAIN;
         }
 
-        n = shm_du_map_read_sdu(&sdu,
-                                _ap_instance->dum,
-                                idx);
+        n = shm_du_map_read(&sdu, _ap_instance->dum, idx);
         if (n < 0) {
                 pthread_rwlock_unlock(&_ap_instance->data_lock);
                 return -1;
@@ -565,7 +567,7 @@ ssize_t flow_read(int fd, void * buf, size_t count)
 
         memcpy(buf, sdu, MIN(n, count));
 
-        shm_release_du_buff(_ap_instance->dum, idx);
+        shm_du_map_remove(_ap_instance->dum, idx);
 
         pthread_rwlock_unlock(&_ap_instance->data_lock);
 
diff --git a/src/lib/shm_ap_rbuff.c b/src/lib/shm_ap_rbuff.c
index 69e96c40..f54627b7 100644
--- a/src/lib/shm_ap_rbuff.c
+++ b/src/lib/shm_ap_rbuff.c
@@ -26,6 +26,7 @@
 
 #include <ouroboros/logs.h>
 #include <ouroboros/shm_ap_rbuff.h>
+#include <ouroboros/shm_du_map.h>
 
 #include <pthread.h>
 #include <sys/mman.h>
@@ -34,7 +35,6 @@
 #include <string.h>
 #include <stdint.h>
 #include <unistd.h>
-#include <stdbool.h>
 #include <errno.h>
 #include <sys/stat.h>
 
@@ -127,6 +127,7 @@ struct shm_ap_rbuff * shm_ap_rbuff_create()
         rb->work      = (pthread_cond_t *) (rb->shm_mutex + 1);
 
         pthread_mutexattr_init(&mattr);
+        pthread_mutexattr_setrobust(&mattr, PTHREAD_MUTEX_ROBUST);
         pthread_mutexattr_setpshared(&mattr, PTHREAD_PROCESS_SHARED);
         pthread_mutex_init(rb->shm_mutex, &mattr);
 
@@ -213,6 +214,7 @@ void shm_ap_rbuff_close(struct shm_ap_rbuff * rb)
 void shm_ap_rbuff_destroy(struct shm_ap_rbuff * rb)
 {
         char fn[25];
+        struct shm_du_map * dum = NULL;
 
         if (rb == NULL) {
                 LOG_DBGF("Bogus input. Bugging out.");
@@ -220,8 +222,17 @@ void shm_ap_rbuff_destroy(struct shm_ap_rbuff * rb)
         }
 
         if (rb->api != getpid()) {
-                LOG_ERR("Tried to destroy other AP's rbuff.");
-                return;
+                dum = shm_du_map_open();
+                if (shm_du_map_owner(dum) == getpid()) {
+                        LOG_DBGF("Ringbuffer %d destroyed by IRMd %d.",
+                                 rb->api, getpid());
+                        shm_du_map_close(dum);
+                } else {
+                        LOG_ERR("AP-I %d tried to destroy rbuff owned by %d.",
+                                getpid(), rb->api);
+                        shm_du_map_close(dum);
+                        return;
+                }
         }
 
         if (close(rb->fd) < 0)
@@ -243,12 +254,16 @@ int shm_ap_rbuff_write(struct shm_ap_rbuff * rb, struct rb_entry * e)
         if (rb == NULL || e == NULL)
                 return -1;
 
-        pthread_mutex_lock(rb->shm_mutex);
+        if (pthread_mutex_lock(rb->shm_mutex) == EOWNERDEAD) {
+                LOG_DBGF("Recovering dead mutex.");
+                pthread_mutex_consistent(rb->shm_mutex);
+        }
 
         if (!shm_rbuff_free(rb)) {
                 pthread_mutex_unlock(rb->shm_mutex);
                 return -1;
         }
+
         if (shm_rbuff_empty(rb))
                 pthread_cond_broadcast(rb->work);
 
@@ -269,10 +284,21 @@ struct rb_entry * shm_ap_rbuff_read(struct shm_ap_rbuff * rb)
 
         pthread_cleanup_push((void(*)(void *))pthread_mutex_unlock,
                              (void *) rb->shm_mutex);
-        pthread_mutex_lock(rb->shm_mutex);
+
+        if (pthread_mutex_lock(rb->shm_mutex) == EOWNERDEAD) {
+                LOG_DBGF("Recovering dead mutex.");
+                pthread_mutex_consistent(rb->shm_mutex);
+        }
+
+        while (tail_el_ptr->port_id < 0)
+                *rb->ptr_tail = (*rb->ptr_tail + 1) & (SHM_RBUFF_SIZE -1);
 
         while(shm_rbuff_empty(rb))
-                pthread_cond_wait(rb->work, rb->shm_mutex);
+                if (pthread_cond_wait(rb->work, rb->shm_mutex)
+                    == EOWNERDEAD) {
+                LOG_DBGF("Recovering dead mutex.");
+                pthread_mutex_consistent(rb->shm_mutex);
+        }
 
         e = malloc(sizeof(*e));
         if (e == NULL) {
@@ -293,13 +319,19 @@ ssize_t shm_ap_rbuff_read_port(struct shm_ap_rbuff * rb, int port_id)
 {
         ssize_t idx = -1;
 
-        pthread_mutex_lock(rb->shm_mutex);
+        if (pthread_mutex_lock(rb->shm_mutex) == EOWNERDEAD) {
+                LOG_DBGF("Recovering dead mutex.");
+                pthread_mutex_consistent(rb->shm_mutex);
+        }
 
         if (shm_rbuff_empty(rb)) {
                 pthread_mutex_unlock(rb->shm_mutex);
                 return -1;
         }
 
+        while (tail_el_ptr->port_id < 0)
+                *rb->ptr_tail = (*rb->ptr_tail + 1) & (SHM_RBUFF_SIZE -1);
+
         if (tail_el_ptr->port_id != port_id) {
                 pthread_mutex_unlock(rb->shm_mutex);
                 return -1;
@@ -313,3 +345,27 @@ ssize_t shm_ap_rbuff_read_port(struct shm_ap_rbuff * rb, int port_id)
 
         return idx;
 }
+
+pid_t shm_ap_rbuff_get_api(struct shm_ap_rbuff *rb)
+{
+        pid_t api = 0;
+        if (rb == NULL)
+                return 0;
+
+        pthread_mutex_lock(rb->shm_mutex);
+        api = rb->api;
+        pthread_mutex_unlock(rb->shm_mutex);
+
+        return api;
+}
+
+void shm_ap_rbuff_reset(struct shm_ap_rbuff * rb)
+{
+        if (rb == NULL)
+                return;
+
+        pthread_mutex_lock(rb->shm_mutex);
+        *rb->ptr_tail = 0;
+        *rb->ptr_head = 0;
+        pthread_mutex_unlock(rb->shm_mutex);
+}
diff --git a/src/lib/shm_du_map.c b/src/lib/shm_du_map.c
index 2a316265..24adac1a 100644
--- a/src/lib/shm_du_map.c
+++ b/src/lib/shm_du_map.c
@@ -23,11 +23,14 @@
 
 #include <ouroboros/config.h>
 #include <ouroboros/shm_du_map.h>
+#include <ouroboros/shm_ap_rbuff.h>
+#include <ouroboros/time_utils.h>
 #include <pthread.h>
 #include <sys/mman.h>
 #include <fcntl.h>
 #include <stdlib.h>
 #include <string.h>
+#include <signal.h>
 #include <sys/stat.h>
 
 #define OUROBOROS_PREFIX "shm_du_map"
@@ -35,8 +38,8 @@
 #include <ouroboros/logs.h>
 
 #define SHM_BLOCKS_SIZE (SHM_BLOCKS_IN_MAP * SHM_DU_BUFF_BLOCK_SIZE)
-#define SHM_FILE_SIZE (SHM_BLOCKS_SIZE + 2 * sizeof (size_t)                   \
-                       + sizeof(pthread_mutex_t) + sizeof(pthread_cond_t)      \
+#define SHM_FILE_SIZE (SHM_BLOCKS_SIZE + 3 * sizeof (size_t)                   \
+                       + sizeof(pthread_mutex_t) + 2 * sizeof(pthread_cond_t)  \
                        + sizeof(pid_t))
 
 #define get_head_ptr(dum)                                                      \
@@ -57,6 +60,8 @@
                           & (SHM_BLOCKS_IN_MAP - 1))
 #define shm_map_free(dum, i)(shm_map_used(dum) + i < SHM_BLOCKS_IN_MAP)
 
+#define shm_map_empty(dum) (*dum->ptr_tail == *dum->ptr_head)
+
 #define sdu_size(dum, idx) (idx_to_du_buff_ptr(dum, idx)->du_tail -            \
                             idx_to_du_buff_ptr(dum, idx)->du_head)
 
@@ -66,7 +71,7 @@ struct shm_du_buff {
         size_t size;
         size_t du_head;
         size_t du_tail;
-        size_t garbage;
+        pid_t  dst_api;
 };
 
 struct shm_du_map {
@@ -74,11 +79,80 @@ struct shm_du_map {
         size_t *          ptr_head;    /* start of ringbuffer head */
         size_t *          ptr_tail;    /* start of ringbuffer tail */
         pthread_mutex_t * shm_mutex;   /* lock all free space in shm */
-        pthread_cond_t *  sanitize;    /* run sanitizer when buffer full */
+        size_t *          choked;      /* stale sdu detection */
+        pthread_cond_t *  healthy;     /* du map is healthy */
+        pthread_cond_t *  full;        /* run sanitizer when buffer full */
         pid_t *           api;         /* api of the irmd owner */
         int               fd;
 };
 
+static void garbage_collect(struct shm_du_map * dum)
+{
+#ifndef SHM_MAP_SINGLE_BLOCK
+        long sz;
+        long blocks;
+#endif
+        while (get_tail_ptr(dum)->dst_api == 0 &&
+               !shm_map_empty(dum)) {
+#ifndef SHM_MAP_SINGLE_BLOCK
+                blocks = 0;
+                sz = get_tail_ptr(dum)->size +
+                        (long) sizeof(struct shm_du_buff);
+                while (sz > 0) {
+                        sz -= SHM_DU_BUFF_BLOCK_SIZE;
+                        ++blocks;
+                }
+
+                *dum->ptr_tail =
+                        (*dum->ptr_tail + blocks) & (SHM_BLOCKS_IN_MAP - 1);
+
+#else
+                *dum->ptr_tail =
+                        (*dum->ptr_tail + 1) & (SHM_BLOCKS_IN_MAP - 1);
+#endif
+        }
+}
+
+static void clean_sdus(struct shm_du_map * dum, pid_t api)
+{
+        size_t idx = *dum->ptr_tail;
+        struct shm_du_buff * buf;
+#ifndef SHM_DU_MAP_SINGLE_BLOCK
+        long sz;
+        long blocks = 0;
+#endif
+
+        while (idx != *dum->ptr_head) {
+                buf = idx_to_du_buff_ptr(dum, idx);
+                if (buf->dst_api == api)
+                        buf->dst_api = 0;
+
+#ifndef SHM_DU_MAP_SINGLE_BLOCK
+                blocks = 0;
+                sz = get_tail_ptr(dum)->size + (long) sizeof(struct shm_du_buff);
+                while (sz > 0) {
+                        sz -= SHM_DU_BUFF_BLOCK_SIZE;
+                        ++blocks;
+                }
+
+                idx = (idx + blocks) & (SHM_BLOCKS_IN_MAP - 1);
+#else
+                idx = (idx + 1) & (SHM_BLOCKS_IN_MAP - 1);
+#endif
+        }
+
+        garbage_collect(dum);
+
+        if (kill(api, 0) == 0) {
+                struct shm_ap_rbuff * rb;
+                rb = shm_ap_rbuff_open(api);
+                shm_ap_rbuff_reset(rb);
+                shm_ap_rbuff_close(rb);
+        }
+
+        *dum->choked = 0;
+}
+
 struct shm_du_map * shm_du_map_create()
 {
         struct shm_du_map * dum;
@@ -140,8 +214,10 @@ struct shm_du_map * shm_du_map_create()
                 ((uint8_t *) dum->shm_base + SHM_BLOCKS_SIZE);
         dum->ptr_tail = dum->ptr_head + 1;
         dum->shm_mutex = (pthread_mutex_t *) (dum->ptr_tail + 1);
-        dum->sanitize = (pthread_cond_t *) (dum->shm_mutex + 1);
-        dum->api = (pid_t *) (dum->sanitize + 1);
+        dum->choked = (size_t *) (dum->shm_mutex + 1);
+        dum->healthy = (pthread_cond_t *) (dum->choked + 1);
+        dum->full = dum->healthy + 1;
+        dum->api = (pid_t *) (dum->full + 1);
 
         pthread_mutexattr_init(&mattr);
         pthread_mutexattr_setpshared(&mattr, PTHREAD_PROCESS_SHARED);
@@ -150,11 +226,14 @@ struct shm_du_map * shm_du_map_create()
 
         pthread_condattr_init(&cattr);
         pthread_condattr_setpshared(&cattr, PTHREAD_PROCESS_SHARED);
-        pthread_cond_init(dum->sanitize, &cattr);
+        pthread_cond_init(dum->full, &cattr);
+        pthread_cond_init(dum->healthy, &cattr);
 
         *dum->ptr_head = 0;
         *dum->ptr_tail = 0;
 
+        *dum->choked = 0;
+
         *dum->api = getpid();
 
         dum->fd = shm_fd;
@@ -202,8 +281,10 @@ struct shm_du_map * shm_du_map_open()
                 ((uint8_t *) dum->shm_base + SHM_BLOCKS_SIZE);
         dum->ptr_tail = dum->ptr_head + 1;
         dum->shm_mutex = (pthread_mutex_t *) (dum->ptr_tail + 1);
-        dum->sanitize = (pthread_cond_t *) (dum->shm_mutex + 1);
-        dum->api = (pid_t *) (dum->sanitize + 1);
+        dum->choked = (size_t *) (dum->shm_mutex + 1);
+        dum->healthy = (pthread_cond_t *) (dum->choked + 1);
+        dum->full = dum->healthy + 1;
+        dum->api = (pid_t *) (dum->full + 1);
 
         dum->fd = shm_fd;
 
@@ -212,12 +293,73 @@ struct shm_du_map * shm_du_map_open()
 
 pid_t shm_du_map_owner(struct shm_du_map * dum)
 {
+        if (dum == NULL)
+                return 0;
+
         return *dum->api;
 }
 
 void * shm_du_map_sanitize(void * o)
 {
-        LOG_MISSING;
+        struct shm_du_map * dum = (struct shm_du_map *) o;
+        struct timespec intv
+                = {SHM_DU_TIMEOUT_MICROS / MILLION,
+                   (SHM_DU_TIMEOUT_MICROS % MILLION) * 1000};
+
+        pid_t   api;
+
+        if (dum == NULL)
+                return (void *) -1;
+        if (pthread_mutex_lock(dum->shm_mutex) == EOWNERDEAD) {
+                LOG_WARN("Recovering dead mutex.");
+                pthread_mutex_consistent(dum->shm_mutex);
+        }
+
+        pthread_cleanup_push((void (*)(void *)) pthread_mutex_unlock,
+                             (void *) dum->shm_mutex);
+
+        while (true) {
+                int ret = 0;
+                if (pthread_cond_wait(dum->full, dum->shm_mutex)
+                        == EOWNERDEAD) {
+                        LOG_WARN("Recovering dead mutex.");
+                        pthread_mutex_consistent(dum->shm_mutex);
+                }
+
+                *dum->choked = 1;
+
+                api = get_tail_ptr(dum)->dst_api;
+
+                if (kill(api, 0) == 0) {
+                        struct timespec now;
+                        struct timespec dl;
+                        clock_gettime(CLOCK_REALTIME, &now);
+                        ts_add(&now, &intv, &dl);
+                        while (*dum->choked) {
+                                ret = pthread_cond_timedwait(dum->healthy,
+                                                                 dum->shm_mutex,
+                                                                 &dl);
+                                if (!ret)
+                                        continue;
+
+                                if (ret == EOWNERDEAD) {
+                                        LOG_WARN("Recovering dead mutex.");
+                                        pthread_mutex_consistent(dum->shm_mutex);
+                                }
+
+                                if (ret == ETIMEDOUT) {
+                                        LOG_DBGF("SDU timed out.");
+                                        clean_sdus(dum, api);
+                                }
+                        }
+                } else {
+                        LOG_DBGF("Dead process %d left stale sdu. sg %d", api,ret);
+                        clean_sdus(dum, api);
+                }
+        }
+
+        pthread_cleanup_pop(true);
+
         return (void *) 0;
 }
 
@@ -256,21 +398,23 @@ void shm_du_map_destroy(struct shm_du_map * dum)
         free(dum);
 }
 
-ssize_t shm_create_du_buff(struct shm_du_map * dum,
-                           size_t              size,
-                           size_t              headspace,
-                           uint8_t *           data,
-                           size_t              len)
+ssize_t shm_du_map_write(struct shm_du_map * dum,
+                         pid_t               dst_api,
+                         size_t              headspace,
+                         size_t              tailspace,
+                         uint8_t *           data,
+                         size_t              len)
 {
         struct shm_du_buff * sdb;
 #ifndef SHM_MAP_SINGLE_BLOCK
         long                 blocks = 0;
-        int                  sz = size + sizeof *sdb;
-        int                  sz2 = headspace + len + sizeof *sdb;
+        size_t               size = headspace + len + tailspace;
+        int                  sz = headspace + len + sizeof *sdb;
+        int                  sz2 = sz + tailspace;
         size_t               copy_len;
 #endif
         uint8_t *            write_pos;
-        ssize_t              index;
+        ssize_t              index = -1;
 
         if (dum == NULL || data == NULL) {
                 LOG_DBGF("Bogus input, bugging out.");
@@ -294,36 +438,35 @@ ssize_t shm_create_du_buff(struct shm_du_map * dum,
                 return -1;
         }
 
-        pthread_mutex_lock(dum->shm_mutex);
+        if (pthread_mutex_lock(dum->shm_mutex) == EOWNERDEAD) {
+                LOG_DBGF("Recovering dead mutex.");
+                pthread_mutex_consistent(dum->shm_mutex);
+        }
 
 #ifndef SHM_MAP_SINGLE_BLOCK
-        while (sz > 0) {
-                sz -= SHM_DU_BUFF_BLOCK_SIZE;
+        while (sz2 > 0) {
                 sz2 -= SHM_DU_BUFF_BLOCK_SIZE;
-                if (sz2 < 0 && sz > 0) {
+                sz -= SHM_DU_BUFF_BLOCK_SIZE;
+                if (sz < 0 && sz2 > 0) {
                         pthread_mutex_unlock(dum->shm_mutex);
-                        LOG_DBG("Can't handle this packet now");
-                        return -1;
+                        LOG_DBG("Can't handle this packet now.");
+                        return -EAGAIN;
                 }
                 ++blocks;
         }
 
         if (!shm_map_free(dum, blocks)) {
-                pthread_mutex_unlock(dum->shm_mutex);
-                pthread_cond_signal(dum->sanitize);
-                return -1;
-        }
 #else
         if (!shm_map_free(dum, 1)) {
+#endif
+                pthread_cond_signal(dum->full);
                 pthread_mutex_unlock(dum->shm_mutex);
-                ptrhead_cond_signal(dum->sanitize);
                 return -1;
         }
-#endif
 
         sdb = get_head_ptr(dum);
         sdb->size = size;
-        sdb->garbage = 0;
+        sdb->dst_api = dst_api;
         sdb->du_head = headspace;
         sdb->du_tail = sdb->du_head + len;
 
@@ -333,7 +476,7 @@ ssize_t shm_create_du_buff(struct shm_du_map * dum,
         copy_len = MIN(len, SHM_DU_BUFF_BLOCK_SIZE - headspace - sizeof *sdb);
         while (blocks > 0) {
                 memcpy(write_pos, data, copy_len);
-                *(dum->ptr_head) = (*dum->ptr_head + 1)
+                *dum->ptr_head = (*dum->ptr_head + 1)
                         & (SHM_BLOCKS_IN_MAP - 1);
                 len -= copy_len;
                 copy_len = MIN(len, SHM_DU_BUFF_BLOCK_SIZE);
@@ -346,7 +489,7 @@ ssize_t shm_create_du_buff(struct shm_du_map * dum,
 #else
         memcpy(write_pos, data, len);
         index = *dum->ptr_head;
-        *(dum->ptr_head) = (*dum->ptr_head + 1) & (SHM_BLOCKS_IN_MAP - 1);
+        *dum->ptr_head = (*dum->ptr_head + 1) & (SHM_BLOCKS_IN_MAP - 1);
 #endif
         pthread_mutex_unlock(dum->shm_mutex);
 
@@ -354,18 +497,21 @@ ssize_t shm_create_du_buff(struct shm_du_map * dum,
 }
 
 /* FIXME: this cannot handle packets stretching beyond the ringbuffer border */
-int shm_du_map_read_sdu(uint8_t **          dst,
-                        struct shm_du_map * dum,
-                        ssize_t             idx)
+int shm_du_map_read(uint8_t **          dst,
+                    struct shm_du_map * dum,
+                    ssize_t             idx)
 {
         size_t len = 0;
 
         if (idx > SHM_BLOCKS_IN_MAP)
                 return -1;
 
-        pthread_mutex_lock(dum->shm_mutex);
+        if (pthread_mutex_lock(dum->shm_mutex) == EOWNERDEAD) {
+                LOG_DBGF("Recovering dead mutex.");
+                pthread_mutex_consistent(dum->shm_mutex);
+        }
 
-        if (*dum->ptr_head == *dum->ptr_tail) {
+        if (shm_map_empty(dum)) {
                 pthread_mutex_unlock(dum->shm_mutex);
                 return -1;
         }
@@ -380,47 +526,32 @@ int shm_du_map_read_sdu(uint8_t **          dst,
         return len;
 }
 
-int shm_release_du_buff(struct shm_du_map * dum, ssize_t idx)
+int shm_du_map_remove(struct shm_du_map * dum, ssize_t idx)
 {
-#ifndef SHM_MAP_SINGLE_BLOCK
-        long sz;
-        long blocks = 0;
-#endif
         if (idx > SHM_BLOCKS_IN_MAP)
                 return -1;
 
-        pthread_mutex_lock(dum->shm_mutex);
+        if (pthread_mutex_lock(dum->shm_mutex) == EOWNERDEAD) {
+                LOG_DBGF("Recovering dead mutex.");
+                pthread_mutex_consistent(dum->shm_mutex);
+        }
 
-        if (*dum->ptr_head == *dum->ptr_tail) {
+        if (shm_map_empty(dum)) {
                 pthread_mutex_unlock(dum->shm_mutex);
                 return -1;
         }
 
-        idx_to_du_buff_ptr(dum, idx)->garbage = 1;
+        idx_to_du_buff_ptr(dum, idx)->dst_api = 0;
 
         if (idx != *dum->ptr_tail) {
                 pthread_mutex_unlock(dum->shm_mutex);
                 return 0;
         }
 
-        while (get_tail_ptr(dum)->garbage == 1 &&
-               *dum->ptr_tail != *dum->ptr_head) {
-#ifndef SHM_MAP_SINGLE_BLOCK
-                sz = get_tail_ptr(dum)->size;
-                while (sz + (long) sizeof(struct shm_du_buff) > 0) {
-                        sz -= SHM_DU_BUFF_BLOCK_SIZE;
-                        ++blocks;
-                }
+        garbage_collect(dum);
 
-                *(dum->ptr_tail) =
-                        (*dum->ptr_tail + blocks) & (SHM_BLOCKS_IN_MAP - 1);
-
-                blocks = 0;
-#else
-                *(dum->ptr_tail) =
-                        (*dum->ptr_tail + 1) & (SHM_BLOCKS_IN_MAP - 1);
-#endif
-        }
+        *dum->choked = 0;
+        pthread_cond_signal(dum->healthy);
 
         pthread_mutex_unlock(dum->shm_mutex);