Imported Upstream version 3.2.2

[debian/gnuradio] / gcell / lib / runtime / spu / gc_spu_jd_queue.c

diff --git a/gcell/lib/runtime/spu/gc_spu_jd_queue.c b/gcell/lib/runtime/spu/gc_spu_jd_queue.c
new file mode 100644 (file)
index 0000000..91bb5bc
--- /dev/null
+++ b/gcell/lib/runtime/spu/gc_spu_jd_queue.c
@@ -0,0 +1,123 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2007,2008,2009 Free Software Foundation, Inc.
+ * 
+ * This file is part of GNU Radio
+ * 
+ * GNU Radio is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3, or (at your option)
+ * any later version.
+ * 
+ * GNU Radio is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <gcell/spu/gc_jd_queue.h>
+#include <gcell/spu/gc_delay.h>
+#include <gcell/spu/gc_random.h>
+#include "mutex_lock.h"
+#include "mutex_unlock.h"
+
+#define MIN(a,b) ((a) < (b) ? (a) : (b))
+
+extern int gc_sys_tag;
+
+// keep track of stats
+int jdq_ok;
+int jdq_empty;
+int jdq_locked;
+
+
+#define        INITIAL_BACKOFF    32.0
+#define MAX_BACKOFF     8192.0         /* 2.6us */
+#define        RANDOM_WEIGHT       0.2
+
+static float
+next_backoff(float backoff)
+{
+  // exponential with random
+  float t = backoff * 2.0;
+  if (t > MAX_BACKOFF)
+    t = MAX_BACKOFF;
+
+  float r = (RANDOM_WEIGHT * (2.0 * (gc_uniform_deviate() - 0.5)));
+  t = t * (1.0 + r);
+
+  return t;
+}
+
+gc_dequeue_status_t
+gc_jd_queue_dequeue(gc_eaddr_t q, gc_eaddr_t *item_ea,
+                   int jd_tag, gc_job_desc_t *item)
+{
+  int  status;
+  char         _tmp[256];
+  gc_jd_queue_t *local_q =
+    (gc_jd_queue_t *) ALIGN(_tmp, 128);                // get cache-aligned buffer
+  
+  float backoff = next_backoff(INITIAL_BACKOFF);
+
+  do {
+    // Copy the queue structure in and get a lock line reservation.
+    // (The structure is 128-byte aligned and completely fills a cache-line)
+
+    mfc_getllar(local_q, q, 0, 0);
+    spu_readch(MFC_RdAtomicStat);
+
+    if (local_q->mutex != 0){          // somebody else has it locked
+      jdq_locked++;
+      return GCQ_LOCKED;
+    }
+
+    if (local_q->head == 0){           // the queue is empty
+      jdq_empty++;
+      return GCQ_EMPTY;
+    }
+
+    // Try to acquire the lock
+
+    local_q->mutex = 1;
+    mfc_putllc(local_q, q, 0, 0);
+    status = spu_readch(MFC_RdAtomicStat);
+
+    if (status != 0){
+      gc_cdelay((int) backoff);
+      backoff = next_backoff(backoff);
+    }
+
+  } while (status != 0);
+
+  // we're now holding the lock
+    
+  // copy in job descriptor at head of queue
+  *item_ea = local_q->head;
+  
+  // We must use the fence with the jd_tag to ensure that any
+  // previously initiated put of a job desc is locally ordered before
+  // the get of the new one.
+  mfc_getf(item, local_q->head, sizeof(gc_job_desc_t), jd_tag, 0, 0);
+  mfc_write_tag_mask(1 << jd_tag);     // the tag we're interested in
+  mfc_read_tag_status_all();           // wait for DMA to complete
+
+  local_q->head = item->sys.next;
+  item->sys.next = 0;
+  if (local_q->head == 0)              // now empty?
+    local_q->tail = 0;
+
+  // Copy the queue struct back out and unlock the mutex in one fell swoop.
+  // We use the unconditional put since it's faster and we own the lock.
+
+  local_q->mutex = 0;
+  mfc_putlluc(local_q, q, 0, 0);
+  spu_readch(MFC_RdAtomicStat);
+
+  jdq_ok++;
+  return GCQ_OK;
+}