Add callback multiplex support

Change-Id: Iddeb3a1b0e20706e72ec8f74dabc60b342f003ba
Signed-off-by: Dave Barach <dave@barachs.net>

6 files changed, 177 insertions, 27 deletions

diff --git a/src/plugins/perfmon/perfmon_periodic.c b/src/plugins/perfmon/perfmon_periodic.c
index d21b464b07b..ac68c42c219 100644
--- a/src/plugins/perfmon/perfmon_periodic.c
+++ b/src/plugins/perfmon/perfmon_periodic.c
@@ -52,12 +52,18 @@ read_current_perf_counters (vlib_main_t * vm, u64 * c0, u64 * c1,
       else
 	{
 	  u64 sw_value;
-	  if (read (pm->pm_fds[i][my_thread_index], &sw_value,
-		    sizeof (sw_value)) != sizeof (sw_value))
+	  int read_result;
+	  if ((read_result = read (pm->pm_fds[i][my_thread_index], &sw_value,
+				   sizeof (sw_value)) != sizeof (sw_value)))
 	    {
 	      clib_unix_warning
-		("counter read failed, disable collection...");
-	      vm->vlib_node_runtime_perf_counter_cb = 0;
+		("counter read returned %d, expected %d",
+		 read_result, sizeof (sw_value));
+	      clib_callback_enable_disable
+		(vm->vlib_node_runtime_perf_counter_cbs,
+		 vm->vlib_node_runtime_perf_counter_cb_tmp,
+		 vm->worker_thread_main_loop_callback_lock,
+		 read_current_perf_counters, 0 /* enable */ );
 	      return;
 	    }
 	  *cc = sw_value;
@@ -202,7 +208,11 @@ enable_current_events (perfmon_main_t * pm)
 
   pm->n_active = i;
   /* Enable the main loop counter snapshot mechanism */
-  vm->vlib_node_runtime_perf_counter_cb = read_current_perf_counters;
+  clib_callback_enable_disable
+    (vm->vlib_node_runtime_perf_counter_cbs,
+     vm->vlib_node_runtime_perf_counter_cb_tmp,
+     vm->worker_thread_main_loop_callback_lock,
+     read_current_perf_counters, 1 /* enable */ );
 }
 
 static void
@@ -213,7 +223,11 @@ disable_events (perfmon_main_t * pm)
   int i;
 
   /* Stop main loop collection */
-  vm->vlib_node_runtime_perf_counter_cb = 0;
+  clib_callback_enable_disable
+    (vm->vlib_node_runtime_perf_counter_cbs,
+     vm->vlib_node_runtime_perf_counter_cb_tmp,
+     vm->worker_thread_main_loop_callback_lock,
+     read_current_perf_counters, 0 /* enable */ );
 
   for (i = 0; i < pm->n_active; i++)
     {
@@ -239,16 +253,22 @@ worker_thread_start_event (vlib_main_t * vm)
 {
   perfmon_main_t *pm = &perfmon_main;
 
+  clib_callback_enable_disable (vm->worker_thread_main_loop_callbacks,
+				vm->worker_thread_main_loop_callback_tmp,
+				vm->worker_thread_main_loop_callback_lock,
+				worker_thread_start_event, 0 /* enable */ );
   enable_current_events (pm);
-  vm->worker_thread_main_loop_callback = 0;
 }
 
 static void
 worker_thread_stop_event (vlib_main_t * vm)
 {
   perfmon_main_t *pm = &perfmon_main;
+  clib_callback_enable_disable (vm->worker_thread_main_loop_callbacks,
+				vm->worker_thread_main_loop_callback_tmp,
+				vm->worker_thread_main_loop_callback_lock,
+				worker_thread_stop_event, 0 /* enable */ );
   disable_events (pm);
-  vm->worker_thread_main_loop_callback = 0;
 }
 
 static void
@@ -285,8 +305,11 @@ start_event (perfmon_main_t * pm, f64 now, uword event_data)
 	continue;
 
       if (all || clib_bitmap_get (pm->thread_bitmap, i))
-	vlib_mains[i]->worker_thread_main_loop_callback = (void *)
-	  worker_thread_start_event;
+	clib_callback_enable_disable
+	  (vlib_mains[i]->worker_thread_main_loop_callbacks,
+	   vlib_mains[i]->worker_thread_main_loop_callback_tmp,
+	   vlib_mains[i]->worker_thread_main_loop_callback_lock,
+	   (void *) worker_thread_start_event, 1 /* enable */ );
     }
 }
 
@@ -445,8 +468,11 @@ handle_timeout (vlib_main_t * vm, perfmon_main_t * pm, f64 now)
       if (vlib_mains[i] == 0)
 	continue;
       if (all || clib_bitmap_get (pm->thread_bitmap, i))
-	vlib_mains[i]->worker_thread_main_loop_callback = (void *)
-	  worker_thread_stop_event;
+	clib_callback_enable_disable
+	  (vlib_mains[i]->worker_thread_main_loop_callbacks,
+	   vlib_mains[i]->worker_thread_main_loop_callback_tmp,
+	   vlib_mains[i]->worker_thread_main_loop_callback_lock,
+	   (void *) worker_thread_stop_event, 1 /* enable */ );
     }
 
   /* Make sure workers have stopped collection */
@@ -457,7 +483,10 @@ handle_timeout (vlib_main_t * vm, perfmon_main_t * pm, f64 now)
       for (i = 1; i < vec_len (vlib_mains); i++)
 	{
 	  /* Has the worker actually stopped collecting data? */
-	  while (vlib_mains[i]->worker_thread_main_loop_callback)
+	  while (clib_callback_is_set
+		 (vlib_mains[i]->worker_thread_main_loop_callbacks,
+		  vlib_mains[i]->worker_thread_main_loop_callback_lock,
+		  read_current_perf_counters))
 	    {
 	      if (vlib_time_now (vm) > deadman)
 		{
@@ -486,8 +515,11 @@ handle_timeout (vlib_main_t * vm, perfmon_main_t * pm, f64 now)
       if (vlib_mains[i] == 0)
 	continue;
       if (all || clib_bitmap_get (pm->thread_bitmap, i))
-	vlib_mains[i]->worker_thread_main_loop_callback = (void *)
-	  worker_thread_start_event;
+	clib_callback_enable_disable
+	  (vlib_mains[i]->worker_thread_main_loop_callbacks,
+	   vlib_mains[i]->worker_thread_main_loop_callback_tmp,
+	   vlib_mains[i]->worker_thread_main_loop_callback_lock,
+	   worker_thread_start_event, 1 /* enable */ );
     }
 }
 
diff --git a/src/vlib/main.c b/src/vlib/main.c
index 759c1d0ec0d..b6006e8bab0 100644
--- a/src/vlib/main.c
+++ b/src/vlib/main.c
@@ -687,9 +687,9 @@ vlib_node_runtime_perf_counter (vlib_main_t * vm, u64 * pmc0, u64 * pmc1,
 {
   *pmc0 = 0;
   *pmc1 = 0;
-  if (PREDICT_FALSE (vm->vlib_node_runtime_perf_counter_cb != 0))
-    (*vm->vlib_node_runtime_perf_counter_cb) (vm, pmc0, pmc1, node,
-					      frame, before_or_after);
+  if (PREDICT_FALSE (vec_len (vm->vlib_node_runtime_perf_counter_cbs) != 0))
+    clib_call_callbacks (vm->vlib_node_runtime_perf_counter_cbs, vm, pmc0,
+			 pmc1, node, frame, before_or_after);
 }
 
 always_inline void
@@ -1760,9 +1760,8 @@ vlib_main_or_worker_loop (vlib_main_t * vm, int is_main)
 	      else
 		frame_queue_check_counter--;
 	    }
-	  if (PREDICT_FALSE (vm->worker_thread_main_loop_callback != 0))
-	    ((void (*)(vlib_main_t *)) vm->worker_thread_main_loop_callback)
-	      (vm);
+	  if (PREDICT_FALSE (vec_len (vm->worker_thread_main_loop_callbacks)))
+	    clib_call_callbacks (vm->worker_thread_main_loop_callbacks, vm);
 	}
 
       /* Process pre-input nodes. */
diff --git a/src/vlib/main.h b/src/vlib/main.h
index 42f0c5196da..9b6311601d3 100644
--- a/src/vlib/main.h
+++ b/src/vlib/main.h
@@ -94,11 +94,14 @@ typedef struct vlib_main_t
   u32 node_counts_per_main_loop[2];
 
   /* Main loop hw / sw performance counters */
-  void (*vlib_node_runtime_perf_counter_cb) (struct vlib_main_t *,
-					     u64 *, u64 *,
-					     vlib_node_runtime_t *,
-					     vlib_frame_t *, int);
-
+  void (**vlib_node_runtime_perf_counter_cbs) (struct vlib_main_t *,
+					       u64 *, u64 *,
+					       vlib_node_runtime_t *,
+					       vlib_frame_t *, int);
+  void (**vlib_node_runtime_perf_counter_cb_tmp) (struct vlib_main_t *,
+						  u64 *, u64 *,
+						  vlib_node_runtime_t *,
+						  vlib_frame_t *, int);
   /* Every so often we switch to the next counter. */
 #define VLIB_LOG2_MAIN_LOOPS_PER_STATS_UPDATE 7
 
@@ -215,7 +218,10 @@ typedef struct vlib_main_t
   u8 **argv;
 
   /* Top of (worker) dispatch loop callback */
-  volatile void (*worker_thread_main_loop_callback) (struct vlib_main_t *);
+  void (**volatile worker_thread_main_loop_callbacks) (struct vlib_main_t *);
+  void (**volatile worker_thread_main_loop_callback_tmp)
+    (struct vlib_main_t *);
+  clib_spinlock_t worker_thread_main_loop_callback_lock;
 
   /* debugging */
   volatile int parked_at_barrier;
diff --git a/src/vlib/vlib.h b/src/vlib/vlib.h
index b5fe47b3729..8f59cae2cee 100644
--- a/src/vlib/vlib.h
+++ b/src/vlib/vlib.h
@@ -42,6 +42,7 @@
 
 #include <vppinfra/clib.h>
 #include <vppinfra/elf_clib.h>
+#include <vppinfra/callback.h>
 
 /* Generic definitions. */
 #include <vlib/defs.h>
diff --git a/src/vppinfra/CMakeLists.txt b/src/vppinfra/CMakeLists.txt
index 02e5322e1fc..a42bcb818a5 100644
--- a/src/vppinfra/CMakeLists.txt
+++ b/src/vppinfra/CMakeLists.txt
@@ -99,6 +99,7 @@ set(VPPINFRA_HEADERS
   bitops.h
   byte_order.h
   cache.h
+  callback.h
   clib_error.h
   clib.h
   cpu.h
diff --git a/src/vppinfra/callback.h b/src/vppinfra/callback.h
new file mode 100644
index 00000000000..595d69d72ab
--- /dev/null
+++ b/src/vppinfra/callback.h
@@ -0,0 +1,111 @@
+/*
+ * Copyright (c) 2019 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.
+ */
+
+/** @file
+ * @brief Callback multiplex scheme
+ * For a fully worked-out example, see .../src/vlib/main.[ch] and
+ * .../src/plugins/perfmon.c
+ */
+
+#ifndef included_callback_h
+#define included_callback_h
+#include <vppinfra/clib.h>
+
+/** @brief Add or remove a callback to the specified callback set
+ *  @param h head of the callback vector
+ *  @param tmp vector to build result
+ *  @param l clib_spinlock_t lock to protect the vector, may be 0
+ *  @param f function to add or remove
+ *  @param enable 1 adds f to the vector, 0 removes f from the vector
+ *
+ * Add or remove a callback from the indicated callback vector.
+ * Caller must provide locking to prevent > 1 concurrent writer
+ * Swaps the head of the callback vector and a tmp vector in one
+ * motion, after a write barrier to ensure that the write is atomic.
+ */
+#define clib_callback_enable_disable(h,tmp,l,f,enable)  \
+do {                                                    \
+  void *tmp2;                                           \
+  clib_spinlock_lock_if_init(&l);                       \
+  vec_reset_length(tmp);                                \
+  vec_append(tmp, h);                                   \
+  if (enable)                                           \
+    vec_add1 (tmp,(void *)f);                           \
+  else                                                  \
+    {                                                   \
+      int i;                                            \
+      for (i = 0; i < vec_len (tmp); i++)               \
+        if (((void *)tmp[i]) == (void *)f)              \
+          {                                             \
+            vec_delete (tmp, 1, i);                     \
+            break;                                      \
+          }                                             \
+    }                                                   \
+  tmp2 = h;                                             \
+  CLIB_MEMORY_STORE_BARRIER();                          \
+  h = tmp;                                              \
+  tmp = tmp2;                                           \
+  clib_spinlock_unlock_if_init(&l);                     \
+} while(0);
+
+/** @brief call the specified callback set
+ * @param h the callback set
+ * @param varargs additional callback parameters
+ */
+#define clib_call_callbacks(h, ... )                    \
+do {                                                    \
+  /*                                                    \
+   * Note: fp exists to shut up gcc-6, which            \
+   * produces a warning not seen with gcc-7 or 8        \
+   */                                                   \
+  void (*fp)(void *a1, ...);                            \
+  int i;                                                \
+  for (i = 0; i < vec_len (h); i++)                     \
+    {                                                   \
+      fp = (void *)(h[i]);                              \
+      (*fp) (__VA_ARGS__);                              \
+    }                                                   \
+ } while (0);
+
+/** @brief predicate function says whether the specified function is enabled
+ * @param h the callback set
+ * @param l clib_spinlock_t lock to protect the vector, may be 0
+ * @param f the function to search for
+ * @return 1 if the function is enabled, 0 if not
+ */
+#define clib_callback_is_set(h,l,f)             \
+({                                              \
+  int _i;                                       \
+  int _found = 0;                               \
+  clib_spinlock_lock_if_init(&l);               \
+  for (_i = 0; _i < vec_len (h); _i++)          \
+    if (((void *)h[_i]) == (void *) f)          \
+      {                                         \
+        _found=1;                               \
+        break;                                  \
+      }                                         \
+  clib_spinlock_unlock_if_init(&l);             \
+  _found;                                       \
+ })
+
+#endif /* included_callback_h */
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */