test: hook into PID in tracing tests

This makes sure to NOT hook into other bitcoind binaries run in
paralell in the test framework. We only want to trace the intended
binary.

In interface_usdt_utxocache.py:
While testing the utxocache flush with pruning, bitcoind is
restarted and we need to hook into the new PID again.

Author: 0xB10C

test/functional/interface_usdt_net.py

@@ -109,7 +109,7 @@ def __repr__(self):
 
         self.log.info(
             "hook into the net:inbound_message and net:outbound_message tracepoints")
-        ctx = USDT(path=str(self.options.bitcoind))
+        ctx = USDT(pid=self.nodes[0].process.pid)
         ctx.enable_probe(probe="net:inbound_message",
                          fn_name="trace_inbound_message")
         ctx.enable_probe(probe="net:outbound_message",

test/functional/interface_usdt_utxocache.py

@@ -173,7 +173,7 @@ def test_uncache(self):
         invalid_tx.vin[0].prevout.hash = int(block_1_coinbase_txid, 16)
 
         self.log.info("hooking into the utxocache:uncache tracepoint")
-        ctx = USDT(path=str(self.options.bitcoind))
+        ctx = USDT(pid=self.nodes[0].process.pid)
         ctx.enable_probe(probe="utxocache:uncache",
                          fn_name="trace_utxocache_uncache")
         bpf = BPF(text=utxocache_changes_program, usdt_contexts=[ctx], debug=0)
@@ -238,7 +238,7 @@ def test_add_spent(self):
 
         self.log.info(
             "hook into the utxocache:add and utxocache:spent tracepoints")
-        ctx = USDT(path=str(self.options.bitcoind))
+        ctx = USDT(pid=self.nodes[0].process.pid)
         ctx.enable_probe(probe="utxocache:add", fn_name="trace_utxocache_add")
         ctx.enable_probe(probe="utxocache:spent",
                          fn_name="trace_utxocache_spent")
@@ -334,7 +334,7 @@ def test_flush(self):
 
         self.log.info("test the utxocache:flush tracepoint API")
         self.log.info("hook into the utxocache:flush tracepoint")
-        ctx = USDT(path=str(self.options.bitcoind))
+        ctx = USDT(pid=self.nodes[0].process.pid)
         ctx.enable_probe(probe="utxocache:flush",
                          fn_name="trace_utxocache_flush")
         bpf = BPF(text=utxocache_flushes_program, usdt_contexts=[ctx], debug=0)
@@ -373,6 +373,7 @@ def handle_utxocache_flush(_, data, __):
         self.stop_node(0)
 
         bpf.perf_buffer_poll(timeout=200)
+        bpf.cleanup()
 
         self.log.info("check that we don't expect additional flushes")
         assert_equal(0, len(expected_flushes))
@@ -381,6 +382,14 @@ def handle_utxocache_flush(_, data, __):
         self.log.info("restart the node with -prune")
         self.start_node(0, ["-fastprune=1", "-prune=1"])
 
+        self.log.info("test the utxocache:flush tracepoint API with pruning")
+        self.log.info("hook into the utxocache:flush tracepoint")
+        ctx = USDT(pid=self.nodes[0].process.pid)
+        ctx.enable_probe(probe="utxocache:flush",
+                         fn_name="trace_utxocache_flush")
+        bpf = BPF(text=utxocache_flushes_program, usdt_contexts=[ctx], debug=0)
+        bpf["utxocache_flush"].open_perf_buffer(handle_utxocache_flush)
+
         BLOCKS_TO_MINE = 350
         self.log.info(f"mine {BLOCKS_TO_MINE} blocks to be able to prune")
         self.generate(self.wallet, BLOCKS_TO_MINE)

test/functional/interface_usdt_validation.py

@@ -94,7 +94,7 @@ def __repr__(self):
         expected_blocks = list()
 
         self.log.info("hook into the validation:block_connected tracepoint")
-        ctx = USDT(path=str(self.options.bitcoind))
+        ctx = USDT(pid=self.nodes[0].process.pid)
         ctx.enable_probe(probe="validation:block_connected",
                          fn_name="trace_block_connected")
         bpf = BPF(text=validation_blockconnected_program,