[Lldb-commits] [lldb] b15b142 - [lldb/test] Don't use preexec_fn for launching inferiors
Pavel Labath via lldb-commits
lldb-commits at lists.llvm.org
Fri Jul 1 05:44:39 PDT 2022
Author: Pavel Labath
Date: 2022-07-01T14:36:01+02:00
New Revision: b15b1421bc9a11b318b65b489e5fd58dd917db1f
URL: https://github.com/llvm/llvm-project/commit/b15b1421bc9a11b318b65b489e5fd58dd917db1f
DIFF: https://github.com/llvm/llvm-project/commit/b15b1421bc9a11b318b65b489e5fd58dd917db1f.diff
LOG: [lldb/test] Don't use preexec_fn for launching inferiors
As the documentation states, using this is not safe in multithreaded
programs, and I have traced it to a rare deadlock in some of the tests.
The reason this was introduced was to be able to attach to a program
from the very first instruction, where our usual mechanism of
synchronization -- waiting for a file to appear -- does not work.
However, this is only needed for a single test
(TestGdbRemoteAttachWait) so instead of doing this everywhere, I create
a bespoke solution for that single test. The solution basically
consists of outsourcing the preexec_fn code to a separate (and
single-threaded) shim process, which enables attaching and then executes
the real program.
This pattern could be generalized in case we needed to use it for other
tests, but I suspect that we will not be having many tests like this.
This effectively reverts commit
a997a1d7fbe229433fb458bb0035b32424ecf3bd.
Added:
lldb/test/API/tools/lldb-server/attach-wait/Makefile
lldb/test/API/tools/lldb-server/attach-wait/TestGdbRemoteAttachWait.py
lldb/test/API/tools/lldb-server/attach-wait/main.cpp
lldb/test/API/tools/lldb-server/attach-wait/shim.cpp
Modified:
lldb/packages/Python/lldbsuite/test/lldbplatformutil.py
lldb/packages/Python/lldbsuite/test/lldbtest.py
Removed:
lldb/test/API/tools/lldb-server/TestGdbRemoteAttachWait.py
################################################################################
diff --git a/lldb/packages/Python/lldbsuite/test/lldbplatformutil.py b/lldb/packages/Python/lldbsuite/test/lldbplatformutil.py
index e14c4f8c0d38..719131c9248e 100644
--- a/lldb/packages/Python/lldbsuite/test/lldbplatformutil.py
+++ b/lldb/packages/Python/lldbsuite/test/lldbplatformutil.py
@@ -4,12 +4,11 @@
from __future__ import absolute_import
# System modules
-import ctypes
import itertools
-import os
import re
import subprocess
import sys
+import os
# Third-party modules
import six
@@ -192,14 +191,3 @@ def hasChattyStderr(test_case):
if match_android_device(test_case.getArchitecture(), ['aarch64'], range(22, 25+1)):
return True # The dynamic linker on the device will complain about unknown DT entries
return False
-
-if getHostPlatform() == "linux":
- def enable_attach():
- """Enable attaching to _this_ process, if host requires such an action.
- Suitable for use as a preexec_fn in subprocess.Popen and similar."""
- c = ctypes.CDLL(None)
- PR_SET_PTRACER = ctypes.c_int(0x59616d61)
- PR_SET_PTRACER_ANY = ctypes.c_ulong(-1)
- c.prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY)
-else:
- enable_attach = None
diff --git a/lldb/packages/Python/lldbsuite/test/lldbtest.py b/lldb/packages/Python/lldbsuite/test/lldbtest.py
index 22851730153e..d46e54f30bd5 100644
--- a/lldb/packages/Python/lldbsuite/test/lldbtest.py
+++ b/lldb/packages/Python/lldbsuite/test/lldbtest.py
@@ -393,7 +393,6 @@ def launch(self, executable, args, extra_env):
stdout=open(
os.devnull) if not self._trace_on else None,
stdin=PIPE,
- preexec_fn=lldbplatformutil.enable_attach,
env=env)
def terminate(self):
diff --git a/lldb/test/API/tools/lldb-server/attach-wait/Makefile b/lldb/test/API/tools/lldb-server/attach-wait/Makefile
new file mode 100644
index 000000000000..22f1051530f8
--- /dev/null
+++ b/lldb/test/API/tools/lldb-server/attach-wait/Makefile
@@ -0,0 +1 @@
+include Makefile.rules
diff --git a/lldb/test/API/tools/lldb-server/TestGdbRemoteAttachWait.py b/lldb/test/API/tools/lldb-server/attach-wait/TestGdbRemoteAttachWait.py
similarity index 80%
rename from lldb/test/API/tools/lldb-server/TestGdbRemoteAttachWait.py
rename to lldb/test/API/tools/lldb-server/attach-wait/TestGdbRemoteAttachWait.py
index ed31b5645c33..abcc98d22090 100644
--- a/lldb/test/API/tools/lldb-server/TestGdbRemoteAttachWait.py
+++ b/lldb/test/API/tools/lldb-server/attach-wait/TestGdbRemoteAttachWait.py
@@ -14,10 +14,12 @@ class TestGdbRemoteAttachWait(gdbremote_testcase.GdbRemoteTestCaseBase):
@skipIfWindows # This test is flaky on Windows
def test_attach_with_vAttachWait(self):
exe = '%s_%d' % (self.testMethodName, os.getpid())
+ exe_to_attach = exe
+ args = []
def launch_inferior():
inferior = self.launch_process_for_attach(
- inferior_args=["sleep:60"],
+ inferior_args=args,
exe_path=self.getBuildArtifact(exe))
self.assertIsNotNone(inferior)
self.assertTrue(inferior.pid > 0)
@@ -26,7 +28,14 @@ def launch_inferior():
inferior.pid, True))
return inferior
- self.build(dictionary={'EXE': exe})
+ self.build(dictionary={'EXE': exe, 'CXX_SOURCES': 'main.cpp'})
+ if self.getPlatform() != "windows":
+ # Use a shim to ensure that the process is ready to be attached from
+ # the get-go.
+ args = [self.getBuildArtifact(exe)]
+ exe = "shim"
+ self.build(dictionary={'EXE': exe, 'CXX_SOURCES': 'shim.cpp'})
+
self.set_inferior_startup_attach_manually()
server = self.connect_to_debug_monitor()
@@ -38,7 +47,8 @@ def launch_inferior():
self.do_handshake()
self.test_sequence.add_log_lines([
# Do the attach.
- "read packet: $vAttachWait;{}#00".format(lldbgdbserverutils.gdbremote_hex_encode_string(exe)),
+ "read packet: $vAttachWait;{}#00".format(
+ lldbgdbserverutils.gdbremote_hex_encode_string(exe_to_attach)),
], True)
# Run the stream until attachWait.
context = self.expect_gdbremote_sequence()
diff --git a/lldb/test/API/tools/lldb-server/attach-wait/main.cpp b/lldb/test/API/tools/lldb-server/attach-wait/main.cpp
new file mode 100644
index 000000000000..891dc9f5e7d1
--- /dev/null
+++ b/lldb/test/API/tools/lldb-server/attach-wait/main.cpp
@@ -0,0 +1,8 @@
+#include <thread>
+
+int main()
+{
+ // Wait to be attached.
+ std::this_thread::sleep_for(std::chrono::minutes(1));
+ return 0;
+}
diff --git a/lldb/test/API/tools/lldb-server/attach-wait/shim.cpp b/lldb/test/API/tools/lldb-server/attach-wait/shim.cpp
new file mode 100644
index 000000000000..33d75b195762
--- /dev/null
+++ b/lldb/test/API/tools/lldb-server/attach-wait/shim.cpp
@@ -0,0 +1,9 @@
+#include <unistd.h>
+#include <cstdio>
+
+int main(int argc, char *argv[]) {
+ lldb_enable_attach();
+ execlp(argv[1], argv[1], nullptr);
+ perror("execlp");
+ return 1;
+}
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