[Lldb-commits] [PATCH] D58257: Disable ExecControl/StopHook/stop-hook-threads.test on Linux

[Jorge Gorbe Moya via Phabricator via lldb-commits]

jgorbe created this revision.
jgorbe added reviewers: labath, zturner.
Herald added a subscriber: jdoerfert.

ExecControl/StopHook/stop-hook-threads.test is flaky on Linux (it's consistently failing on my machine, but doesn't fail on a co-worker's). I'm seeing the following assertion failure:

  CommandObject.cpp:145: bool lldb_private::CommandObject::CheckRequirements(lldb_private::CommandReturnObject&): Assertion `m_exe_ctx.GetTargetPtr() == NULL' failed.

Interestingly, this doesn't happen when typing the same commands in interactive mode. The cause seems to be that, in synchronous execution mode `continue` waits until the process stops again, and that includes running any stop-hooks for that later stop, so we end with a stack trace like this (lots of frames omitted for clarity):

  abort()
  CommandObject::CheckRequirements() <-- this is again the same instance of CommandObjectProcessContinue, fails assertion because the previous continue command hasn't finished.
  Target::RunStopHooks()
  CommandObjectProcessContinue::DoExecute()
  Target::RunStopHooks()

In general, it seems like using process control commands inside stop-hooks does not have very well defined semantics. You don't even need multiple threads to make that assertion fail, you can build

  #include <cstdio>
  int main() {
    printf("1\n");  // break1
    printf("2\n");  // break2
  }

and then on lldb

  target stop-hook add -o continue
  break set -f stop-hook-simple.cpp -p "break1"
  break set -f stop-hook-simple.cpp -p "break2"
  run

In this case it's even worse because the presence of multiple threads makes it prone to race conditions. In some tests I ran with a simpler version of this test case, I was hitting either the previous assertion failure or the following issue:

1. Two threads reach a breakpoint
2. First stop-hook does a `process continue`
3. Threads end
4. Second stop-hook runs, complains about process not existing.

This change disables the test on Linux. It's already marked as XFAIL on Windows, so maybe we should just delete it until it's clear what should be the expected behavior in these cases. Or maybe try to come up with a way to write a similar multithreaded test without calling `continue` from a stop hook, I don't know.


https://reviews.llvm.org/D58257

Files:
  lldb/lit/ExecControl/StopHook/stop-hook-threads.test


Index: lldb/lit/ExecControl/StopHook/stop-hook-threads.test
===================================================================
--- lldb/lit/ExecControl/StopHook/stop-hook-threads.test
+++ lldb/lit/ExecControl/StopHook/stop-hook-threads.test
@@ -4,6 +4,7 @@
 # RUN: %lldb -b -s %p/Inputs/stop-hook-threads-2.lldbinit -s %s -f %t \
 # RUN:     | FileCheck --check-prefix=CHECK --check-prefix=CHECK-FILTER %s
 # XFAIL: system-windows
+# UNSUPPORTED: linux
 
 thread list
 break set -f stop-hook-threads.cpp -p "Set break point at this line"


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