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4bcadd6686
Our SIGTSTP handler was working, but that was mostly accidental. The reason it worked is because lldb is multithreaded for most of its lifetime and the OS is reasonably fast at responding to signals. So, what happened was that the kill(SIGTSTP) which we sent from inside the handler was delivered to another thread while the handler was still set to SIG_DFL (which then correctly put the entire process to sleep). Sometimes it happened that the other thread got the second signal after the first thread had already restored the handler, in which case the signal handler would run again, and it would again attempt to send the SIGTSTP signal back to itself. Normally it didn't take many iterations for the signal to be delivered quickly enough. However, if you were unlucky (or were playing around with pexpect) you could get SIGTSTP while lldb was single-threaded, and in that case, lldb would go into an endless loop because the second SIGTSTP could only be handled on the main thread, and only after the handler for the first signal returned (and re-installed itself). In that situation the handler would keep re-sending the signal to itself. This patch fixes the issue by implementing the handler the way it supposed to be done: - before sending the second SIGTSTP, we unblock the signal (it gets automatically blocked upon entering the handler) - we use raise to send the signal, which makes sure it gets delivered to the thread which is running the handler This also means we don't need the SIGCONT handler, as our TSTP handler resumes right after the entire process is continued, and we can do the required work there. I also include a test case for the SIGTSTP flow. It uses pexpect, but it includes a couple of extra twists. Specifically, I needed to create an extra process on top of lldb, which will run lldb in a separate process group and simulate the role of the shell. This is needed because SIGTSTP is not effective on a session leader (the signal gets delivered, but it does not cause a stop) -- normally there isn't anyone to notice the stop. Differential Revision: https://reviews.llvm.org/D120320
86 lines
2.6 KiB
Python
86 lines
2.6 KiB
Python
from __future__ import absolute_import
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# System modules
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import os
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import sys
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# Third-party modules
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import six
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# LLDB Modules
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import lldb
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from .lldbtest import *
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from . import lldbutil
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from lldbsuite.test.decorators import *
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@skipIfRemote
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@skipIfWindows # llvm.org/pr22274: need a pexpect replacement for windows
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class PExpectTest(TestBase):
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NO_DEBUG_INFO_TESTCASE = True
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PROMPT = "(lldb) "
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def expect_prompt(self):
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self.child.expect_exact(self.PROMPT)
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def launch(self, executable=None, extra_args=None, timeout=60,
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dimensions=None, run_under=None, post_spawn=None):
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logfile = getattr(sys.stdout, 'buffer',
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sys.stdout) if self.TraceOn() else None
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args = []
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if run_under is not None:
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args += run_under
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args += [lldbtest_config.lldbExec, '--no-lldbinit', '--no-use-colors']
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for cmd in self.setUpCommands():
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args += ['-O', cmd]
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if executable is not None:
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args += ['--file', executable]
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if extra_args is not None:
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args.extend(extra_args)
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env = dict(os.environ)
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env["TERM"] = "vt100"
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env["HOME"] = self.getBuildDir()
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import pexpect
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self.child = pexpect.spawn(
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args[0], args=args[1:], logfile=logfile,
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timeout=timeout, dimensions=dimensions, env=env)
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if post_spawn is not None:
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post_spawn()
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self.expect_prompt()
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for cmd in self.setUpCommands():
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self.child.expect_exact(cmd)
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self.expect_prompt()
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if executable is not None:
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self.child.expect_exact("target create")
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self.child.expect_exact("Current executable set to")
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self.expect_prompt()
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def expect(self, cmd, substrs=None):
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self.assertNotIn('\n', cmd)
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# If 'substrs' is a string then this code would just check that every
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# character of the string is in the output.
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assert not isinstance(substrs, six.string_types), \
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"substrs must be a collection of strings"
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self.child.sendline(cmd)
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if substrs is not None:
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for s in substrs:
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self.child.expect_exact(s)
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self.expect_prompt()
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def quit(self, gracefully=True):
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self.child.sendeof()
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self.child.close(force=not gracefully)
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self.child = None
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def cursor_forward_escape_seq(self, chars_to_move):
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"""
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Returns the escape sequence to move the cursor forward/right
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by a certain amount of characters.
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"""
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return b"\x1b\[" + str(chars_to_move).encode("utf-8") + b"C"
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