[v3,2/2,gdb/dap] Fix stray KeyboardInterrupt after cancel
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Commit Message
When running test-case gdb.dap/pause.exp 100 times in a loop, it passes
100/100.
But if we remove the two "sleep 0.2" from the test-case, we run into
(copied from dap.log and edited for readability):
...
Traceback (most recent call last):
File "startup.py", line 251, in message
def message():
KeyboardInterrupt
Quit
...
This happens as follows.
CancellationHandler.cancel calls gdb.interrupt to cancel a request in flight.
The idea is that this interrupt triggers while in fn here in message (a nested
function of send_gdb_with_response):
...
def message():
try:
val = fn()
result_q.put(val)
except (Exception, KeyboardInterrupt) as e:
result_q.put(e)
...
but instead it triggers outside the try/except.
Fix this by:
- in CancellationHandler, renaming variable in_flight to in_flight_dap_thread,
and adding a variable in_flight_gdb_thread to be able to distinguish when
a request is in flight in the dap thread or the gdb thread.
- adding a wrapper Cancellable to to deal with cancelling the wrapped
event
- using Cancellable in send_gdb and send_gdb_with_response to wrap the posted
event
- in CancellationHandler.cancel, only call gdb.interrupt if
req == self.in_flight_gdb_thread.
This makes the test-case pass 100/100, also when adding the extra stressor of
"taskset -c 0", which makes the fail more likely without the patch.
Tested on aarch64-linux.
PR dap/31275
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31275
---
gdb/python/lib/gdb/dap/server.py | 88 ++++++++++++++++++++++++--------
gdb/testsuite/gdb.dap/pause.exp | 4 +-
2 files changed, 69 insertions(+), 23 deletions(-)
Comments
>>>>> "Tom" == Tom de Vries <tdevries@suse.de> writes:
Tom> # Wait a little to try to ensure the command is running.
Tom> -sleep 0.2
Tom> +#sleep 0.2
Tom> set cancel_id [dap_send_request cancel \
Tom> [format {o requestId [i %d]} $cont_id]]
Tom> @@ -140,7 +140,7 @@ set cont_id [dap_send_request evaluate \
Tom> $gdbfile]]
Tom> # Wait a little to try to ensure the command is running.
Tom> -sleep 0.2
Tom> +#sleep 0.2
Tom> set cancel_id [dap_send_request cancel \
Tom> [format {o requestId [i %d]} $cont_id]]
These hunks should probably be dropped.
Ok with that change.
Approved-By: Tom Tromey <tom@tromey.com>
Tom
@@ -19,6 +19,7 @@ import heapq
import inspect
import json
import threading
+from contextlib import contextmanager
from .io import start_json_writer, read_json
from .startup import (
@@ -59,24 +60,19 @@ class CancellationHandler:
# Methods on this class acquire this lock before proceeding.
self.lock = threading.Lock()
# The request currently being handled, or None.
- self.in_flight = None
+ self.in_flight_dap_thread = None
+ self.in_flight_gdb_thread = None
self.reqs = []
def starting(self, req):
- """Call at the start of the given request.
-
- Throws the appropriate exception if the request should be
- immediately cancelled."""
+ """Call at the start of the given request."""
with self.lock:
- self.in_flight = req
- while len(self.reqs) > 0 and self.reqs[0] <= req:
- if heapq.heappop(self.reqs) == req:
- raise KeyboardInterrupt()
+ self.in_flight_dap_thread = req
def done(self, req):
"""Indicate that the request is done."""
with self.lock:
- self.in_flight = None
+ self.in_flight_dap_thread = None
def cancel(self, req):
"""Call to cancel a request.
@@ -85,7 +81,7 @@ class CancellationHandler:
If the request is in flight, it is interrupted.
If the request has not yet been seen, the cancellation is queued."""
with self.lock:
- if req == self.in_flight:
+ if req == self.in_flight_gdb_thread:
gdb.interrupt()
else:
# We don't actually ignore the request here, but in
@@ -96,6 +92,29 @@ class CancellationHandler:
# to try to check for this.
heapq.heappush(self.reqs, req)
+ @contextmanager
+ def interruptable_region(self, req):
+ """Return a new context manager that sets in_flight_gdb_thread to
+ REQ."""
+ if req is None:
+ # No request is handled in the region, just execute the region.
+ yield
+ return
+ try:
+ with self.lock:
+ # If the request is cancelled, don't execute the region.
+ while len(self.reqs) > 0 and self.reqs[0] <= req:
+ if heapq.heappop(self.reqs) == req:
+ raise KeyboardInterrupt()
+ # Request is being handled by the gdb thread.
+ self.in_flight_gdb_thread = req
+ # Execute region. This may be interrupted by gdb.interrupt.
+ yield
+ finally:
+ with self.lock:
+ # Request is no longer handled by the gdb thread.
+ self.in_flight_gdb_thread = None
+
class Server:
"""The DAP server class."""
@@ -434,13 +453,45 @@ class Invoker(object):
exec_and_log(self.cmd)
+class Cancellable(object):
+
+ def __init__(self, fn, result_q=None):
+ self.fn = fn
+ self.result_q = result_q
+ with _server.canceller.lock:
+ self.req = _server.canceller.in_flight_dap_thread
+
+ # This is invoked in the gdb thread to run self.fn.
+ @in_gdb_thread
+ def __call__(self):
+ try:
+ with _server.canceller.interruptable_region(self.req):
+ val = self.fn()
+ if self.result_q is not None:
+ self.result_q.put(val)
+ except (Exception, KeyboardInterrupt) as e:
+ if self.result_q is not None:
+ # Pass result or exception to caller.
+ self.result_q.put(e)
+ elif isinstance(e, KeyboardInterrupt):
+ # Fn was cancelled.
+ pass
+ else:
+ # Exception happened. Ignore and log it.
+ err_string = "%s, %s" % (err, type(err))
+ thread_log("caught exception: " + err_string)
+ log_stack()
+
+
def send_gdb(cmd):
"""Send CMD to the gdb thread.
CMD can be either a function or a string.
If it is a string, it is passed to gdb.execute."""
if isinstance(cmd, str):
cmd = Invoker(cmd)
- gdb.post_event(cmd)
+
+ # Post the event and don't wait for the result.
+ gdb.post_event(Cancellable(cmd))
def send_gdb_with_response(fn):
@@ -452,17 +503,12 @@ def send_gdb_with_response(fn):
"""
if isinstance(fn, str):
fn = Invoker(fn)
- result_q = DAPQueue()
- def message():
- try:
- val = fn()
- result_q.put(val)
- except (Exception, KeyboardInterrupt) as e:
- result_q.put(e)
-
- send_gdb(message)
+ # Post the event and wait for the result in result_q.
+ result_q = DAPQueue()
+ gdb.post_event(Cancellable(fn, result_q))
val = result_q.get()
+
if isinstance(val, (Exception, KeyboardInterrupt)):
raise val
return val
@@ -119,7 +119,7 @@ set cont_id [dap_send_request evaluate \
$gdbfile]]
# Wait a little to try to ensure the command is running.
-sleep 0.2
+#sleep 0.2
set cancel_id [dap_send_request cancel \
[format {o requestId [i %d]} $cont_id]]
@@ -140,7 +140,7 @@ set cont_id [dap_send_request evaluate \
$gdbfile]]
# Wait a little to try to ensure the command is running.
-sleep 0.2
+#sleep 0.2
set cancel_id [dap_send_request cancel \
[format {o requestId [i %d]} $cont_id]]