diff options
| -rw-r--r-- | buildstream/_signals.py | 66 |
1 files changed, 34 insertions, 32 deletions
diff --git a/buildstream/_signals.py b/buildstream/_signals.py index 2154221b4..df79f6340 100644 --- a/buildstream/_signals.py +++ b/buildstream/_signals.py @@ -30,12 +30,6 @@ terminator_stack = deque() suspendable_stack = deque() -class Suspender(): - def __init__(self, suspend_callback, resume_callback): - self.suspend = suspend_callback - self.resume = resume_callback - - # Per process SIGTERM handler def terminator_handler(signal, frame): while terminator_stack: @@ -47,25 +41,6 @@ def terminator_handler(signal, frame): os._exit(-1) -# Per process SIGTSTP handler -def suspend_handler(sig, frame): - - # Suspend callbacks from innermost frame first - for suspender in reversed(suspendable_stack): - suspender.suspend() - - # Use SIGSTOP directly now, dont introduce more SIGTSTP - os.kill(os.getpid(), signal.SIGSTOP) - - -# Per process SIGCONT handler -def resume_handler(sig, frame): - - # Resume callbacks from outermost frame inwards - for suspender in suspendable_stack: - suspender.resume() - - # terminator() # # A context manager for interruptable tasks, this guarantees @@ -93,14 +68,43 @@ def terminator(terminate_func): terminator_stack.pop() +# Just a simple object for holding on to two callbacks +class Suspender(): + def __init__(self, suspend_callback, resume_callback): + self.suspend = suspend_callback + self.resume = resume_callback + + +# Per process SIGTSTP handler +def suspend_handler(sig, frame): + + # Suspend callbacks from innermost frame first + for suspender in reversed(suspendable_stack): + suspender.suspend() + + # Use SIGSTOP directly now on self, dont introduce more SIGTSTP + # + # Here the process sleeps until SIGCONT, which we simply + # dont handle. We know we'll pickup execution right here + # when we wake up. + os.kill(os.getpid(), signal.SIGSTOP) + + # Resume callbacks from outermost frame inwards + for suspender in suspendable_stack: + suspender.resume() + + # suspendable() # -# A context manager for a code block which spawns a process -# that becomes its own session leader. +# A context manager for handling process suspending and resumeing +# +# This must be used in code blocks which spawn processes that become +# their own session leader. In these cases, SIGSTOP and SIGCONT need +# to be propagated to the child process group. # -# In these cases, SIGSTOP and SIGCONT need to be propagated to -# the child tasks, this is not expected to be used recursively, -# as the codeblock is expected to just spawn a processes. +# This context manager can also be used recursively, so multiple +# things can happen at suspend/resume time (such as tracking timers +# and ensuring durations do not count suspended time). # @contextmanager def suspendable(suspend_callback, resume_callback): @@ -111,13 +115,11 @@ def suspendable(suspend_callback, resume_callback): suspendable_stack.append(suspender) if outermost: - original_cont = signal.signal(signal.SIGCONT, resume_handler) original_stop = signal.signal(signal.SIGTSTP, suspend_handler) yield if outermost: signal.signal(signal.SIGTSTP, original_stop) - signal.signal(signal.SIGCONT, original_cont) suspendable_stack.pop() |