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From cf4c740974834b7d5c9dc7b12a69c5269b0d7a2d Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Ond=C5=99ej=20Lyson=C4=9Bk?= <olysonek@redhat.com>
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Date: Thu, 24 Jan 2019 21:55:16 +0100
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Subject: [PATCH] procfs: Fix removing vanished processes in
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pidstats.reload_threads()
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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If a process disappears while iterating the loop in
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pidstats.reload_threads(), we get a RuntimeError as shown below. This
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is because we cannot remove an entry from a dictionary while iterating the
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dictionary.
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Reproducer:
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1. Add the following line to the beginning of pidstats.reload_threads():
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import pdb; pdb.set_trace()
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2. Start some process
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3. Start the python interpreter and proceed as follows:
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[~/git/python-linux-procfs]$ python3
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Python 3.6.8 (default, Jan 3 2019, 16:11:14)
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[GCC 8.2.1 20181215 (Red Hat 8.2.1-6)] on linux
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Type "help", "copyright", "credits" or "license" for more information.
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>>> import procfs
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>>> ps = procfs.pidstats()
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>>> ps.reload_threads()
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> /home/olysonek/git/python-linux-procfs/procfs/procfs.py(462)reload_threads()
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-> for pid in self.processes.keys():
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(Pdb) next
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> /home/olysonek/git/python-linux-procfs/procfs/procfs.py(463)reload_threads()
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-> try:
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At this point, terminate the process started in step 2. Return to the
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python interpreter:
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(Pdb) continue
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Traceback (most recent call last):
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File "<stdin>", line 1, in <module>
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File "/home/olysonek/git/python-linux-procfs/procfs/procfs.py", line 463, in reload_threads
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try:
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RuntimeError: dictionary changed size during iteration
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Signed-off-by: Ondřej Lysoněk <olysonek@redhat.com>
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Signed-off-by: John Kacur <jkacur@redhat.com>
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---
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procfs/procfs.py | 5 ++++-
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1 file changed, 4 insertions(+), 1 deletion(-)
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diff --git a/procfs/procfs.py b/procfs/procfs.py
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index c6f65890d0e4..b0ce2514063d 100755
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--- a/procfs/procfs.py
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+++ b/procfs/procfs.py
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@@ -459,12 +459,15 @@ class pidstats:
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self.processes[pid] = process(pid, self.basedir)
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def reload_threads(self):
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+ to_remove = []
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for pid in self.processes.keys():
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try:
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self.processes[pid].load_threads()
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except OSError:
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# process vanished, remove it
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- del self.processes[pid]
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+ to_remove.append(pid)
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+ for pid in to_remove:
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+ del self.processes[pid]
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def find_by_name(self, name):
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name = name[:15]
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--
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2.20.1
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