Fixes SIGSEGV and improve thread safety of journal.Reader class#144
Fixes SIGSEGV and improve thread safety of journal.Reader class#144sebres wants to merge 4 commits into
Conversation
Sorry, something went wrong.
…th ref-counter; avoid segfault by closing journal across threads (closes systemdgh-143)
…ids unexpected states on repeated Reader.close)
sebres
force-pushed
the
gh-143-sf-fix
branch
2 times, most recently
from
5a7719b to
03eec9d
Compare
April 2, 2025 16:31
|
7c99a39 seems to fix the GHA flows now (completely different issue), so can be cherry-picked to main branch as it is (or I could make a separate PR if necessary). |
Sorry, something went wrong.
|
Ping. |
Sorry, something went wrong.
|
The PR #147 will help fix the GH Action headache for this PR. |
Sorry, something went wrong.
Hmm... There is basically no problem to fix "for this PR" - as you can see all GHA checks are passed. |
Sorry, something went wrong.
This PR fixes threaded issues of journal.Reader class and improves its thread-safety, using simple protection with ref-counter;
It would avoid segfault by closing journal across threads.
The algorithm is simple, here short explanation illustrating the approach on an example of #143:
Reader_wait(), increment ref-count, release the lock (GIL), entersd_journal_wait()sd_journal_wait(), acquiring the lock (GIL), decrement ref-count, not callingsd_journal_close()because ofref_count == 1, leaveReader_wait()wait()however thread B invokesclose()in-between ...Reader_wait(), increment ref-count, release the lock (GIL), entersd_journal_wait()Reader_close(), set closed flag, decrement ref-count, but don't close it because ofref_count > 0sd_journal_wait(), acquiring the lock (GIL), decrement ref-count, callingsd_journal_close()because ofref_count == 0, leaveReader_wait()If thread B manages to close the handle before A enters wait mode, it is also safe, because then
sd_journal_wait()would generate EINVARG andReader.wait()raises an error ([Errno 22] Invalid argument).Anyway, no segfault happens anymore and it is more or less thread-safe.
closes gh-143