mirror of https://github.com/python/cpython
ab4413a7e9
If we have a chain of generators/coroutines that are 'yield from'ing each other, then resuming the stack works like: - call send() on the outermost generator - this enters _PyEval_EvalFrameDefault, which re-executes the YIELD_FROM opcode - which calls send() on the next generator - which enters _PyEval_EvalFrameDefault, which re-executes the YIELD_FROM opcode - ...etc. However, every time we enter _PyEval_EvalFrameDefault, the first thing we do is to check for pending signals, and if there are any then we run the signal handler. And if it raises an exception, then we immediately propagate that exception *instead* of starting to execute bytecode. This means that e.g. a SIGINT at the wrong moment can "break the chain" – it can be raised in the middle of our yield from chain, with the bottom part of the stack abandoned for the garbage collector. The fix is pretty simple: there's already a special case in _PyEval_EvalFrameEx where it skips running signal handlers if the next opcode is SETUP_FINALLY. (I don't see how this accomplishes anything useful, but that's another story.) If we extend this check to also skip running signal handlers when the next opcode is YIELD_FROM, then that closes the hole – now the exception can only be raised at the innermost stack frame. This shouldn't have any performance implications, because the opcode check happens inside the "slow path" after we've already determined that there's a pending signal or something similar for us to process; the vast majority of the time this isn't true and the new check doesn't run at all. |
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| .. | ||
| ACKS | ||
| HISTORY | ||
| NEWS | ||
| Porting | ||
| README | ||
| README.AIX | ||
| README.coverity | ||
| README.valgrind | ||
| SpecialBuilds.txt | ||
| coverity_model.c | ||
| gdbinit | ||
| indent.pro | ||
| python-config.in | ||
| python-config.sh.in | ||
| python-wing3.wpr | ||
| python-wing4.wpr | ||
| python-wing5.wpr | ||
| python.man | ||
| python.pc.in | ||
| svnmap.txt | ||
| valgrind-python.supp | ||
| vgrindefs | ||
README
Python Misc subdirectory ======================== This directory contains files that wouldn't fit in elsewhere. Some documents are only of historic importance. Files found here ---------------- ACKS Acknowledgements gdbinit Handy stuff to put in your .gdbinit file, if you use gdb HISTORY News from previous releases -- oldest last indent.pro GNU indent profile approximating my C style NEWS News for this release (for some meaning of "this") Porting Mini-FAQ on porting to new platforms python-config.in Python script template for python-config python.man UNIX man page for the python interpreter python.pc.in Package configuration info template for pkg-config python-wing*.wpr Wing IDE project file README The file you're reading now README.AIX Information about using Python on AIX README.coverity Information about running Coverity's Prevent on Python README.valgrind Information for Valgrind users, see valgrind-python.supp SpecialBuilds.txt Describes extra symbols you can set for debug builds svnmap.txt Map of old SVN revs and branches to hg changeset ids valgrind-python.supp Valgrind suppression file, see README.valgrind vgrindefs Python configuration for vgrind (a generic pretty printer)