On Mon, Feb 2, 2015 at 10:46 PM, Victor Stinner <victor.stin...@gmail.com> wrote:
> 2015-02-02 22:11 GMT+01:00 Giampaolo Rodola' <g.rod...@gmail.com>: > > I may be chiming in a little late, however, I'd have a question: does > this > > affect non-blocking applications somehow? > > How often should we expect to receive EINTR? > > Each time a program is interrupted by a signal while it was waiting > for a sycall. Most syscalls are fast, especially in an application > written with non blocking operations. > > For example, timeit says that os.getuid() takes 370 nanoseconds (on > Linux). getpid() only takes 285 nanoseconds, but it looks to be cached > in the libc: strace doesn't show me syscalls. > > Network syscalls are probably slower. > > haypo@selma$ ./python -Wignore -m timeit -s 'import socket; > s,c=socket.socketpair()' 's.send(b"a"); c.recv(1)' > 100000 loops, best of 3: 2.26 usec per loop > > > Is it correct to state that in case many EINTR signals are sent > > repeatedly a non-blocking framework such as asyncio may hang for "too > long"? > > A syscall fails with EINTR each time it gets a signal. You are > unlikely if the same syscall requires to be retried twice (executed 3 > times) because it got EINTR twice. > > I don't see why the kernel would make a syscall fails EINTR multiple times. > > asyncio doesn't process the signal immediatly. asyncio uses > signal.set_wakeup_fd(). At the C level, the C signal handler writes > the signal number into a pipe. At the Python level, the selector is > awaken by the write. Later, asyncio executes the Python handler of the > signal (if a Python signal handler was registered). > > A nice side effect of the PEP is to avoid to awake the application if > it's not necessary. If no Python signal handler is registered, no byte > is written into the pipe, the selector continues to wait for events. > > Victor > OK, thanks for clarifying, this is a very nice addition. One last thing: should InterruptedError exception be deprecated? As far as I understand it should never occur again, right? -- Giampaolo - http://grodola.blogspot.com
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