uv_poll_stop and uv_accept must happen on the same thread, so how are they racing? Once uv_poll_stop is called, it should be safe to notify another thread to call close, even if that then happens concurrently, as the kernel should be thread-safe (though weird things may happen in userspace if you close a fd that is concurrently in use on another thread or event queue).
On Sun, May 9, 2021 at 1:24 PM Paul Romero <pa...@rcom-software.com> wrote: > Hi: > > Using TSAN did turn up one very signifcant problem. The root cause of the > TCP socket descriptor corrpution > is that accept4() executes concurrently in the main() task, with close() > in the Protocol_Task(). > > As an interim measure I avoid the problem by simply not calling close(). > So far this has worked > seemlesly and Libuv appears to automatically free socket descriptors. The > Libuv documentation > about this is somewhat ambiguous. It indicates that after calling > uv_poll_stop() or uv_close(), > for a particular uv_poll_t poll handle, the socket descriptor is returned > to the user per the Libuv > contract. I am not sure what that means, and in particular, if it means > the socket descriptor is freed. > Can you clarify this ? > > A tagential issue is whether Linux accept4() and close() are thread safe. > I believe they > are and the crucial data is protected in the kernel. Is it possible Libuv > is not handling the accept4() > return codes correctly ? The Linux accept4() man page details how errors > should be handled and is it > somewhat fussy. The Linux close() man page also details error handling but > it is straight forward. > > Also, I haven't been able to make the program compiled with TSAN dump > core. Do you have > any suggestions ? Incidentally, I had to use clang rather than the usual > gcc to get > TSAN to work on my system. > > Best Regards, > > Paul R. > > On 05/08/2021 08:51 AM, Jameson Nash wrote: > > Are you still accessing libuv (sans explicitly thread-safe functions such > as uv_async_send) from multiple threads, as you mentioned earlier? If so, > I'd suggest fixing that first. In conjunction, I recommend running TSan and > making sure it runs cleanly before checking for library or logic problems. > Then, if it is still a rare failure, I recommend debugging under `rr` as > you'll be able to run forward to the problem, then walk backwards through > the code to see what happened to your state and file descriptors. > > > On Sat, May 8, 2021 at 11:27 AM pa...@rcom-software.com < > pa...@rcom-software.com> wrote: > >> Hi: >> >> Addition to my last message. When uv__nonblock() fails it is indicative >> of a Linux FIONBIO ioctl() failure. What would cause >> setting non-blocking mode to fail ? >> >> Best Regards, >> >> Paul R. >> > -- > You received this message because you are subscribed to the Google Groups > "libuv" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to libuv+unsubscr...@googlegroups.com. > To view this discussion on the web visit > <https://groups.google.com/d/msgid/libuv/CADnnjUW6KL3OQw5C54aNfKh95z1OpQiq2bgVtXya8z_BeqMS9w%40mail.gmail.com?utm_medium=email&utm_source=footer> > https://groups.google.com/d/msgid/libuv/CADnnjUW6KL3OQw5C54aNfKh95z1OpQiq2bgVtXya8z_BeqMS9w%40mail.gmail.com > . > > > -- > > > Paul Romero > ----------- > RCOM Communications Software > EMAIL: pa...@rcom-software.com > PHONE: (510)482-2769 > > > > > > -- > You received this message because you are subscribed to the Google Groups > "libuv" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to libuv+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/libuv/60981AE7.3000809%40rcom-software.com > <https://groups.google.com/d/msgid/libuv/60981AE7.3000809%40rcom-software.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "libuv" group. To unsubscribe from this group and stop receiving emails from it, send an email to libuv+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/libuv/CADnnjUVhyLDmxdxyyM5K1DL-%3DG6FK%3DY-OVE6ianUfpVC1AYeOQ%40mail.gmail.com.
