Info

ConnectBG handles asynchronous connects by spinning up a background thread to call ::connect(). We kick that thread out of connect, after a timeout, by calling close. This isn't safe because: Thread A: Your call to Socket::connect() Thread B: BG connector for A Thread C: Unrelated thread calling Socket::connect() Thread D: BG connector for C Thread A Thread B Thread C Thread D Start Thread B connect(N) Wait 4.9999 seconds get EINTR Trigger timeout shutdown(N) close(N) N = socket() connect(N) connect(N) errno == EISCONN Which can lead us to connect a fd to the wrong endpoint. We can work around this by only calling shutdown from the parent thread, waiting for the child to join, then calling close.

Top User Comments

xgen-internal-githook commented on Thu, 8 Dec 2016 19:14:36 +0000: Author: {u'username': u'hanumantmk', u'name': u'Jason Carey', u'email': u'jcarey@argv.me'} Message: SERVER-27240 Replace ConnectBG with poll It's unsafe to close a socket from another thread. Also, after returning EINTR, the connect call converts to an async call. And on non-linux systems that requires a fallback to poll/select to handle errors. Because of that, let's just do the connect without the background thread at all, starting off with poll. (cherry picked from commit a1baabeee5694aa8c4ffa1827233684d6c7fcc49) Branch: v3.0 https://github.com/mongodb/mongo/commit/80775cd49db61ec792313da630158a2904faa75f xgen-internal-githook commented on Thu, 8 Dec 2016 16:57:09 +0000: Author: {u'username': u'hanumantmk', u'name': u'Jason Carey', u'email': u'jcarey@argv.me'} Message: SERVER-27240 Replace ConnectBG with poll It's unsafe to close a socket from another thread. Also, after returning EINTR, the connect call converts to an async call. And on non-linux systems that requires a fallback to poll/select to handle errors. Because of that, let's just do the connect without the background thread at all, starting off with poll. (cherry picked from commit a1baabeee5694aa8c4ffa1827233684d6c7fcc49) Branch: v3.2 https://github.com/mongodb/mongo/commit/30e9f786ee94166adc1b6b3ba98b672d47604f95 xgen-internal-githook commented on Thu, 8 Dec 2016 16:50:53 +0000: Author: {u'username': u'hanumantmk', u'name': u'Jason Carey', u'email': u'jcarey@argv.me'} Message: SERVER-27240 Replace ConnectBG with poll It's unsafe to close a socket from another thread. Also, after returning EINTR, the connect call converts to an async call. And on non-linux systems that requires a fallback to poll/select to handle errors. Because of that, let's just do the connect without the background thread at all, starting off with poll. (cherry picked from commit a1baabeee5694aa8c4ffa1827233684d6c7fcc49) Branch: v3.4 https://github.com/mongodb/mongo/commit/e4113518e7b0f9dcdfe582d91f4f00dcc0589661 xgen-internal-githook commented on Wed, 7 Dec 2016 20:58:30 +0000: Author: {u'username': u'hanumantmk', u'name': u'Jason Carey', u'email': u'jcarey@argv.me'} Message: SERVER-27240 Replace ConnectBG with poll It's unsafe to close a socket from another thread. Also, after returning EINTR, the connect call converts to an async call. And on non-linux systems that requires a fallback to poll/select to handle errors. Because of that, let's just do the connect without the background thread at all, starting off with poll. Branch: master https://github.com/mongodb/mongo/commit/a1baabeee5694aa8c4ffa1827233684d6c7fcc49

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