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https://issues.apache.org/jira/browse/PROTON-1727?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16301675#comment-16301675
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ASF subversion and git services commented on PROTON-1727:
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Commit 223e6d012dab8bbe4bdb92538d84c630bbd1cf27 in qpid-proton's branch
refs/heads/master from [~aconway]
[ https://git-wip-us.apache.org/repos/asf?p=qpid-proton.git;h=223e6d0 ]
PROTON-1727 [epoll] fix race condition
Needed to set current_arm flag on second and subsequent connect attempts when
resolve returns multiple socket addresses. Otherwise another thread can delete
the connection early.
> [epoll proactor] segfaults, hangs and leaked FDs around failed connect
> ----------------------------------------------------------------------
>
> Key: PROTON-1727
> URL: https://issues.apache.org/jira/browse/PROTON-1727
> Project: Qpid Proton
> Issue Type: Bug
> Components: proton-c
> Affects Versions: proton-c-0.18.1
> Reporter: Alan Conway
> Assignee: Alan Conway
> Priority: Blocker
> Fix For: proton-c-0.20.0
>
>
> There is a race condition that causes leaked FDs and segfaults in the epoll
> proactor under the following conditions:
> - there is more than one thread processing proactor events.
> - attempting to connect to a host address that resolves to multiple socket
> addresses, e.g. resolving the NULL hostname on a machine with ipv4 and ipv6
> enabled.
> - there is nothing listening on the target port.
> The attached reproducer shows several bad behaviors:
> - under rr or valgrind (--tool=memcheck and --tool=helgrind) it quickly (<
> 1min) shows race conditions and/or invalid memory access.
> - it hangs fairly often even without valgrind/rr, more so if you increase the
> thread count. Without valgrind/rr it rarely segfaults.
> - it leaks FDs - the test should run forever, but runs out of FDs around 1024
> iterations.
> This is probably the cause of
> https://issues.apache.org/jira/browse/DISPATCH-902, which does occur very
> frequently under the conditions described there.
> The test program should run forever without leaking or showing any faults.
> Note that gcc -fsantize does not detect races or memory errors, which
> suggests the bug requires a delay at the right time to manifest. Valgrind's
> overhead and rr's code serialization appears to provide that delay. It seems
> likely that dispatch's reconnect logic is providing the delay in DISPATCH-902.
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