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Bug 1405071 - getaddrinfo looses internal lock with deferred cancellation.
Summary: getaddrinfo looses internal lock with deferred cancellation.
Keywords:
Status: CLOSED WONTFIX
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: glibc
Version: 7.0
Hardware: x86_64
OS: Linux
unspecified
unspecified
Target Milestone: pre-dev-freeze
: ---
Assignee: glibc team
QA Contact: qe-baseos-tools-bugs
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2016-12-15 14:09 UTC by Keyue Hu
Modified: 2019-06-18 19:34 UTC (History)
5 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed: 2019-06-18 19:34:34 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)
backtrace of deadlock (17.83 KB, text/plain)
2016-12-15 14:09 UTC, Keyue Hu 		no flags Details
View All


Links
System ID Private Priority Status Summary Last Updated
Sourceware 20975 0 P2 NEW Deferred cancellation triggers in __check_pf and looses lock leading to deadlock. 2020-06-05 12:43:52 UTC

Description Keyue Hu 2016-12-15 14:09:45 UTC 
Created attachment 1232178 [details]
backtrace of deadlock

Description of problem:
when pthread_cancel() on the thread calling getaddrinfo(), the libc lock in check_pf.c might be left without being unlocked. and then the next getaddrinfo call hangs forever. 


Version-Release number of selected component (if applicable):
glibc-2.17-106.el7_2.8.x86_64


How reproducible:
easy to reproduce.

Steps to Reproduce:
1. start thread calling zookeeper_init on 127.0.0.1 which calls getaddrinfo
2. call pthread_cancel on this thread
3. repeat 1-2

Actual results:
get hanged on getaddrinfo

Expected results:
never hangs


Additional info:
[root@3b3cfab6b378 /]# uname -a
Linux 3b3cfab6b378 3.10.0-327.36.3.el7.x86_64 #1 SMP Mon Oct 24 16:09:20 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
[root@3b3cfab6b378 /]# rpm -q glibc
glibc-2.17-106.el7_2.8.x86_64
Comment 1 Keyue Hu 2016-12-15 14:14:48 UTC 
in the source code of glibc, sysdeps/unix/sysv/linux/check_pf.c 

between L322-L356, there are pthread cancellation point in __socket, __bind, or make_request. If we get pthread_cancel, when code goes in L322-L356 the check_pf lock is left locked. 

by the way the upstream glibc seems has no such issue.
Comment 2 Keyue Hu 2016-12-15 14:36:34 UTC 
to be correct, the upstream might have the same issue.
Comment 3 Carlos O'Donell 2016-12-16 01:50:12 UTC 
There are no cancellation points in __socket or __bind.

Cancellation points in those functions would violate the POSIX requirements that no additional cancellation points be present other than those here:
 2.9.5 Thread Cancellation
http://pubs.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_09.html
"An implementation shall not introduce cancellation points into any other functions specified in this volume of IEEE Std 1003.1-2001."

However, in make_request, there is a __sendto, __recvmsg, and__netlink_assert_response, all of which could be cancellable and that would cause the lock to be lost and the subsequent __check_pf to hang.

There is a _lot_ of code running in make_request, the simplest solution is to push a cleanup handler to unlock the lock.

I've filed an upstream bug for this.
https://sourceware.org/bugzilla/show_bug.cgi?id=20975

Thanks for the bug report.
Comment 4 Keyue Hu 2016-12-16 02:36:23 UTC 
Yeah, only __sendto and __recvmsg are cancellable. 

and it is kind of you to fillup upstream bug. thanks!
Comment 6 Carlos O'Donell 2019-06-18 19:34:34 UTC 
Red Hat Enterprise Linux 7 is entering Maintenance Phase Support 1 this year and as such this issue will not be considered for fixing in RHEL 7 and is being closed. If you still encounter this issue with Red Hat Enterprise Linux 8, then please open a new issue with such details. Note that the upstream issue will remain for upstream tracking.
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