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Bug 1597384

Summary:	Async operations can hang when the server is running nunc-stans
Product:	Red Hat Enterprise Linux 7	Reporter:	mreynolds
Component:	389-ds-base	Assignee:	thierry bordaz <tbordaz>
Status:	CLOSED ERRATA	QA Contact:	RHDS QE <ds-qe-bugs>
Severity:	urgent	Docs Contact:
Priority:	urgent
Version:	7.4	CC:	cobrown, dberry, dminnich, ekeck, gparente, jvilicic, mreynolds, msecaur, nkinder, rmeggins
Target Milestone:	rc	Keywords:	ZStream
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:	389-ds-base-1.3.8.4-1.el7	Doc Type:	No Doc Update
Doc Text:	undefined	Story Points:	---
Clone Of:
Clones:	1597530 (view as bug list)		Environment:
Last Closed:	2018-10-30 10:14:34 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	1597530

Description mreynolds 2018-07-02 20:02:14 UTC

This bug is created as a clone of upstream ticket:
https://pagure.io/389-ds-base/issue/49765

#### Issue Description
This bug is a side effect of https://pagure.io/389-ds-base/issue/48184

With async operations on the same connection, the connection can be set several times in read_ready. This is done with connection_threadmain scheduling ns_handle_pr_read_ready (connection_make_readable_nolock).

When there is no more activity on the connection (no new req, timeout, closure..) and the server is listening to it (ns_handle_pr_read_ready), then if an async operation tries to schedule ns_handle_pr_read_ready it will hang (before completing the operation).

The consequence is one or more hanging operations on the connection with a stack like

    Thread 63 (Thread 0x7f794a711700 (LWP 28798)):
    #0  0x00007f7995e75c93 in select () from /lib64/libc.so.6
    #1  0x00007f7998e8046b in DS_Sleep (ticks=100) at 389-ds-base/ldap/servers/slapd/util.c:1086
    #2  0x0000000000438a6a in ns_connection_post_io_or_closing (conn=0x7f79550fc800) at 389-ds-base/ldap/servers/slapd/daemon.c:1835
    #3  0x0000000000427adc in connection_make_readable_nolock (conn=0x7f79550fc800) at 389-ds-base/ldap/servers/slapd/connection.c:1361                                                                                              
    #4  0x0000000000429e91 in connection_threadmain () at 389-ds-base/ldap/servers/slapd/connection.c:1724
    #5  0x00007f7996a0907b in _pt_root () from /lib64/libnspr4.so
    #6  0x00007f79965ab36d in start_thread () from /lib64/libpthread.so.0
    #7  0x00007f7995e7fb4f in clone () from /lib64/libc.so.6      

A way to mitigate the problem is to set a idletimeout

#### Package Version and Platform
1.3.7, 1.3.8 and master


#### Steps to reproduce

test case is not systematic.
On rapid machine, it hangs one out of ten

#### Actual results
Some operations are not completing (hanging)

#### Expected results
Should not hang

Comment 6 German Parente 2018-08-01 16:08:11 UTC

*** Bug 1600764 has been marked as a duplicate of this bug. ***

Comment 7 Viktor Ashirov 2018-08-30 13:22:56 UTC

Build tested: 389-ds-base-1.3.8.4-12.el7.x86_64

Cmocka unit tests pass:

PASS: test_nuncstans
PASS: test_nuncstans_stress_small
PASS: test_nuncstans_stress_large

No hang was observed during the acceptance testing with nunc-stans. NS is also disabled by default on new installs (bz1614501), so marking as VERIFIED, SanityOnly.

Comment 14 errata-xmlrpc 2018-10-30 10:14:34 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2018:3127