Bug 873286

Summary:	race condition : master pty used in mom_reader()/mom_writer() alternates blocking and non blocking state
Product:	[Fedora] Fedora	Reporter:	Fabrice Bellet <fabrice>
Component:	torque	Assignee:	Haïkel Guémar <karlthered>
Status:	CLOSED WONTFIX	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	16	CC:	fotis, karlthered
Target Milestone:	---
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2013-02-13 15:32:22 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Fabrice Bellet 2012-11-05 13:50:58 UTC

Hi!

I noticed that the file descriptor of the master pty shared by parent and child pbs_mom processes alternates between blocking and non blocking state. 

The consequence of this race condition is that read() from mom_writer() sometimes fails, and returns -1, with errno=EAGAIN (which is the expected behaviour when the related file descriptor is not blocking, but this is not expected by the code of mom_writer()), causing the submitted task to terminate unexpectedly.

The problem is caused because the corresponding mom_reader() function, from the other process calls write() on this same pty, this function is #defined to write_nonblocking_socket(), and this function temporally change the state of the pty from blocking to non_blocking.

I experience this problem systematically in a VM running Fedora 16 x86_64, when submitting interactive jobs. REproducing this case on real hardware (same distro, same packages) is much more difficult.

A possible fix would be to  gracefully handle the EAGAIN errno in the mom_writer() loop.

Comment 1 Fedora End Of Life 2013-01-16 14:28:45 UTC

This message is a reminder that Fedora 16 is nearing its end of life.
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Comment 2 Fedora End Of Life 2013-02-13 15:32:25 UTC

Fedora 16 changed to end-of-life (EOL) status on 2013-02-12. Fedora 16 is 
no longer maintained, which means that it will not receive any further 
security or bug fix updates. As a result we are closing this bug.

If you can reproduce this bug against a currently maintained version of 
Fedora please feel free to reopen this bug against that version.

Thank you for reporting this bug and we are sorry it could not be fixed.