Bug 873286 - race condition : master pty used in mom_reader()/mom_writer() alternates blocking and non blocking state
Summary: race condition : master pty used in mom_reader()/mom_writer() alternates bloc...
Keywords:
Status: CLOSED WONTFIX
Alias: None
Product: Fedora
Classification: Fedora
Component: torque
Version: 16
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: ---
Assignee: Haïkel Guémar
QA Contact: Fedora Extras Quality Assurance
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2012-11-05 13:50 UTC by Fabrice Bellet
Modified: 2013-02-13 15:32 UTC (History)
2 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2013-02-13 15:32:22 UTC
Type: Bug
Embargoed:


Attachments (Terms of Use)

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.
Approximately 4 (four) weeks from now Fedora will stop maintaining
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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no longer maintained, which means that it will not receive any further 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.


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