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Bug 607262 - Read from /proc/xen/xenbus does not honor O_NONBLOCK
Summary: Read from /proc/xen/xenbus does not honor O_NONBLOCK
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: kernel
Version: 6.0
Hardware: All
OS: Linux
low
low
Target Milestone: rc
: ---
Assignee: Paolo Bonzini
QA Contact: Boris Ranto
URL:
Whiteboard:
Depends On: 470801
Blocks: 523117
TreeView+ depends on / blocked
 
Reported: 2010-06-23 16:28 UTC by Paolo Bonzini
Modified: 2011-08-30 07:26 UTC (History)
6 users (show)

Fixed In Version: kernel-2.6.32-112.el6
Doc Type: Bug Fix
Doc Text:
Clone Of: 470801
Environment:
Last Closed: 2011-05-23 20:40:10 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2011:0542 0 normal SHIPPED_LIVE Important: Red Hat Enterprise Linux 6.1 kernel security, bug fix and enhancement update 2011-05-19 11:58:07 UTC

Description Paolo Bonzini 2010-06-23 16:28:27 UTC 
+++ This bug was initially created as a clone of Bug #470801 +++

Description of problem:
After open(2) on /proc/xen/xenbus with O_NONBLOCK flag, read(2) on the
file is blocked, and wait for an event.

Version-Release number of selected component (if applicable):
kernel-xen-2.6.18-92.el5

How reproducible:
Always

Steps to Reproduce:
1. open ("/proc/xen/xenbus", O_RDONLY | O_NONBLOCK);
2. read (fd, buf, 4096);
  
Actual results:
read(2) is blocked.

Expected results:
read(2) shall return EAGAIN.

--- Additional comment from bburns on 2009-02-24 14:47:39 EST ---

Assigned.

--- Additional comment from pm-rhel on 2010-02-09 17:38:06 EST ---

Since the release flag was set to ? after the pm_ack flag was set
to + (was likely set for the previous release), the pm_ack flag has
been reset to ? by the bugbot (pm-rhel). This action ensures the
proper review by Product Management.
Comment 2 RHEL Program Management 2010-06-23 16:52:55 UTC 
This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux major release.  Product Management has requested further
review of this request by Red Hat Engineering, for potential inclusion in a Red
Hat Enterprise Linux Major release.  This request is not yet committed for
inclusion.
Comment 3 Paolo Bonzini 2010-06-24 16:08:02 UTC 
reproducer:

#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
int main()
{
  char buf[256];
  int fd = open ("/proc/xen/xenbus", O_RDONLY | O_NONBLOCK); 
  if (fd == -1) {
    perror ("/proc/xen/xenbus");
    exit (1);
  }
  alarm (5);
  while (read (fd, buf, 256) == -1 && errno != EAGAIN)
    ;
  puts ("works");
  exit (0);
}
Comment 4 RHEL Program Management 2010-07-15 14:26:23 UTC 
This issue has been proposed when we are only considering blocker
issues in the current Red Hat Enterprise Linux release. It has
been denied for the current Red Hat Enterprise Linux release.

** If you would still like this issue considered for the current
release, ask your support representative to file as a blocker on
your behalf. Otherwise ask that it be considered for the next
Red Hat Enterprise Linux release. **
Comment 7 RHEL Program Management 2010-11-19 20:19:35 UTC 
This request was evaluated by Red Hat Product Management for inclusion
in a Red Hat Enterprise Linux maintenance release. Product Management has 
requested further review of this request by Red Hat Engineering, for potential
inclusion in a Red Hat Enterprise Linux Update release for currently deployed 
products. This request is not yet committed for inclusion in an Update release.
Comment 8 Paolo Bonzini 2011-01-05 10:43:20 UTC 
It's upstream commit 6280f190 (from 2.6.36).
Comment 9 Aristeu Rozanski 2011-02-03 15:39:20 UTC 
Patch(es) available on kernel-2.6.32-112.el6
Comment 13 errata-xmlrpc 2011-05-23 20:40:10 UTC 
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHSA-2011-0542.html
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