Bug 673983
| Summary: | virtio_console driver never returns from selecting for write when the queue is full [rhel-5.6.z] | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 5 | Reporter: | RHEL Program Management <pm-rhel> |
| Component: | kernel | Assignee: | Jiri Pirko <jpirko> |
| Status: | CLOSED ERRATA | QA Contact: | Red Hat Kernel QE team <kernel-qe> |
| Severity: | medium | Docs Contact: | |
| Priority: | high | ||
| Version: | 5.7 | CC: | amit.shah, bcao, dhoward, hdegoede, mjenner, pm-eus, rkhan, virt-maint |
| Target Milestone: | rc | Keywords: | ZStream |
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | kernel-2.6.18-238.4.1.el5 | Doc Type: | Bug Fix |
| Doc Text: |
Using a virtio serial port from an application, filling it until the write command returns -EAGAIN and then executing a select command for the write command caused the select command to not return any values, when using the virtio serial port in a non-blocking mode. When used in a blocking mode, the write command waited until the host indicated it used up the buffers. This was due to the fact that the poll operation waited for the port->waitqueue pointer, however, nothing woke the waitqueue when there was room again in the queue. With this update, the queue is woken via host notifications so that buffers consumed by the host can be reclaimed, the queue freed, and the application write operations may proceed again.
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Story Points: | --- |
| Clone Of: | Environment: | ||
| Last Closed: | 2011-03-01 20:31:03 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: | 673459 | ||
| Bug Blocks: | |||
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Description
RHEL Program Management
2011-01-31 09:14:41 UTC
in kernel-2.6.18-238.4.1.el5 linux-2.6-char-virtio-wake-console-outvq-on-host-notifications.patch Verified on qemu-kvm-0.12.1.2-2.144.el6.
guest kernel : kernel-2.6.18-238.4.1.el5
steps:
1.start VM with virtio-serial-port w/o -M parameter.
2.open the socket file on the host and not read it
eg:#cat open-socket
#!/usr/bin/python
import os
import sys
import socket
import time
#fd = os.open(sys.argv[1], os.O_RDONLY)
s = socket.socket(socket.AF_UNIX)
s.connect(sys.argv[1])
while 1:
# do nothing
time.sleep(1)
#python open-socket /tmp/vport0
3.transfer a file whose size > 2G via virtio-serial
eg :#cat /tt > /dev/vport0p1
Actual Results:
qemu-kvm process does not freeze.
Based on above ,this issue has been fixed.
Change status to VERIFIED.
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-2011-0303.html
Technical note added. If any revisions are required, please edit the "Technical Notes" field
accordingly. All revisions will be proofread by the Engineering Content Services team.
New Contents:
Using a virtio serial port from an application, filling it until the write command returns -EAGAIN and then executing a select command for the write command caused the select command to not return any values, when using the virtio serial port in a non-blocking mode. When used in a blocking mode, the write command waited until the host indicated it used up the buffers. This was due to the fact that the poll operation waited for the port->waitqueue pointer, however, nothing woke the waitqueue when there was room again in the queue. With this update, the queue is woken via host notifications so that buffers consumed by the host can be reclaimed, the queue freed, and the application write operations may proceed again.
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