Bug 39094 - WaitFor does not handle EIO (causes 100% cpu load)
Summary: WaitFor does not handle EIO (causes 100% cpu load)
Alias: None
Product: xorg
Classification: Unclassified
Component: Server/General (show other bugs)
Version: git
Hardware: Other All
: high major
Assignee: Adam Jackson
QA Contact: Xorg Project Team
Whiteboard: 2012BRB_Reviewed
Depends on:
Blocks: xserver-1.12 xserver-1.13
  Show dependency treegraph
Reported: 2011-07-09 07:26 UTC by Chris Wilson
Modified: 2018-12-13 18:34 UTC (History)
2 users (show)

See Also:
i915 platform:
i915 features:


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Description Chris Wilson 2011-07-09 07:26:40 UTC
The device goes into a permanent input-ready state causing X's WaitForSomething to never actually wait.

open("/dev/vga_arbiter", O_RDWR)        = 10
read(10, "count:1,PCI:0000:00:02.0,decodes"..., 64) = 64
write(10, "target PCI:0000:00:02.0", 23) = 23
read(10, "count:1,PCI:0000:00:02.0,decodes"..., 64) = 64
select(256, [1 5 9 10 12 13 14 15 16 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52], NULL, NULL, {89, 869000}) = 1 (in [10], left {89, 868993})
clock_gettime(CLOCK_MONOTONIC, {17445, 90572053}) = 0
ioctl(10, TCFLSH, 0x2)                  = -1 EIO (Input/output error)
<repeat ad infinitum>

Even more annoying this is on a laptop with only a single igfx and no expansion capabilities...

Hopefully this in fact an old bug and already fixed.
Comment 1 Jeremy Huddleston Sequoia 2011-10-12 02:17:51 UTC
This is a tad out of my area of expertise, but it smells like this might be kernel related.  When did you start seeing this issue?  What kernel version doi you have?

Doing a google search for TCFLSH EIO returns some possibly similar results:

but those all look like an EIO of a TCFLSH of /dev/tty*

1) we should "deal" with the EIO elegantly in src/os/WaitFor.c

2) What can cause us to EIO /dev/vga_arbiter?  Will that occur if some other process open(2)s it?

Also, I'm a bit confused why we're select(2)ing the /dev/vga_arbiter descriptor in X's WaitForSomething.  I don't see how that descriptor is exposed by libpciacces.  I don't see "vgaarb_fd" in the server source, and I don't see a way in libpciaccess to add that descriptor to an fd_set.

AFAICT, that descriptor is *owned* by libpciaccess, so the server should not have it in its read fd_set.  Am I missing something here?
Comment 2 Jeremy Huddleston Sequoia 2011-10-12 02:19:45 UTC
Let's take care of #1 (handle EIO properly) in xserver-1.12, but I'm still perplexed about why that descriptor is in our fd_set ...
Comment 3 GitLab Migration User 2018-12-13 18:34:52 UTC
-- GitLab Migration Automatic Message --

This bug has been migrated to freedesktop.org's GitLab instance and has been closed from further activity.

You can subscribe and participate further through the new bug through this link to our GitLab instance: https://gitlab.freedesktop.org/xorg/xserver/issues/248.

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