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Semaphores Continue Biting Intel Linux Users

Intel

Published on 23 December 2011 04:50 PM EST
Written by Michael Larabel in Intel
3 Comments

It turns out the semaphore issues for Intel Sandy Bridge Linux users continues to be present and it's resulting in the patch from the recent Intel merge having to be changed at the last minute within the Linux 3.2 kernel.

With the Linux 3.2-rc6 kernel, the use of semaphores were flipped on when the Intel I/O re-mapping is turned off. But it turns out that semaphores on Sandy Bridge hardware is still problematic.

For those that don't recall, semaphore issues borked the Linux 2.6.39 kernel at the last minute for Sandy Bridge owners too. Semaphores also caused problems during the Linux 2.6.38 kernel. With the Linux 3.2 kernel, it was attempted to flip it back on again for Sandy Bridge and Ivy Bridge hardware, but there's at least one report of hardware hanging when this feature is enabled.

This option though can at least be easily toggled using the i915.semaphores=1 kernel module parameter. (The 2.6.39 Phoronix article explains the issue in greater detail.)

Due to this problem, Keith Packard just sent in a Friday afternoon patch to turn off semaphores by default for Sandy. Semaphores for Ivy Bridge is still left on, which hopefully means the support is more reliable there or at least with their current pre-production development systems as the IVB hardware is still a few months from shipping to the public.

The patch changing the default can be found on the Linux kernel mailing list.

About The Author
Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via and or contacted via .
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