In /usr/share/cmake/Modules/ProcessorCount.cmake cmake checks for the number of processors using sysctl -n hw.ncpu This is done in the line: execute_process(COMMAND ${ProcessorCount_cmd_sysctl} -n hw.ncpu In kernel 4.9.9 the /proc/sys/hw/ncpu is missing and sysctl just stays there forever. As a work around, I changed the line to read execute_process(COMMAND echo 48 as I have 48 cpus and I can continue doing work.
Can you tell which package failed for you because of this? Also, I just added cmake-3.8.0_rc1 to the tree but without any KEYWORDS. Can you perhaps test if this is still an issue with cmake-3.8?
Are you certain that it's sysctl -n hw.ncpu that's hanging? With kernel-4.7.10, cmake-3.7.2 and procps-3.3.12 I have the sysctl failure: # sysctl -n hw.ncpu sysctl: cannot stat /proc/sys/hw/ncpu: No such file or directory but cmake is successfully able to still continue (I guess with getconf _NPROCESSORS_ONLN).
Created attachment 463386 [details] CMakeLists.txt Test case to see how far cmake is getting.
Created attachment 463388 [details] ProcessorCountTest.cmake Module for testcase.
No, I don't know which package is affected. No, I don't know if it is the kernel version. But, before going home Thursday, I setup a build of the kernel to 4.9.9 and did the upgrade then poweroff. In the morning of Friday, I came to work, tried to open a project that I had been working on the previous day and Qt Creator would just sit there with the spinning circle. So I ran cmake manually and it would just stall completely. I ran strace and then found a coredump on the sysctl and discovered that the proc/sys/vm/ncpus was missing. I then fired up a fedora 25 VM with kernel 4.8 (I think) and found that this did exist there). I removed the line and was able to do work. I then decided to add the bug in case someone else had the same problem. I now realize that this was a mistake, and I apologize. I cannot tell you how sorry that I am, as I totally forgot that gentoo is all about the build system and nothing about the operating system.
There's no problem with this bug at all, I was just trying to narrow down further exactly what component could be causing it. Since your investigation seems to point to sysctl hanging (which as far as I know it should not), I suspect this is a problem in sys-process/procps. Are you able to add your emerge --info and procps version? Then we can ping the base-system team if they have some idea why this might happen.
