On 3/26/20 8:38 PM, Xi Ruoyao via blfs-dev wrote:
On 2020-03-26 23:22 +0000, Ken Moffat via blfs-dev wrote:
On Thu, Mar 26, 2020 at 10:57:03PM +0100, Pierre Labastie via blfs-dev wrote:
(asking about only one item)
If you do not do this, configuring will fail with a python traceback
report referencing a /usr/lib/pythonN.N/multiprocessing/synchronize.py
file and ending 'OSError: [Errno 38] Function not implemented'.
(this explanation possibly in italics, i.e. emphasis, except for the
filename markup)
As the starter of this thread, I do not see exactly this error, but rather:
File "/usr/lib/python2.7/multiprocessing/synchronize.py", line 59, in
<module>
" function, see issue 3770.")
ImportError: This platform lacks a functioning sem_open implementation,
therefore, the required synchronization primitives needed will not function,
see issue 3770.
from tmpfs (5):
A tmpfs filesystem mounted at /dev/shm is used for the implementation
of POSIX shared memory (shm_overview(7)) and POSIX semaphores
(sem_overview(7)).
In kernel doc (Documentation/filesystems/tmpfs.txt):
2) glibc 2.2 and above expects tmpfs to be mounted at /dev/shm for
POSIX shared memory (shm_open, shm_unlink). Adding the following
line to /etc/fstab should take care of this:
tmpfs /dev/shm tmpfs defaults 0 0
Remember to create the directory that you intend to mount tmpfs on
if necessary.
This mount is _not_ needed for SYSV shared memory. The internal
mount is used for that. (In the 2.3 kernel versions it was
necessary to mount the predecessor of tmpfs (shm fs) to use SYSV
shared memory)
So I think we should mount a tmpfs to /dev/shm, anyway.
In lfs-systemd it's automatically done by systemd. In lfs-sysv book the
mountvirtfs bootscript makes /run/shm and link it to /dev/shm. I think it's a
"hack" which is deprecated, and shall be replaced with a line mounting a tmpfs
to /dev/shm, in /etc/fstab.
If /dev/shm is a symlink to /run/shm and /run is a tmpfs and shm is a
subdirectory of /run, what is the difference? There is one level of
indirection with the symlink, but any operations end up on a tmpfs now.
-- Bruce
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