Kernel [memory] tweaking question

[Robert Watson]

On Thu, 7 Apr 2005, Zera William Holladay wrote:

> On Thu, 7 Apr 2005, Peter Jeremy wrote:
>> These are all reasonably well documented in sys/conf/NOTES.  If you
>> want more detail, try a SystemV-oriented Unix book
>>
>> Close - they only control SystemV shared memory.  Sane shared memory
>> is available via mmap(2).  SystemV semaphores are controlled via
>> SEMxxx options.  Posix semaphores are listed as 'experimental'.
>
> Is there any chance that POSIX semaphores will be anything other than 
> experimental in the future, or is there no interest?  Further, the man 
> page indicates that the FreeBSD, POSIX semaphore implementation is not 
> capable of supporting multiple process semaphores.  I saw a similar note 
> on a Linux man page.  I think this is a shame, since POSIX semaphores 
> seem to be well designed (from a user point of view) compared to SYSV 
> semaphores, which are a total mess.

I haven't read the man page recently, but I've used our POSIX semaphores 
in an inter-process form successfully, and fixed a bug in them relating to 
fork relatively recently.  My understanding is that some issues may remain 
in the handling of error cases when semaphore support isn't present -- 
whether the process is terminated, or gets ENOSYS, depending on whether 
the program is linked against libpthread or not.  The fix for fork() 
handling will be present in 5.4-RELEASE.

Robert N M Watson