Are semaphores initialized?

Jim Barton jmb at patton.sgi.com
Fri May 26 08:16:07 AEST 1989


In article <9893 at watcgl.waterloo.edu>, fjhenigman at watcgl.waterloo.edu (Frank J. Henigman) writes:
> Can someone from SGI answer this?  I scoured the documentation with no luck.
> Are semaphores created with semget(2) initialized to some value (like zero)?
> -- 
> fjhenigman at watcgl.uwaterloo.ca                       Computer Graphics Lab
> fjhenigman at watcgl.waterloo.edu   Frank J. Henigman   University of Waterloo
>  ...!watmath!watcgl!fjhenigman                       Waterloo, Ontario, Canada

I perused sem.c (the semaphore code) and it appears that semaphores are not
initialized each time they are allocated.  The kernel uses a static area
for the semaphores (thus those wonderful SEM* constants in master.d/kernel)
and a chunk of them is allocated for each semget with no initialization.

One could argue (rightly) that this is a bug (especially for a secure system),
but this is what AT&T ships us.  I'll turn in a bug report locally, so we
remember to set them to something like zero.  If you wish to write portable
code, however, you should always assume that they are not initialized.

-- Jim Barton
Silicon Graphics Computer Systems    "UNIX: Live Free Or Die!"
jmb at sgi.sgi.com, sgi!jmb at decwrl.dec.com, ...{decwrl,sun}!sgi!jmb

  "I used to be disgusted, now I'm just amused."
			- Elvis Costello, 'Red Shoes'
--



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