5

Doing man statfs on my system tell me that __SWORD_TYPE f_type can be a list of arbitrary values which are defined in header files.

Why is FUTEXFS_SUPER_MAGIC defined as 0xBAD1DEA, which obviously mean "bad idea" in plain English? Is this number just a joke or is this filesystem particularly bad, dangerous...?

3

Yes, it's a bad idea — and it was removed in 2008, after being deprecated in October 2006 by Andrew Morton:

Apparently FUTEX_FD is unfixably racy and nothing uses it (or if it does, it shouldn't).

(Thanks to AlexP for finding the deprecation message.)

  • 1
    Andrew Morton, announcing the scheduled removal of FUTEX_FD (November 2006), yqcomputer.com/1272_16484_1.htm: "apparently FUTEX_FD is unfixably racy and nothing uses it (or if it does, it shouldn't)". – AlexP Nov 18 '16 at 15:44
  • 1
    See also the changelog for 2.5.26 where Al Viro complains about the state of futex.c. – Stephen Kitt Nov 18 '16 at 15:54
  • Was there a world before 2.6? – AlexP Nov 18 '16 at 16:00

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