1 .. SPDX-License-Identifier: GPL-2.0
2
3 ==========================
4 File Locking Release Notes
5 ==========================
6
7 Andy Walker <andy@lysaker.kvaer
8
9 12 May 1997
10
11
12 1. What's New?
13 ==============
14
15 1.1 Broken Flock Emulation
16 --------------------------
17
18 The old flock(2) emulation in the kernel was s
19 compatible flock(2) support in the 1.3.x serie
20 release of the 2.1.x kernel series, support fo
21 been totally removed, so that we don't need to
22 forever.
23
24 This should not cause problems for anybody, si
25 2.1.x kernel should have updated their C libra
26 anyway (see the file "Documentation/process/ch
27
28 1.2 Allow Mixed Locks Again
29 ---------------------------
30
31 1.2.1 Typical Problems - Sendmail
32 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
33 Because sendmail was unable to use the old flo
34 installations use fcntl() instead of flock().
35 for example. This gave rise to some other subt
36 configured to rebuild the alias file. Sendmail
37 file with fcntl() at the same time as the GDBM
38 file with flock(). With pre 1.3.96 kernels thi
39 over time, or under a very heavy mail load, wo
40 to lock solid with deadlocked processes.
41
42
43 1.2.2 The Solution
44 ^^^^^^^^^^^^^^^^^^
45 The solution I have chosen, after much experim
46 is to make flock() and fcntl() locks oblivious
47 exists, and neither will have any effect on th
48
49 I wanted the two lock styles to be cooperative
50 race and deadlock conditions that the current
51 practical one. It puts us in the same position
52 4.1.x and several other commercial Unices. The
53 cooperative flock()/fcntl() are those that emu
54 fcntl(), with all the problems that implies.
55
56
57 1.3 Mandatory Locking As A Mount Option
58 ---------------------------------------
59
60 Mandatory locking was prior to this release a
61 that was valid for all mounted filesystems. T
62 dangers, not the least of which was the abilit
63 asking it to read a file for which a mandatory
64
65 Such option was dropped in Kernel v5.14.
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