view Documentation/ManagementStyle @ 452:c7ed6fe5dca0

kexec: dont initialise regions in reserve_memory()

There is no need to initialise efi_memmap_res and boot_param_res in
reserve_memory() for the initial xen domain as it is done in
machine_kexec_setup_resources() using values from the kexec hypercall.

Signed-off-by: Simon Horman <horms@verge.net.au>
author Keir Fraser <keir.fraser@citrix.com>
date Thu Feb 28 10:55:18 2008 +0000 (2008-02-28)
parents 831230e53067
line source
2 Linux kernel management style
4 This is a short document describing the preferred (or made up, depending
5 on who you ask) management style for the linux kernel. It's meant to
6 mirror the CodingStyle document to some degree, and mainly written to
7 avoid answering (*) the same (or similar) questions over and over again.
9 Management style is very personal and much harder to quantify than
10 simple coding style rules, so this document may or may not have anything
11 to do with reality. It started as a lark, but that doesn't mean that it
12 might not actually be true. You'll have to decide for yourself.
14 Btw, when talking about "kernel manager", it's all about the technical
15 lead persons, not the people who do traditional management inside
16 companies. If you sign purchase orders or you have any clue about the
17 budget of your group, you're almost certainly not a kernel manager.
18 These suggestions may or may not apply to you.
20 First off, I'd suggest buying "Seven Habits of Highly Successful
21 People", and NOT read it. Burn it, it's a great symbolic gesture.
23 (*) This document does so not so much by answering the question, but by
24 making it painfully obvious to the questioner that we don't have a clue
25 to what the answer is.
27 Anyway, here goes:
30 Chapter 1: Decisions
32 Everybody thinks managers make decisions, and that decision-making is
33 important. The bigger and more painful the decision, the bigger the
34 manager must be to make it. That's very deep and obvious, but it's not
35 actually true.
37 The name of the game is to _avoid_ having to make a decision. In
38 particular, if somebody tells you "choose (a) or (b), we really need you
39 to decide on this", you're in trouble as a manager. The people you
40 manage had better know the details better than you, so if they come to
41 you for a technical decision, you're screwed. You're clearly not
42 competent to make that decision for them.
44 (Corollary:if the people you manage don't know the details better than
45 you, you're also screwed, although for a totally different reason.
46 Namely that you are in the wrong job, and that _they_ should be managing
47 your brilliance instead).
49 So the name of the game is to _avoid_ decisions, at least the big and
50 painful ones. Making small and non-consequential decisions is fine, and
51 makes you look like you know what you're doing, so what a kernel manager
52 needs to do is to turn the big and painful ones into small things where
53 nobody really cares.
55 It helps to realize that the key difference between a big decision and a
56 small one is whether you can fix your decision afterwards. Any decision
57 can be made small by just always making sure that if you were wrong (and
58 you _will_ be wrong), you can always undo the damage later by
59 backtracking. Suddenly, you get to be doubly managerial for making
60 _two_ inconsequential decisions - the wrong one _and_ the right one.
62 And people will even see that as true leadership (*cough* bullshit
63 *cough*).
65 Thus the key to avoiding big decisions becomes to just avoiding to do
66 things that can't be undone. Don't get ushered into a corner from which
67 you cannot escape. A cornered rat may be dangerous - a cornered manager
68 is just pitiful.
70 It turns out that since nobody would be stupid enough to ever really let
71 a kernel manager have huge fiscal responsibility _anyway_, it's usually
72 fairly easy to backtrack. Since you're not going to be able to waste
73 huge amounts of money that you might not be able to repay, the only
74 thing you can backtrack on is a technical decision, and there
75 back-tracking is very easy: just tell everybody that you were an
76 incompetent nincompoop, say you're sorry, and undo all the worthless
77 work you had people work on for the last year. Suddenly the decision
78 you made a year ago wasn't a big decision after all, since it could be
79 easily undone.
81 It turns out that some people have trouble with this approach, for two
82 reasons:
83 - admitting you were an idiot is harder than it looks. We all like to
84 maintain appearances, and coming out in public to say that you were
85 wrong is sometimes very hard indeed.
86 - having somebody tell you that what you worked on for the last year
87 wasn't worthwhile after all can be hard on the poor lowly engineers
88 too, and while the actual _work_ was easy enough to undo by just
89 deleting it, you may have irrevocably lost the trust of that
90 engineer. And remember: "irrevocable" was what we tried to avoid in
91 the first place, and your decision ended up being a big one after
92 all.
94 Happily, both of these reasons can be mitigated effectively by just
95 admitting up-front that you don't have a friggin' clue, and telling
96 people ahead of the fact that your decision is purely preliminary, and
97 might be the wrong thing. You should always reserve the right to change
98 your mind, and make people very _aware_ of that. And it's much easier
99 to admit that you are stupid when you haven't _yet_ done the really
100 stupid thing.
102 Then, when it really does turn out to be stupid, people just roll their
103 eyes and say "Oops, he did it again".
105 This preemptive admission of incompetence might also make the people who
106 actually do the work also think twice about whether it's worth doing or
107 not. After all, if _they_ aren't certain whether it's a good idea, you
108 sure as hell shouldn't encourage them by promising them that what they
109 work on will be included. Make them at least think twice before they
110 embark on a big endeavor.
112 Remember: they'd better know more about the details than you do, and
113 they usually already think they have the answer to everything. The best
114 thing you can do as a manager is not to instill confidence, but rather a
115 healthy dose of critical thinking on what they do.
117 Btw, another way to avoid a decision is to plaintively just whine "can't
118 we just do both?" and look pitiful. Trust me, it works. If it's not
119 clear which approach is better, they'll eventually figure it out. The
120 answer may end up being that both teams get so frustrated by the
121 situation that they just give up.
123 That may sound like a failure, but it's usually a sign that there was
124 something wrong with both projects, and the reason the people involved
125 couldn't decide was that they were both wrong. You end up coming up
126 smelling like roses, and you avoided yet another decision that you could
127 have screwed up on.
130 Chapter 2: People
132 Most people are idiots, and being a manager means you'll have to deal
133 with it, and perhaps more importantly, that _they_ have to deal with
134 _you_.
136 It turns out that while it's easy to undo technical mistakes, it's not
137 as easy to undo personality disorders. You just have to live with
138 theirs - and yours.
140 However, in order to prepare yourself as a kernel manager, it's best to
141 remember not to burn any bridges, bomb any innocent villagers, or
142 alienate too many kernel developers. It turns out that alienating people
143 is fairly easy, and un-alienating them is hard. Thus "alienating"
144 immediately falls under the heading of "not reversible", and becomes a
145 no-no according to Chapter 1.
147 There's just a few simple rules here:
148 (1) don't call people d*ckheads (at least not in public)
149 (2) learn how to apologize when you forgot rule (1)
151 The problem with #1 is that it's very easy to do, since you can say
152 "you're a d*ckhead" in millions of different ways (*), sometimes without
153 even realizing it, and almost always with a white-hot conviction that
154 you are right.
156 And the more convinced you are that you are right (and let's face it,
157 you can call just about _anybody_ a d*ckhead, and you often _will_ be
158 right), the harder it ends up being to apologize afterwards.
160 To solve this problem, you really only have two options:
161 - get really good at apologies
162 - spread the "love" out so evenly that nobody really ends up feeling
163 like they get unfairly targeted. Make it inventive enough, and they
164 might even be amused.
166 The option of being unfailingly polite really doesn't exist. Nobody will
167 trust somebody who is so clearly hiding his true character.
169 (*) Paul Simon sang "Fifty Ways to Lose Your Lover", because quite
170 frankly, "A Million Ways to Tell a Developer He Is a D*ckhead" doesn't
171 scan nearly as well. But I'm sure he thought about it.
174 Chapter 3: People II - the Good Kind
176 While it turns out that most people are idiots, the corollary to that is
177 sadly that you are one too, and that while we can all bask in the secure
178 knowledge that we're better than the average person (let's face it,
179 nobody ever believes that they're average or below-average), we should
180 also admit that we're not the sharpest knife around, and there will be
181 other people that are less of an idiot that you are.
183 Some people react badly to smart people. Others take advantage of them.
185 Make sure that you, as a kernel maintainer, are in the second group.
186 Suck up to them, because they are the people who will make your job
187 easier. In particular, they'll be able to make your decisions for you,
188 which is what the game is all about.
190 So when you find somebody smarter than you are, just coast along. Your
191 management responsibilities largely become ones of saying "Sounds like a
192 good idea - go wild", or "That sounds good, but what about xxx?". The
193 second version in particular is a great way to either learn something
194 new about "xxx" or seem _extra_ managerial by pointing out something the
195 smarter person hadn't thought about. In either case, you win.
197 One thing to look out for is to realize that greatness in one area does
198 not necessarily translate to other areas. So you might prod people in
199 specific directions, but let's face it, they might be good at what they
200 do, and suck at everything else. The good news is that people tend to
201 naturally gravitate back to what they are good at, so it's not like you
202 are doing something irreversible when you _do_ prod them in some
203 direction, just don't push too hard.
206 Chapter 4: Placing blame
208 Things will go wrong, and people want somebody to blame. Tag, you're it.
210 It's not actually that hard to accept the blame, especially if people
211 kind of realize that it wasn't _all_ your fault. Which brings us to the
212 best way of taking the blame: do it for another guy. You'll feel good
213 for taking the fall, he'll feel good about not getting blamed, and the
214 guy who lost his whole 36GB porn-collection because of your incompetence
215 will grudgingly admit that you at least didn't try to weasel out of it.
217 Then make the developer who really screwed up (if you can find him) know
218 _in_private_ that he screwed up. Not just so he can avoid it in the
219 future, but so that he knows he owes you one. And, perhaps even more
220 importantly, he's also likely the person who can fix it. Because, let's
221 face it, it sure ain't you.
223 Taking the blame is also why you get to be manager in the first place.
224 It's part of what makes people trust you, and allow you the potential
225 glory, because you're the one who gets to say "I screwed up". And if
226 you've followed the previous rules, you'll be pretty good at saying that
227 by now.
230 Chapter 5: Things to avoid
232 There's one thing people hate even more than being called "d*ckhead",
233 and that is being called a "d*ckhead" in a sanctimonious voice. The
234 first you can apologize for, the second one you won't really get the
235 chance. They likely will no longer be listening even if you otherwise
236 do a good job.
238 We all think we're better than anybody else, which means that when
239 somebody else puts on airs, it _really_ rubs us the wrong way. You may
240 be morally and intellectually superior to everybody around you, but
241 don't try to make it too obvious unless you really _intend_ to irritate
242 somebody (*).
244 Similarly, don't be too polite or subtle about things. Politeness easily
245 ends up going overboard and hiding the problem, and as they say, "On the
246 internet, nobody can hear you being subtle". Use a big blunt object to
247 hammer the point in, because you can't really depend on people getting
248 your point otherwise.
250 Some humor can help pad both the bluntness and the moralizing. Going
251 overboard to the point of being ridiculous can drive a point home
252 without making it painful to the recipient, who just thinks you're being
253 silly. It can thus help get through the personal mental block we all
254 have about criticism.
256 (*) Hint: internet newsgroups that are not directly related to your work
257 are great ways to take out your frustrations at other people. Write
258 insulting posts with a sneer just to get into a good flame every once in
259 a while, and you'll feel cleansed. Just don't crap too close to home.
262 Chapter 6: Why me?
264 Since your main responsibility seems to be to take the blame for other
265 peoples mistakes, and make it painfully obvious to everybody else that
266 you're incompetent, the obvious question becomes one of why do it in the
267 first place?
269 First off, while you may or may not get screaming teenage girls (or
270 boys, let's not be judgmental or sexist here) knocking on your dressing
271 room door, you _will_ get an immense feeling of personal accomplishment
272 for being "in charge". Never mind the fact that you're really leading
273 by trying to keep up with everybody else and running after them as fast
274 as you can. Everybody will still think you're the person in charge.
276 It's a great job if you can hack it.