linux-kernel - Re: smpboot: CPU numbers printed as warning

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Message-ID: <YCu8KIM2kt6mb1Ol@hirez.programming.kicks-ass.net>
Date:   Tue, 16 Feb 2021 13:35:52 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Paul Menzel <pmenzel@...gen.mpg.de>
Cc:     Borislav Petkov <bp@...en8.de>, Petr Mladek <pmladek@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        LKML <linux-kernel@...r.kernel.org>, it+linux-x86@...gen.mpg.de,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        John Ogness <john.ogness@...utronix.de>
Subject: Re: smpboot: CPU numbers printed as warning

On Tue, Feb 16, 2021 at 12:58:19PM +0100, Paul Menzel wrote:
> Dear Borislav, dear Petr,
> 
> 
> Am 16.02.21 um 11:14 schrieb Borislav Petkov:
> > On Tue, Feb 16, 2021 at 10:49:04AM +0100, Petr Mladek wrote:
> > > Also you should add '\n' into the previous string to make the behavior
> > > clear. It will always be printed on a new line when pr_info()
> > > is used.
> > 
> > This was made to use pr_cont() on purpose so that the output is compact,
> > for example:
> > 
> > [    4.088605] x86: Booting SMP configuration:
> > [    4.089511] .... node  #0, CPUs:          #1   #2   #3   #4   #5   #6   #7   #8   #9  #10  #11  #12  #13  #14  #15  #16  #17  #18  #19  #20  #21  #22  #23  #24  #25  #26  #27  #28  #29  #30  #31  #32  #33  #34  #35  #36  #37  #38  #39  #40  #41  #42  #43  #44  #45  #46  #47  #48  #49  #50  #51  #52  #53  #54  #55  #56  #57  #58  #59  #60  #61  #62  #63
> > [    4.188510] .... node  #1, CPUs:    #64  #65  #66  #67  #68  #69  #70  #71  #72  #73  #74  #75  #76  #77  #78  #79  #80  #81  #82  #83  #84  #85  #86  #87  #88  #89  #90  #91  #92  #93  #94  #95  #96  #97  #98  #99 #100 #101 #102 #103 #104 #105 #106 #107 #108 #109 #110 #111 #112 #113 #114 #115 #116 #117 #118 #119 #120 #121 #122 #123 #124 #125 #126 #127
> > [    4.307511] .... node  #0, CPUs:   #128 #129 #130 #131 #132 #133 #134 #135 #136 #137 #138 #139 #140 #141 #142 #143 #144 #145 #146 #147 #148 #149 #150 #151 #152 #153 #154 #155 #156 #157 #158 #159 #160 #161 #162 #163 #164 #165 #166 #167 #168 #169 #170 #171 #172 #173 #174 #175 #176 #177 #178 #179 #180 #181 #182 #183 #184 #185 #186 #187 #188 #189 #190 #191
> > [    4.416511] .... node  #1, CPUs:   #192 #193 #194 #195 #196 #197 #198 #199 #200 #201 #202 #203 #204 #205 #206 #207 #208 #209 #210 #211 #212 #213 #214 #215 #216 #217 #218 #219 #220 #221 #222 #223 #224 #225 #226 #227 #228 #229 #230 #231 #232 #233 #234 #235 #236 #237 #238 #239 #240 #241 #242 #243 #244 #245 #246 #247 #248 #249 #250 #251 #252 #253 #254 #255
> > [    4.531683] smp: Brought up 2 nodes, 256 CPUs
> > [    4.534510] smpboot: Max logical packages: 2
> > [    4.535527] smpboot: Total of 256 processors activated (1147449.34 BogoMIPS)
> 
> Yes, the intention is clear, but it’s not working perfectly in all
> situations. Any ideas, how to improve that? After reading John’s response,
> I’d go with `pr_cont(KERN_INFO "message part");`.
> 
> By the way, what are these CPU numbers useful for? Isn’t
> 
>     smp: Brought up 2 nodes, 256 CPUs
> 
> enough information, and nothing else needed for the majority of users?

Majority yes, the primary use case is knowing which CPU is failing to
come up. Hardly ever happens, but when it does, its bloody annoying to
not know :-)

Also, the majority of people only has a hand full of CPUs, so they don't
care either way.