Bug 9058

Summary:	cpu hotplug support broken in 2.6.23-rc3
Product:	Other	Reporter:	Rafael J. Wysocki (rjwysocki)
Component:	Other	Assignee:	Rafael J. Wysocki (rjwysocki)
Status:	RESOLVED CODE_FIX
Severity:	normal	CC:	pavel, tglx
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	2.6.23-rc3	Subsystem:
Regression:	Yes	Bisected commit-id:
Bug Depends on:
Bug Blocks:	9056

Description Rafael J. Wysocki 2007-09-23 14:37:40 UTC

References      : http://lkml.org/lkml/2007/8/27/58
                  http://lkml.org/lkml/2007/9/3/65
Submitter       : Pavel Machek <pavel@ucw.cz>
Handled-By      : Thomas Gleixner <tglx@linutronix.de>

Comment 1 Rafael J. Wysocki 2007-09-23 14:45:10 UTC

Fixed by commit 5e41d0d60a534d2a5dc9772600a58f44c8d12506

Comment 2 Rafael J. Wysocki 2007-09-24 08:46:19 UTC

(In reply to comment #1)
> Fixed by commit 5e41d0d60a534d2a5dc9772600a58f44c8d12506

Commit:	5e41d0d60a534d2a5dc9772600a58f44c8d12506
Parent:	31d9b3938c0459e5e9755ce0a98ac1e24eeff972
Author:	Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Sun, 16 Sep 2007 13:36:43 +0000 (15:36 +0200)
Committer: Thomas Gleixner <tglx@chaos.(none)>
CommitDate: Sun, 16 Sep 2007 13:36:43 +0000 (15:36 +0200)

clockevents: prevent stale tick update on offline cpu

"http://git.kernel.org/gitweb.cgi?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=5e41d0d60a534d2a5dc9772600a58f44c8d12506"

Comment 3 Rafael J. Wysocki 2007-10-02 12:49:46 UTC

Reopened because of: http://lkml.org/lkml/2007/10/2/104

Comment 4 Thomas Gleixner 2007-10-02 16:02:47 UTC

Hmm,

root@amd:/sys/devices/system/cpu/cpu1# echo 0 > online
root@amd:/sys/devices/system/cpu/cpu1# echo 0 > online
-bash: echo: write error: Device or resource busy

The second one fails. The cpu _IS_ already offline. otherwise the first one would not have come back. Thats the problem which was caused by the subtle clock events thinkos. The clock event bugs made the first one to be stuck for ever.
That's a different problem. Did this ever work ?

root@amd:/sys/devices/system/cpu/cpu1# echo 1 > online
-bash: echo: write error: Device or resource busy

This might be a follow up error caused by the second write.

I do not see how this should be connected to the clock events problems which we had before.

Pavel, does the following work ?

root@amd:/sys/devices/system/cpu/cpu1# echo 0 > online
root@amd:/sys/devices/system/cpu/cpu1# echo 1 > online

Is your double offline problem really a new one in .23 ?

Comment 5 Rafael J. Wysocki 2007-10-06 07:20:23 UTC

Pavel?

Comment 6 Pavel Machek 2007-11-15 14:23:59 UTC

(Sorry for delay)

Yes, repeated offlines/onlines seem to work now. echo 0, twice, is probably different issue. So I guess this is "CODE_FIX" now.