linux-kernel - [Patch] restore the RCU callback to defer put_task

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 7 Aug 2006 19:56:15 -0700
From:	Bill Huey (hui) <billh@...ppy.monkey.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Robert Crocombe <rcrocomb@...il.com>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Darren Hart <dvhltc@...ibm.com>
Subject: [Patch] restore the RCU callback to defer put_task_struct() Re: Problems with 2.6.17-rt8

On Thu, Aug 03, 2006 at 10:27:41AM -0400, Steven Rostedt wrote:

...(output and commentary a log deleted)...

> This could also have a side effect that messes things up.
> 
> Unfortunately, right now I'm assigned to other tasks and I cant spend
> much more time on this at the moment.  So hopefully, Ingo, Thomas or
> Bill, or someone else can help you find the reason for this problem.

Steve and company,

Speaking of which, after talking to Steve about this and confirming this
with a revert of changes. put_task_struct() can't deallocated memory from
either the zone or SLAB cache without taking a sleeping lock. It can't
be called directly from finish_task_switch to reap the thread because of
that (violation in atomic).

It is for this reason the RCU call back to delay processing was put into
place to reap threads and was, seemingly by accident, missing from
patch-2.6.17-rt7 to -rt8. That is what broke it in the first place.

I tested it with a "make -j4" which triggers the warning and it they all
go away now.

Reverse patch attached:

bill

View attachment "t.diff" of type "text/plain" (1992 bytes)