linux-kernel - Re: [PATCH v8 15/19] locking/rwsem: Adaptive disabling of reader optimistic spinning

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:   Wed, 5 Jun 2019 22:19:01 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Ingo Molnar <mingo@...hat.com>, Will Deacon <will.deacon@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        x86@...nel.org, Davidlohr Bueso <dave@...olabs.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        huang ying <huang.ying.caritas@...il.com>
Subject: Re: [PATCH v8 15/19] locking/rwsem: Adaptive disabling of reader
 optimistic spinning

On Wed, Jun 05, 2019 at 02:13:27PM -0400, Waiman Long wrote:

> Using cmpxchg_double is actually more risky than I thought. I have been
> trying to try to use cmpxchg_double for down_write, but I kept getting
> kernel panics because the rwsem wasn't 16b-aligned. As rwsem is embedded
> in quite a large number of structures, they all have to align properly
> to make that work or the kernel will panic. That does seem too risky to
> me. So I am dropping the idea of trying to use it.

Urgh, that's another things that's been on the TODO list for a long long
time, write code to verify the alignment of allocations :/ I'm
suspecting quite a lot of that goes wrong all over the place.