linux-kernel - Re: [PATCH v2] kmemleak: Turn kmemleak

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:   Fri, 23 Nov 2018 12:06:11 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Andrea Parri <andrea.parri@...rulasolutions.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     zhe.he@...driver.com, catalin.marinas@....com, tglx@...utronix.de,
        rostedt@...dmis.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
        boqun.feng@...il.com
Subject: Re: [PATCH v2] kmemleak: Turn kmemleak_lock to raw spinlock on RT

On 2018-11-23 12:02:55 [+0100], Andrea Parri wrote:
> > is this an RT-only problem? Because mainline should not allow read->read
> > locking or read->write locking for reader-writer locks. If this only
> > happens on v4.18 and not on v4.19 then something must have fixed it.
> 
> Probably misunderstanding, but I'd say that read->read locking is "the
> norm"...?
> 
> If you don't use qrwlock, readers are also "recursive", in part.,
> 
>   P0			P1
>   read_lock(l)
> 			write_lock(l)
>   read_lock(l)
> 
> won't block P0 on the second read_lock().  (qrwlock somehow complicate
> the analysis; IIUC, they are recursive if and only if in_interrupt().).

ehm, peterz, is that true? My memory on that is that all readers will
block if there is a writer pending.

>   Andrea

Sebastian