linux-kernel - Re: [RFC][PATCH 4/7] lockdep: Seperate lock ids for read/write acquires

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:	Tue, 19 Apr 2011 00:07:00 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Gautham R Shenoy <gautshen@....ac.in>
Subject: Re: [RFC][PATCH 4/7] lockdep: Seperate lock ids for read/write
 acquires

On Sun, 2011-04-17 at 11:45 +0200, Peter Zijlstra wrote:
> In order to support recursive read locks we need to support the
> previously mentioned lock state conflict matrix:
> 
>  Conflicting_states(WRITE):             RECURSIVE_READ | READ | WRITE
>  Conflicting_states(READ):                               READ | WRITE
>  Conflicting_states(RECURSIVE_READ):                            WRITE
> 
> Since this introduces asymmetry between recursive read and write, we
> need to split the lock dependency chains such that we can traverse
> WRITE chains without observing RECURSIVE_READ|READ chains. 

So while we split off the WRITE chain from the RECURSIVE_READ|READ
chains, shouldn't we split it in three, because the READ conflict state
only has READ|WRITE, not RECURSIVE_READ.

Therefore a RECURSIVE_READ dependency in the READ chain could throw the
regular READ cycle detector, no?


 A(r) -> B(r) -> C(rr)

 C(w) -> B(r)

would close the cycle and report a problem, but doesn't match the
conflict states.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/