linux-kernel - Re: [RFC] NUMA futex hashing

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, 8 Aug 2006 14:29:44 +0200
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Andi Kleen <ak@...e.de>
Cc:	Ravikiran G Thirumalai <kiran@...lex86.org>,
	"Shai Fultheim (Shai@...lex86.org)" <shai@...lex86.org>,
	pravin b shelar <pravin.shelar@...softinc.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC] NUMA futex hashing

On Tuesday 08 August 2006 12:36, Andi Kleen wrote:
> > We may have special case for PRIVATE futexes (they dont need to be
> > chained in a global table, but a process private table)
>
> What do you mean with PRIVATE futex?
>
> Even if the futex mapping is only visible by a single MM mmap_sem is still
> needed to protect against other threads doing mmap.

Hum... I would call that a user error.

If a thread is munmap()ing the vma that contains active futexes, result is 
undefined. Same as today I think (a thread blocked in a FUTEX_WAIT should 
stay blocked)

The point is that private futexes could be managed using virtual addresses, 
and no call to find_extend_vma(), hence no mmap_sem contention.

There could be problem if the same futex (32 bits integer) could be mapped at 
different virtual addresses in the same process.

Eric
-
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/