Re: Cheap lock for user mode processes release when process exits

[Andrew Morton]

On Fri, 13 Apr 2007 01:54:28 +0000 (GMT) <mchu@xxxxxxxxxxxxx> wrote:

> Hi all,
> 
> Maybe someone here knows better.
> 
> I have several user-mode processes using shared mmap.  There can be several reader processes and only one writer.  Readers access the shared region frequently, writer seldom.
> 
> Naturally, multi-reader/single-writer locks works best.  I tried this with futex on 2.6.9-42.EL.  However, if one of the processes is killed/exits, the lock doesn't get released.
> 
> I can trap the signal to release the lock, but not all signals like kill.
> 
> Anyway I can achieve this without a potential deadlock?
> 

Robust futexes: http://lwn.net/Articles/172149/

But I don't know whether RH backported them into RHEL4.
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