From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Gleixner Subject: Re: [PATCH 1/3] posix timers: Allocate timer id per process (v2) Date: Fri, 8 Mar 2013 13:50:28 +0100 (CET) Message-ID: References: <512665BA.9040802@parallels.com> <512665E1.4040800@parallels.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Return-path: In-Reply-To: <512665E1.4040800-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Pavel Emelyanov Cc: Ingo Molnar , Peter Zijlstra , Michael Kerrisk , Matthew Helsley , linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Linux Kernel Mailing List List-Id: linux-api@vger.kernel.org Pavel, On Thu, 21 Feb 2013, Pavel Emelyanov wrote: > Patch replaces global idr with global hash table for posix timers and > makes timer ids unique not globally, but per process. Next free timer id is > type of integer and stored on signal struct (posix_timer_id). If free timer > id reaches negative value on timer creation, it will be dropped to zero and > -EAGAIN will be returned to user. > > Hash table has 512 slots. > Key is constructed as follows: > key = hash_32(hash_32(current->signal) ^ posix_timer_id)); > > Note: with this patch, id, returned to user, is not the minimal free > amymore. It means, that id, returned to user space in loop, listed below, > will be increasing on each iteration till INT_MAX and then dropped to zero: > > while(1) { > id = timer_create(...); > timer_delete(id); > } > > In this version the helpers from include/linux/hashtable.h are used > instead of hand-made hash-table. I think the patches are ready to go, though the changelog needs quite some care. It's explaining what the patch does and not why. Can you please rework? Thanks, tglx