From owner-svn-src-user@FreeBSD.ORG Fri Dec 28 22:58:53 2012 Return-Path: Delivered-To: svn-src-user@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 7F7A49EB; Fri, 28 Dec 2012 22:58:53 +0000 (UTC) (envelope-from asmrookie@gmail.com) Received: from mail-la0-f53.google.com (mail-la0-f53.google.com [209.85.215.53]) by mx1.freebsd.org (Postfix) with ESMTP id BC58C8FC15; Fri, 28 Dec 2012 22:58:52 +0000 (UTC) Received: by mail-la0-f53.google.com with SMTP id fn20so1497119lab.26 for ; Fri, 28 Dec 2012 14:58:51 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:reply-to:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type; bh=FSLYK8y+0EWS0iwWDunIvjV1TDEjkOta5xcOhl2jyDk=; b=N6x855HRAfoLkDBYx41FyXREurxZpOt7drxNrDWImTGv2giZSKvDqGx0AbqnK9RYlL 65KwpvSGUDC/xw/Ila8daTO2mcwK/JM4oZ3Ckj+TUgo7ZcuS3vU3CPD6dhrXjtNk2kCF Tp0tlQNIkMk/hE9oz8+8olWbZp2HfdkSrmSBN+7O3QRIN9m2NrNt6aJBHJZaU7vIJprA 83X4a96OksjK9tkrXMsghkTOmvjbvNYfiAZrJ1pg78Paltj8hpJGfqRAFz9XZi31JE2S bziFg0iJQEXKP51rOJrSi0fw+jWblSCzGaGf8UkaJRvASulwaLY1vOtHRxMHC1gJ1gab D+sA== MIME-Version: 1.0 Received: by 10.112.14.169 with SMTP id q9mr13779536lbc.110.1356735531325; Fri, 28 Dec 2012 14:58:51 -0800 (PST) Sender: asmrookie@gmail.com Received: by 10.112.84.193 with HTTP; Fri, 28 Dec 2012 14:58:51 -0800 (PST) In-Reply-To: References: <201212282218.qBSMIfX2015054@svn.freebsd.org> Date: Fri, 28 Dec 2012 22:58:51 +0000 X-Google-Sender-Auth: 6i4TC96bfygGF2EBlpHu77AGaCI Message-ID: Subject: Re: svn commit: r244793 - in user/attilio/membarclean/dev: drm drm2 netmap virtio From: Attilio Rao To: Bryan Venteicher Content-Type: text/plain; charset=UTF-8 Cc: src-committers@freebsd.org, svn-src-user@freebsd.org X-BeenThere: svn-src-user@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list Reply-To: attilio@FreeBSD.org List-Id: "SVN commit messages for the experimental " user" src tree" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 28 Dec 2012 22:58:53 -0000 On Fri, Dec 28, 2012 at 10:43 PM, Bryan Venteicher wrote: > On Fri, Dec 28, 2012 at 4:18 PM, Attilio Rao wrote: >> Author: attilio >> Date: Fri Dec 28 22:18:41 2012 >> New Revision: 244793 >> URL: http://svnweb.freebsd.org/changeset/base/244793 >> >> Log: >> - Remove rmb() usage from netmap and replace it with intended operation >> to do actual memory fetching reads. >> - GC unused DRM_WRITEMEMORYBARRIER() from drm and drm2. >> - Use atomic_load_acq_*() in virtio and drm2 in places that don't need >> to use rmb(). >> >> All these changes remove completely rmb() from MI code, with the >> exception of cxgbe which will be hammered in a followup commit. >> >> Modified: >> user/attilio/membarclean/dev/drm/drmP.h >> user/attilio/membarclean/dev/drm2/drmP.h >> user/attilio/membarclean/dev/drm2/drm_atomic.h >> user/attilio/membarclean/dev/drm2/drm_irq.c >> user/attilio/membarclean/dev/netmap/netmap.c >> user/attilio/membarclean/dev/virtio/virtqueue.c >> >> Modified: user/attilio/membarclean/dev/drm/drmP.h >> ============================================================================== >> --- user/attilio/membarclean/dev/drm/drmP.h Fri Dec 28 22:06:50 2012 (r244792) >> +++ user/attilio/membarclean/dev/drm/drmP.h Fri Dec 28 22:18:41 2012 (r244793) >> @@ -241,11 +241,9 @@ typedef u_int32_t u32; >> typedef u_int16_t u16; >> typedef u_int8_t u8; >> >> -/* DRM_READMEMORYBARRIER() prevents reordering of reads. >> - * DRM_WRITEMEMORYBARRIER() prevents reordering of writes. >> +/* DRM_WRITEMEMORYBARRIER() prevents reordering of writes. >> * DRM_MEMORYBARRIER() prevents reordering of reads and writes. >> */ >> -#define DRM_READMEMORYBARRIER() rmb() >> #define DRM_WRITEMEMORYBARRIER() wmb() >> #define DRM_MEMORYBARRIER() mb() >> >> >> Modified: user/attilio/membarclean/dev/drm2/drmP.h >> ============================================================================== >> --- user/attilio/membarclean/dev/drm2/drmP.h Fri Dec 28 22:06:50 2012 (r244792) >> +++ user/attilio/membarclean/dev/drm2/drmP.h Fri Dec 28 22:18:41 2012 (r244793) >> @@ -263,11 +263,9 @@ typedef int32_t s32; >> typedef int16_t s16; >> typedef int8_t s8; >> >> -/* DRM_READMEMORYBARRIER() prevents reordering of reads. >> - * DRM_WRITEMEMORYBARRIER() prevents reordering of writes. >> +/* DRM_WRITEMEMORYBARRIER() prevents reordering of writes. >> * DRM_MEMORYBARRIER() prevents reordering of reads and writes. >> */ >> -#define DRM_READMEMORYBARRIER() rmb() >> #define DRM_WRITEMEMORYBARRIER() wmb() >> #define DRM_MEMORYBARRIER() mb() >> >> >> Modified: user/attilio/membarclean/dev/drm2/drm_atomic.h >> ============================================================================== >> --- user/attilio/membarclean/dev/drm2/drm_atomic.h Fri Dec 28 22:06:50 2012 (r244792) >> +++ user/attilio/membarclean/dev/drm2/drm_atomic.h Fri Dec 28 22:18:41 2012 (r244793) >> @@ -38,6 +38,7 @@ typedef u_int32_t atomic_t; >> >> #define atomic_set(p, v) (*(p) = (v)) >> #define atomic_read(p) (*(p)) >> +#define atomic_read_acq(p) atomic_load_acq_int(p) >> #define atomic_inc(p) atomic_add_int(p, 1) >> #define atomic_dec(p) atomic_subtract_int(p, 1) >> #define atomic_add(n, p) atomic_add_int(p, n) >> >> Modified: user/attilio/membarclean/dev/drm2/drm_irq.c >> ============================================================================== >> --- user/attilio/membarclean/dev/drm2/drm_irq.c Fri Dec 28 22:06:50 2012 (r244792) >> +++ user/attilio/membarclean/dev/drm2/drm_irq.c Fri Dec 28 22:18:41 2012 (r244793) >> @@ -701,8 +701,7 @@ u32 drm_vblank_count_and_time(struct drm >> do { >> cur_vblank = atomic_read(&dev->_vblank_count[crtc]); >> *vblanktime = vblanktimestamp(dev, crtc, cur_vblank); >> - rmb(); >> - } while (cur_vblank != atomic_read(&dev->_vblank_count[crtc])); >> + } while (cur_vblank != atomic_read_acq(&dev->_vblank_count[crtc])); >> >> return cur_vblank; >> } >> >> Modified: user/attilio/membarclean/dev/netmap/netmap.c >> ============================================================================== >> --- user/attilio/membarclean/dev/netmap/netmap.c Fri Dec 28 22:06:50 2012 (r244792) >> +++ user/attilio/membarclean/dev/netmap/netmap.c Fri Dec 28 22:18:41 2012 (r244793) >> @@ -98,6 +98,9 @@ MALLOC_DEFINE(M_NETMAP, "netmap", "Netwo >> #include >> #include >> >> +#define MEMFETCH(var) \ >> + (__DEVOLATILE(__typeof(var), *((volatile __typeof(var) *)&var))) >> + >> u_int netmap_total_buffers; >> u_int netmap_buf_size; >> char *netmap_buffer_base; /* address of an invalid buffer */ >> @@ -1081,10 +1084,7 @@ error: >> error = ENXIO; >> break; >> } >> - rmb(); /* make sure following reads are not from cache */ >> - >> - >> - ifp = priv->np_ifp; /* we have a reference */ >> + ifp = MEMFETCH(priv->np_ifp); >> >> if (ifp == NULL) { >> D("Internal error: nifp != NULL && ifp == NULL"); >> @@ -1194,9 +1194,7 @@ netmap_poll(struct cdev *dev, int events >> D("No if registered"); >> return POLLERR; >> } >> - rmb(); /* make sure following reads are not from cache */ >> - >> - ifp = priv->np_ifp; >> + ifp = MEMFETCH(priv->np_ifp); >> // XXX check for deleting() ? >> if ( (ifp->if_capenable & IFCAP_NETMAP) == 0) >> return POLLERR; >> >> Modified: user/attilio/membarclean/dev/virtio/virtqueue.c >> ============================================================================== >> --- user/attilio/membarclean/dev/virtio/virtqueue.c Fri Dec 28 22:06:50 2012 (r244792) >> +++ user/attilio/membarclean/dev/virtio/virtqueue.c Fri Dec 28 22:18:41 2012 (r244793) >> @@ -525,8 +525,7 @@ virtqueue_dequeue(struct virtqueue *vq, >> used_idx = vq->vq_used_cons_idx++ & (vq->vq_nentries - 1); >> uep = &vq->vq_ring.used->ring[used_idx]; >> >> - rmb(); >> - desc_idx = (uint16_t) uep->id; >> + desc_idx = (uint16_t)atomic_load_acq_32(&uep->id); >> if (len != NULL) >> *len = uep->len; >> > > VirtIO uses 16-bit fields which makes it hard to adapt to MI > atomic(9). The field here happens to be 32-bits, but that is for > alignment purposes. I have a patch from a couple months back that > switches VirtIO to atomic_*(), but the mb()'s are still #ifdef in > there for the eventual support of arch's without 16-bit atomic(9) (and > the patch needs a bit of followup work). I think you are referring to the wmb() usage. However, right now we don't guarantee _8 and _16 atomic ops on every architecture and we should stay that way. This means that even if you introduce the _16 variant for all the architecture this is not enough to yet use it in virtio. I have a couple of ideas on how to fix the wmb() one, I will send you an e-mail when I get to it. Attilio -- Peace can only be achieved by understanding - A. Einstein