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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 2 Apr 2019 16:23:30 +0100 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp23034.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x32FNTTq13435078 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 2 Apr 2019 15:23:29 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 60219B2066; Tue, 2 Apr 2019 15:23:29 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4A7B6B2067; Tue, 2 Apr 2019 15:23:29 +0000 (GMT) Received: from paulmck-ThinkPad-W541 (unknown [9.70.82.188]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Tue, 2 Apr 2019 15:23:29 +0000 (GMT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id 7174016C2A40; Tue, 2 Apr 2019 08:23:34 -0700 (PDT) Date: Tue, 2 Apr 2019 08:23:34 -0700 From: "Paul E. McKenney" To: Mathieu Desnoyers Cc: rcu@vger.kernel.org, linux-kernel , Ingo Molnar , Lai Jiangshan , dipankar , Andrew Morton , Josh Triplett , Thomas Gleixner , Peter Zijlstra , rostedt , David Howells , Eric Dumazet , fweisbec , Oleg Nesterov , "Joel Fernandes, Google" , linux-nvdimm@lists.01.org, dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org Subject: Re: [PATCH RFC tip/core/rcu 0/4] Forbid static SRCU use in modules Reply-To: paulmck@linux.ibm.com References: <20190402142816.GA13084@linux.ibm.com> <886051277.1395.1554218080591.JavaMail.zimbra@efficios.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <886051277.1395.1554218080591.JavaMail.zimbra@efficios.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 19040215-0068-0000-0000-000003AF7936 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010862; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000284; SDB=6.01183302; UDB=6.00619488; IPR=6.00964050; MB=3.00026261; MTD=3.00000008; XFM=3.00000015; UTC=2019-04-02 15:23:35 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19040215-0069-0000-0000-000048049FEC Message-Id: <20190402152334.GC4102@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-04-02_05:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=718 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1904020103 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 02, 2019 at 11:14:40AM -0400, Mathieu Desnoyers wrote: > ----- On Apr 2, 2019, at 10:28 AM, paulmck paulmck@linux.ibm.com wrote: > > > Hello! > > > > This series prohibits use of DEFINE_SRCU() and DEFINE_STATIC_SRCU() > > by loadable modules. The reason for this prohibition is the fact > > that using these two macros within modules requires that the size of > > the reserved region be increased, which is not something we want to > > be doing all that often. Instead, loadable modules should define an > > srcu_struct and invoke init_srcu_struct() from their module_init function > > and cleanup_srcu_struct() from their module_exit function. Note that > > modules using call_srcu() will also need to invoke srcu_barrier() from > > their module_exit function. > > This arbitrary API limitation seems weird. > > Isn't there a way to allow modules to use DEFINE_SRCU and DEFINE_STATIC_SRCU > while implementing them with dynamic allocation under the hood ? Although call_srcu() already has initialization hooks, some would also be required in srcu_read_lock(), and I am concerned about adding memory allocation at that point, especially given the possibility of memory-allocation failure. And the possibility that the first srcu_read_lock() happens in an interrupt handler or similar. Or am I missing a trick here? Thanx, Paul > Thanks, > > Mathieu > > > > > > This series consist of the following: > > > > 1. Dynamically allocate dax_srcu. > > > > 2. Dynamically allocate drm_unplug_srcu. > > > > 3. Dynamically allocate kfd_processes_srcu. > > > > These build and have been subjected to 0day testing, but might also need > > testing by someone having the requisite hardware. > > > > Thanx, Paul > > > > ------------------------------------------------------------------------ > > > > drivers/dax/super.c | 10 +++++- > > drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c | 5 +++ > > drivers/gpu/drm/amd/amdkfd/kfd_process.c | 2 - > > drivers/gpu/drm/drm_drv.c | 8 ++++ > > include/linux/srcutree.h | 19 +++++++++-- > > kernel/rcu/rcuperf.c | 40 +++++++++++++++++++----- > > kernel/rcu/rcutorture.c | 48 +++++++++++++++++++++-------- > > 7 files changed, 105 insertions(+), 27 deletions(-) > > -- > Mathieu Desnoyers > EfficiOS Inc. > http://www.efficios.com >