From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2EBB6ECDFB8 for ; Wed, 18 Jul 2018 02:19:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 98A062075C for ; Wed, 18 Jul 2018 02:19:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 98A062075C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731382AbeGRCzH (ORCPT ); Tue, 17 Jul 2018 22:55:07 -0400 Received: from szxga07-in.huawei.com ([45.249.212.35]:53412 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730180AbeGRCzH (ORCPT ); Tue, 17 Jul 2018 22:55:07 -0400 Received: from DGGEMS405-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 27B625E12E315; Wed, 18 Jul 2018 10:19:34 +0800 (CST) Received: from [10.177.253.249] (10.177.253.249) by smtp.huawei.com (10.3.19.205) with Microsoft SMTP Server id 14.3.382.0; Wed, 18 Jul 2018 10:19:33 +0800 Subject: Re: [PATCH v2] net/9p/client.c: fix misuse of spin_lock_irqsave for p9_client lock To: Dominique Martinet References: <5B4D8BD8.3040009@huawei.com> <20180717115639.GA26901@nautica> CC: Eric Van Hensbergen , Ron Minnich , Latchesar Ionkov , Linux Kernel Mailing List , From: piaojun Message-ID: <5B4EA3A8.5090004@huawei.com> Date: Wed, 18 Jul 2018 10:19:20 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <20180717115639.GA26901@nautica> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.253.249] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Dominique, On 2018/7/17 19:56, Dominique Martinet wrote: > piaojun wrote on Tue, Jul 17, 2018: >> In p9_read_work(), we use spin_lock for client->lock, but misuse >> spin_lock_irqsave for it in p9_fid_create(). As p9_client lock won't be >> locked in irq context, so spin_lock is enough. And that will improve the >> performance. > > (I didn't say in v1, but the commit message sounds a bit odd to me, if > there is any other change to the patch could you please rephrase it a > bit?) Yes, I will rephrase it if there is any change to the patch. > >> Rebased on 9p-next. > > (Likewise, this should probably go below the '---' mark to not be in the > final commit message, 9p-next does not make sense to linux as a whole) > Thanks for your suggestion. >> >> Signed-off-by: Jun Piao > > Nitpicks aside this still looks good to me, I'm not expert in locking > but I believe the conn_cancel stuff in trans_fd is called either from > user context or workqueue which also is process context, while the rest > comes from user context only. > > There *are* common functions called from interrupt context (I see: > p9_tag_lookup, p9_client_cb, p9_parse_header) but luckily enough > none of these take the lock. > > I'll give this one a little bit of time for others to review before > picking it up, just in case, but will do if no-one complains. > >> --- >> net/9p/client.c | 18 ++++++++---------- >> net/9p/trans_fd.c | 7 +++---- >> 2 files changed, 11 insertions(+), 14 deletions(-) >> >> diff --git a/net/9p/client.c b/net/9p/client.c >> index 30f9aee..f6897ee 100644 >> --- a/net/9p/client.c >> +++ b/net/9p/client.c >> @@ -275,14 +275,14 @@ static struct p9_fcall *p9_fcall_alloc(int alloc_msize) >> INIT_LIST_HEAD(&req->req_list); >> >> idr_preload(GFP_NOFS); >> - spin_lock_irq(&c->lock); >> + spin_lock(&c->lock); >> if (type == P9_TVERSION) >> tag = idr_alloc(&c->reqs, req, P9_NOTAG, P9_NOTAG + 1, >> GFP_NOWAIT); >> else >> tag = idr_alloc(&c->reqs, req, 0, P9_NOTAG, GFP_NOWAIT); >> req->tc->tag = tag; >> - spin_unlock_irq(&c->lock); >> + spin_unlock(&c->lock); >> idr_preload_end(); >> if (tag < 0) >> goto free; >> @@ -328,13 +328,12 @@ struct p9_req_t *p9_tag_lookup(struct p9_client *c, u16 tag) >> */ >> static void p9_free_req(struct p9_client *c, struct p9_req_t *r) >> { >> - unsigned long flags; >> u16 tag = r->tc->tag; >> >> p9_debug(P9_DEBUG_MUX, "clnt %p req %p tag: %d\n", c, r, tag); >> - spin_lock_irqsave(&c->lock, flags); >> + spin_lock(&c->lock); >> idr_remove(&c->reqs, tag); >> - spin_unlock_irqrestore(&c->lock, flags); >> + spin_unlock(&c->lock); >> kfree(r->tc); >> kfree(r->rc); >> kmem_cache_free(p9_req_cache, r); >> @@ -846,10 +845,10 @@ static struct p9_fid *p9_fid_create(struct p9_client *clnt) >> fid->fid = 0; >> >> idr_preload(GFP_KERNEL); >> - spin_lock_irq(&clnt->lock); >> + spin_lock(&clnt->lock); >> ret = idr_alloc_u32(&clnt->fids, fid, &fid->fid, P9_NOFID - 1, >> GFP_NOWAIT); >> - spin_unlock_irq(&clnt->lock); >> + spin_unlock(&clnt->lock); >> idr_preload_end(); >> >> if (!ret) >> @@ -862,13 +861,12 @@ static struct p9_fid *p9_fid_create(struct p9_client *clnt) >> static void p9_fid_destroy(struct p9_fid *fid) >> { >> struct p9_client *clnt; >> - unsigned long flags; >> >> p9_debug(P9_DEBUG_FID, "fid %d\n", fid->fid); >> clnt = fid->clnt; >> - spin_lock_irqsave(&clnt->lock, flags); >> + spin_lock(&clnt->lock); >> idr_remove(&clnt->fids, fid->fid); >> - spin_unlock_irqrestore(&clnt->lock, flags); >> + spin_unlock(&clnt->lock); >> kfree(fid->rdir); >> kfree(fid); >> } >> diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c >> index bf459ee..94ef685 100644 >> --- a/net/9p/trans_fd.c >> +++ b/net/9p/trans_fd.c >> @@ -197,15 +197,14 @@ static void p9_mux_poll_stop(struct p9_conn *m) >> static void p9_conn_cancel(struct p9_conn *m, int err) >> { >> struct p9_req_t *req, *rtmp; >> - unsigned long flags; >> LIST_HEAD(cancel_list); >> >> p9_debug(P9_DEBUG_ERROR, "mux %p err %d\n", m, err); >> >> - spin_lock_irqsave(&m->client->lock, flags); >> + spin_lock(&m->client->lock); >> >> if (m->err) { >> - spin_unlock_irqrestore(&m->client->lock, flags); >> + spin_unlock(&m->client->lock); >> return; >> } >> >> @@ -217,7 +216,7 @@ static void p9_conn_cancel(struct p9_conn *m, int err) >> list_for_each_entry_safe(req, rtmp, &m->unsent_req_list, req_list) { >> list_move(&req->req_list, &cancel_list); >> } >> - spin_unlock_irqrestore(&m->client->lock, flags); >> + spin_unlock(&m->client->lock); >> >> list_for_each_entry_safe(req, rtmp, &cancel_list, req_list) { >> p9_debug(P9_DEBUG_ERROR, "call back req %p\n", req); >> -- >