From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-870783-1520357720-2-1725398618340640004 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='198.145.29.99', Host='mail.kernel.org', Country='US', FromHeader='org', MailFrom='org' X-Spam-charsets: X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: SRS0=gsCl=F4=gmail.com=htejun@kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1520357719; b=daaXasYXV9rhHmKnGR5Kn5GitMiqQnXg1Th2JzrTdOCKk4R kLmyA6YJL2UtDzMzZ2i1dGHDHasSIIoFRc12KeDIWjETXfMOqU+e9YRxctY/ivF9 3XJ+QcSv2CY5s0yTuHrxkUebYNg9/jSFbfraH0Ifpl+cWs+F1S5d7/a6Xew9IQ3X 1zYNfFyVfORZl8OsndW8t2HWtWDr3NFI+/PpiLibgEwg1gTmQxpNQpNQCnUnw945 GdKjYw+sLY/Px8elUZGwQ23nad/LT0ACyq1T7rvCkA/E01E5ys/XQ3H6aXRPo9DC zUJGlvLMyDs/elN5XJRRKESTXVfA6bg0l0hSF7A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=sender:from:to:cc:subject:date:message-id :in-reply-to:references; s=arctest; t=1520357719; bh=AnhtS6EV7vG wicWnJ1Jq18HmGBzG/qLrYzc0e+f+bP8=; b=fENpaSOywkkSBF6/89NugCkmhJ8 fttWWTitb2wLnD5lpDvN06sSx0rMhj3KEzoKYx9m/B1U0cMH1y1Q1PMWhSSRzUU6 IH96IfvlTA/+7u+Fxr3B4PLK7rSapHa8vW/D+cGf/VoVjSFuW+k0kDK4+wqQDZMy bpJqaiZMuEsJ8EV+XQs0vp3sjNIFch1t9gPqKGP7iKw/pCJi6/yxzNAcwmz8/8h6 iZZyMIgGztzSJamyCLNr4iX4khycgFXNlg//r8DaA6bDYlrqus+SShJqNU7B4CuY aB0gQqVaplY9wm5Bt1/R8S7hS7F2lTqpSgt+be2WeAQZQocsoNUPRfSpVXA== ARC-Authentication-Results: i=1; mx4.messagingengine.com; arc=none (no signatures found); dkim=pass (2048-bit rsa key sha256) header.d=gmail.com header.i=@gmail.com header.b=hkfv96eJ x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=20161025; dmarc=none (p=none,d=none) header.from=kernel.org; iprev=pass policy.iprev=198.145.29.99 (mail.kernel.org); spf=none smtp.mailfrom=SRS0=gsCl=F4=gmail.com=htejun@kernel.org smtp.helo=mail.kernel.org; x-aligned-from=domain_pass; x-category=clean score=-100 state=0; x-google-dkim=pass (2048-bit rsa key) header.d=1e100.net header.i=@1e100.net header.b=ra6KsUfG; x-ptr=pass x-ptr-helo=mail.kernel.org x-ptr-lookup=mail.kernel.org; x-return-mx=pass smtp.domain=kernel.org smtp.result=pass smtp_is_org_domain=yes header.domain=kernel.org header.result=pass header_is_org_domain=yes; x-tls=pass version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128 Authentication-Results: mx4.messagingengine.com; arc=none (no signatures found); dkim=pass (2048-bit rsa key sha256) header.d=gmail.com header.i=@gmail.com header.b=hkfv96eJ x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=20161025; dmarc=none (p=none,d=none) header.from=kernel.org; iprev=pass policy.iprev=198.145.29.99 (mail.kernel.org); spf=none smtp.mailfrom=SRS0=gsCl=F4=gmail.com=htejun@kernel.org smtp.helo=mail.kernel.org; x-aligned-from=domain_pass; x-category=clean score=-100 state=0; x-google-dkim=pass (2048-bit rsa key) header.d=1e100.net header.i=@1e100.net header.b=ra6KsUfG; x-ptr=pass x-ptr-helo=mail.kernel.org x-ptr-lookup=mail.kernel.org; x-return-mx=pass smtp.domain=kernel.org smtp.result=pass smtp_is_org_domain=yes header.domain=kernel.org header.result=pass header_is_org_domain=yes; x-tls=pass version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128 X-Remote-Delivered-To: security@kernel.org DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 802B420856 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=htejun@gmail.com X-Google-Smtp-Source: AG47ELt+VeHe4He6oK4vCMP0KjPAotv3w8yzN50BhObbV1W1IiavUvNQh8VS/MEa72Wx8vyomVYd0Q== Sender: Tejun Heo From: Tejun Heo To: torvalds@linux-foundation.org, jannh@google.com, paulmck@linux.vnet.ibm.com, bcrl@kvack.org, viro@zeniv.linux.org.uk, kent.overstreet@gmail.com Cc: security@kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, Tejun Heo , Bart Van Assche , Jens Axboe Subject: [PATCH 5/7] block: Remove superflous rcu_read_[un]lock_sched() in blk_queue_enter() Date: Tue, 6 Mar 2018 09:33:14 -0800 Message-Id: <20180306173316.3088458-5-tj@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20180306173316.3088458-1-tj@kernel.org> References: <20180306172657.3060270-1-tj@kernel.org> <20180306173316.3088458-1-tj@kernel.org> X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 3a0a529971ec ("block, scsi: Make SCSI quiesce and resume work reliably") added rcu_read_[un]lock_sched() to blk_queue_enter() along with other changes but it doesn't seem to be doing anything. blk_queue_enter() is called with @q - the pointer to the target request_queue, so the caller obviously has to guarantee that @q can be dereferenced, and inside the RCU-sched protected area, there's nothing which needs further protection. Let's remove the superflous rcu_read_[un]lock_sched(). Signed-off-by: Tejun Heo Cc: Bart Van Assche Cc: Jens Axboe Cc: Linus Torvalds --- Hello, Bart. This came up while auditing percpu_ref users for problematic RCU usages. I couldn't understand what the RCU protection was doing. It'd be great if you can take a look and tell me whether I missed something. Thanks. block/blk-core.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index 6d82c4f..e3b4d1849 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -827,7 +827,6 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags) bool success = false; int ret; - rcu_read_lock_sched(); if (percpu_ref_tryget_live(&q->q_usage_counter)) { /* * The code that sets the PREEMPT_ONLY flag is @@ -840,7 +839,6 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags) percpu_ref_put(&q->q_usage_counter); } } - rcu_read_unlock_sched(); if (success) return 0; -- 2.9.5