From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Wilcox Date: Mon, 04 Feb 2019 13:42:03 +0000 Subject: Re: [PATCH] mm/hmm: potential deadlock in nonblocking code Message-Id: <20190204134203.GB21860@bombadil.infradead.org> List-Id: References: <20190204132043.GA16485@kadam> In-Reply-To: <20190204132043.GA16485@kadam> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Dan Carpenter Cc: =?iso-8859-1?B?Suly9G1l?= Glisse , linux-mm@kvack.org, kernel-janitors@vger.kernel.org, Andrew Morton , Stephen Rothwell On Mon, Feb 04, 2019 at 04:20:44PM +0300, Dan Carpenter wrote: > > - if (!nrange->blockable && !mutex_trylock(&hmm->lock)) { > - ret = -EAGAIN; > - goto out; > + if (!nrange->blockable) { > + if (!mutex_trylock(&hmm->lock)) { > + ret = -EAGAIN; > + goto out; > + } > } else > mutex_lock(&hmm->lock); I think this would be more readable written as: ret = -EAGAIN; if (nrange->blockable) mutex_lock(&hmm->lock); else if (!mutex_trylock(&hmm->lock)) goto out; but it'll be up to Jerome. 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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id b30si87807pla.285.2019.02.04.05.42.05 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 04 Feb 2019 05:42:05 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=bUnzJi0H; spf=pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=willy@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=NSzXV8ZhnHo67p2jZfhA01o+VR5IxF6NSFWwjcl9vBs=; b=bUnzJi0HT/ox8NGH24iKpoHBI xG4ses5V0Mn7w4vkiSQmd5Rqs5J3C8QHKSyv8rFLvP0evF3kNQx17HrKPJnppfheNZ+ahjBByzIER jJnf4d5ty0ueeZQle7TabyGqk5cfAFkMDZrXKHzLqNsSjKsfrSISbEq09jBjfICBnJOjORwkkjPb3 Dp0rNRLAxNvJwFD/1baFqIQgJ+EpmnXcujd3yIzj5f9qPnVaTu3hviNOlnvaFz/nH+Tqw5zfTUGvb U9bPRQ773d4DyI1r+4EEeKjr4mhRrmPh4BUC5W0dctXkrHGRXEN6v5Q44hciYzE3z3mdHDDP8mwS2 Qpg+dF+Sg==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gqeVf-00088t-R1; Mon, 04 Feb 2019 13:42:03 +0000 Date: Mon, 4 Feb 2019 05:42:03 -0800 From: Matthew Wilcox To: Dan Carpenter Cc: =?iso-8859-1?B?Suly9G1l?= Glisse , linux-mm@kvack.org, kernel-janitors@vger.kernel.org, Andrew Morton , Stephen Rothwell Subject: Re: [PATCH] mm/hmm: potential deadlock in nonblocking code Message-ID: <20190204134203.GB21860@bombadil.infradead.org> References: <20190204132043.GA16485@kadam> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190204132043.GA16485@kadam> User-Agent: Mutt/1.9.2 (2017-12-15) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Feb 04, 2019 at 04:20:44PM +0300, Dan Carpenter wrote: > > - if (!nrange->blockable && !mutex_trylock(&hmm->lock)) { > - ret = -EAGAIN; > - goto out; > + if (!nrange->blockable) { > + if (!mutex_trylock(&hmm->lock)) { > + ret = -EAGAIN; > + goto out; > + } > } else > mutex_lock(&hmm->lock); I think this would be more readable written as: ret = -EAGAIN; if (nrange->blockable) mutex_lock(&hmm->lock); else if (!mutex_trylock(&hmm->lock)) goto out; but it'll be up to Jerome.