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[140.211.169.12]) by mx.google.com with ESMTPS id 37si36011576pgw.590.2019.01.29.17.01.52 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 29 Jan 2019 17:01:52 -0800 (PST) Received-SPF: pass (google.com: domain of akpm@linux-foundation.org designates 140.211.169.12 as permitted sender) client-ip=140.211.169.12; Authentication-Results: mx.google.com; spf=pass (google.com: domain of akpm@linux-foundation.org designates 140.211.169.12 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org Received: from akpm3.svl.corp.google.com (unknown [104.133.8.65]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 942E73230; Wed, 30 Jan 2019 01:01:51 +0000 (UTC) Date: Tue, 29 Jan 2019 17:01:50 -0800 From: Andrew Morton To: Tetsuo Handa Cc: Yang Shi , Jiufei Xue , Linux MM , joseph.qi@linux.alibaba.com, Linus Torvalds Subject: Re: [PATCH] mm: fix sleeping function warning in alloc_swap_info Message-Id: <20190129170150.57021080bdfd3a46a479d45d@linux-foundation.org> In-Reply-To: <201901300042.x0U0g6EH085874@www262.sakura.ne.jp> References: <201901300042.x0U0g6EH085874@www262.sakura.ne.jp> X-Mailer: Sylpheed 3.6.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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 Wed, 30 Jan 2019 09:42:06 +0900 Tetsuo Handa wrote: > > > > > > If we want to allow vfree() to sleep, at least we need to test with > > > kvmalloc() == vmalloc() (i.e. force kvmalloc()/kvfree() users to use > > > vmalloc()/vfree() path). For now, reverting the > > > "Context: Either preemptible task context or not-NMI interrupt." change > > > will be needed for stable kernels. > > > > So, the comment for vfree "May sleep if called *not* from interrupt > > context." is wrong? > > Commit bf22e37a641327e3 ("mm: add vfree_atomic()") says > > We are going to use sleeping lock for freeing vmap. However some > vfree() users want to free memory from atomic (but not from interrupt) > context. For this we add vfree_atomic() - deferred variation of vfree() > which can be used in any atomic context (except NMIs). > > and commit 52414d3302577bb6 ("kvfree(): fix misleading comment") made > > - * Context: Any context except NMI. > + * Context: Either preemptible task context or not-NMI interrupt. > > change. But I think that we converted kmalloc() to kvmalloc() without checking > context of kvfree() callers. Therefore, I think that kvfree() needs to use > vfree_atomic() rather than just saying "vfree() might sleep if called not in > interrupt context."... Whereabouts in the vfree() path can the kernel sleep?