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[140.211.169.12]) by mx.google.com with ESMTPS id y7si3060205pgj.274.2019.04.18.15.24.32 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Apr 2019 15:24:32 -0700 (PDT) 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 584911F5A; Thu, 18 Apr 2019 22:24:32 +0000 (UTC) Date: Thu, 18 Apr 2019 15:24:31 -0700 From: Andrew Morton To: Matthew Wilcox Cc: Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, Johannes Weiner , Vlastimil Babka , Roman Gushchin , Christoph Hellwig , Joel Fernandes Subject: Re: [PATCH v4 1/2] mm: refactor __vunmap() to avoid duplicated call to find_vm_area() Message-Id: <20190418152431.c583ef892a8028c662db3e6a@linux-foundation.org> In-Reply-To: <20190418111834.GE7751@bombadil.infradead.org> References: <20190417194002.12369-1-guro@fb.com> <20190417194002.12369-2-guro@fb.com> <20190417145827.8b1c83bf22de8ba514f157e3@linux-foundation.org> <20190418111834.GE7751@bombadil.infradead.org> X-Mailer: Sylpheed 3.7.0 (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 Thu, 18 Apr 2019 04:18:34 -0700 Matthew Wilcox wrote: > On Wed, Apr 17, 2019 at 02:58:27PM -0700, Andrew Morton wrote: > > On Wed, 17 Apr 2019 12:40:01 -0700 Roman Gushchin wrote: > > > +static struct vm_struct *__remove_vm_area(struct vmap_area *va) > > > +{ > > > + struct vm_struct *vm = va->vm; > > > + > > > + might_sleep(); > > > > Where might __remove_vm_area() sleep? > > > > >From a quick scan I'm only seeing vfree(), and that has the > > might_sleep_if(!in_interrupt()). > > > > So perhaps we can remove this... > > See commit 5803ed292e63 ("mm: mark all calls into the vmalloc subsystem as potentially sleeping") > > It looks like the intent is to unconditionally check might_sleep() at > the entry points to the vmalloc code, rather than only catch them in > the occasional place where it happens to go wrong. afaict, vfree() will only do a mutex_trylock() in try_purge_vmap_area_lazy(). So does vfree actually sleep in any situation? Whether or not local interrupts are enabled?