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[209.85.220.65]) by mx.google.com with SMTPS id t20sor214947lfl.17.2019.06.07.13.57.20 for (Google Transport Security); Fri, 07 Jun 2019 13:57:20 -0700 (PDT) Received-SPF: pass (google.com: domain of jrdr.linux@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=QNjqqGcb; spf=pass (google.com: domain of jrdr.linux@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=jrdr.linux@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Tny04mc/baghyNAFbwqZ/oFPlAWsvuYVsFUjkQqS22Q=; b=QNjqqGcbdGS6ZZ8Py7DrJaDT7cFcTNRm3NFiWdMD9IiJe7FR81nCaS4ldYhjYQaa3x pDZ5dtaQh4VtXRU/M4vMtz6V86TMfvWqfIOv3+xQ1BS3Pi/OO8O34PrdybxezwGLFnCA 796+BWV1HccLI+fGw5gqheajIrNxGca1f6Uv38w0SnJb21LsBYtuvkgZh+7P53Wem6Jj v1LkfYLNkunt2AZr9uAea0s8kIG7tfsuyXHc6LOsqr0UjKu/sKW1okPNjSls4KDZ0RxL AyfSU2pULwfpv2onwyxRS9I+M50aNUxdHUI7kSVEx7UEAZ1INmBowgvS78Dnkqo8S+cx zMQw== X-Google-Smtp-Source: APXvYqxZe1mVzQxPGczygMJ7Uvjoz9hw+fjkiPEv98As/XW3kebMuog/DbkAruQO2q5Tc4hMSjsxYVTQBupk3BZEUnY= X-Received: by 2002:ac2:4ac5:: with SMTP id m5mr4395351lfp.95.1559941039830; Fri, 07 Jun 2019 13:57:19 -0700 (PDT) MIME-Version: 1.0 References: <20190523153436.19102-1-jgg@ziepe.ca> <20190523153436.19102-9-jgg@ziepe.ca> <20190607193955.GT14802@ziepe.ca> In-Reply-To: <20190607193955.GT14802@ziepe.ca> From: Souptick Joarder Date: Sat, 8 Jun 2019 02:32:23 +0530 Message-ID: Subject: Re: [RFC PATCH 08/11] mm/hmm: Use lockdep instead of comments To: Jason Gunthorpe Cc: linux-rdma@vger.kernel.org, Linux-MM , Jerome Glisse , Ralph Campbell , John Hubbard Content-Type: text/plain; charset="UTF-8" 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 Sat, Jun 8, 2019 at 1:09 AM Jason Gunthorpe wrote: > > On Sat, Jun 08, 2019 at 01:03:48AM +0530, Souptick Joarder wrote: > > On Thu, May 23, 2019 at 9:05 PM Jason Gunthorpe wrote: > > > > > > From: Jason Gunthorpe > > > > > > So we can check locking at runtime. > > > > > > Signed-off-by: Jason Gunthorpe > > > mm/hmm.c | 4 ++-- > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > diff --git a/mm/hmm.c b/mm/hmm.c > > > index 2695925c0c5927..46872306f922bb 100644 > > > +++ b/mm/hmm.c > > > @@ -256,11 +256,11 @@ static const struct mmu_notifier_ops hmm_mmu_notifier_ops = { > > > * > > > * To start mirroring a process address space, the device driver must register > > > * an HMM mirror struct. > > > - * > > > - * THE mm->mmap_sem MUST BE HELD IN WRITE MODE ! > > > */ > > > int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm) > > > { > > > + lockdep_assert_held_exclusive(mm->mmap_sem); > > > + > > > > Gentle query, does the same required in hmm_mirror_unregister() ? > > No.. The unregistration path does its actual work in the srcu > callback, which is in a different context than this function. So any > locking held by the caller of unregister will not apply. > > The hmm_range_free SRCU callback obtains the write side of mmap_sem to > protect the same data that the write side above in register is > touching, mostly &mm->hmm. Looking into https://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma.git/tree/?h=hmm, unable trace hmm_range_free(). Am I looking into correct tree ?