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[195.135.220.15]) by mx.google.com with ESMTPS id g23si2416188ejm.69.2019.05.17.05.41.20 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 17 May 2019 05:41:21 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 410FBAF3A; Fri, 17 May 2019 12:41:20 +0000 (UTC) Date: Fri, 17 May 2019 14:41:19 +0200 From: Michal Hocko To: Konstantin Khlebnikov Cc: linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org, Cyrill Gorcunov , Kirill Tkhai , Al Viro Subject: Re: [PATCH 1/5] proc: use down_read_killable for /proc/pid/maps Message-ID: <20190517124119.GA1825@dhcp22.suse.cz> References: <155790967258.1319.11531787078240675602.stgit@buzz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <155790967258.1319.11531787078240675602.stgit@buzz> User-Agent: Mutt/1.10.1 (2018-07-13) 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 15-05-19 11:41:12, Konstantin Khlebnikov wrote: > Do not stuck forever if something wrong. > This function also used for /proc/pid/smaps. I do agree that the killable variant is better but I do not understand the changelog. What would keep the lock blocked for ever? I do not think we have writer lock held for unbound amount of time anywhere, do we? > Signed-off-by: Konstantin Khlebnikov Other than that Acked-by: Michal Hocko > --- > fs/proc/task_mmu.c | 6 +++++- > fs/proc/task_nommu.c | 6 +++++- > 2 files changed, 10 insertions(+), 2 deletions(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index 01d4eb0e6bd1..2bf210229daf 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -166,7 +166,11 @@ static void *m_start(struct seq_file *m, loff_t *ppos) > if (!mm || !mmget_not_zero(mm)) > return NULL; > > - down_read(&mm->mmap_sem); > + if (down_read_killable(&mm->mmap_sem)) { > + mmput(mm); > + return ERR_PTR(-EINTR); > + } > + > hold_task_mempolicy(priv); > priv->tail_vma = get_gate_vma(mm); > > diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c > index 36bf0f2e102e..7907e6419e57 100644 > --- a/fs/proc/task_nommu.c > +++ b/fs/proc/task_nommu.c > @@ -211,7 +211,11 @@ static void *m_start(struct seq_file *m, loff_t *pos) > if (!mm || !mmget_not_zero(mm)) > return NULL; > > - down_read(&mm->mmap_sem); > + if (down_read_killable(&mm->mmap_sem)) { > + mmput(mm); > + return ERR_PTR(-EINTR); > + } > + > /* start from the Nth VMA */ > for (p = rb_first(&mm->mm_rb); p; p = rb_next(p)) > if (n-- == 0) -- Michal Hocko SUSE Labs