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[209.85.167.47]) by smtp.gmail.com with ESMTPSA id q20sm383205lfj.20.2019.01.30.09.18.37 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 30 Jan 2019 09:18:37 -0800 (PST) Received: by mail-lf1-f47.google.com with SMTP id c16so207756lfj.8 for ; Wed, 30 Jan 2019 09:18:37 -0800 (PST) X-Received: by 2002:a19:ef15:: with SMTP id n21mr24603026lfh.21.1548868717271; Wed, 30 Jan 2019 09:18:37 -0800 (PST) MIME-Version: 1.0 References: <201901300254.x0U2sKdE090905@www262.sakura.ne.jp> In-Reply-To: <201901300254.x0U2sKdE090905@www262.sakura.ne.jp> From: Linus Torvalds Date: Wed, 30 Jan 2019 09:18:20 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] mm: fix sleeping function warning in alloc_swap_info To: Tetsuo Handa Cc: Andrew Morton , Yang Shi , Jiufei Xue , Linux MM , joseph.qi@linux.alibaba.com 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 Tue, Jan 29, 2019 at 6:54 PM Tetsuo Handa wrote: > > Then, do we automatically defer vfree() to mm_percpu_wq context? We might do that, and say "if you call vfree with interrupts disabled, it gets deferred". That said, the deferred case should generally not be a common case either. It has real issues, one of which is simply that particularly on 32-bit architectures we can run out of vmalloc space even normally, and if there are loads that do a lot of allocation and then deferred frees, that problem could become really bad. So I'd almost be happier having a warning if we end up doing the TLB flush and defer. At least to find *what* people do. And I do wonder if we should just always warn, and have that "might_sleep()", and simply say "if you do vfree from interrupts or with interrupts disabled, you really should be aware of these kinds of issues, and you really should *show* that you are aware by using vfree_atomic()". Linus