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Thu, 30 Mar 2023 01:20:05 -0700 (PDT) MIME-Version: 1.0 References: <20230328221644.803272-1-yosryahmed@google.com> <20230328221644.803272-5-yosryahmed@google.com> <20230329192059.2nlme5ubshzdbpg6@google.com> In-Reply-To: From: Yosry Ahmed Date: Thu, 30 Mar 2023 01:19:29 -0700 Message-ID: Subject: Re: [PATCH v2 4/9] cgroup: rstat: add WARN_ON_ONCE() if flushing outside task context To: Michal Hocko Cc: Johannes Weiner , Shakeel Butt , Tejun Heo , Josef Bacik , Jens Axboe , Zefan Li , Roman Gushchin , Muchun Song , Andrew Morton , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Vasily Averin , cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: fjat6gj7ky9i486y4fgo9ycba98guhnz X-Rspamd-Queue-Id: 5A96A100006 X-HE-Tag: 1680164407-281238 X-HE-Meta: U2FsdGVkX193eTqtuaB395KA/HICrJ4n+uKJCARL5GdeHHTWQ+/cVn1CNBIdCXB3bmyX/aeXFrY4K0GmP24oJhQgfpmTMkXBxZ7+lrd7VAp2U7UEkQ80yohtGO4I1zmEVj+XIRtAmy9YTtG7q+FEsk42hupQPwyQ5yYWcKVHU8zlBLKcFI5BgRHuFFjAfbAh8lC74VgyQ4ps8MRI5VDmLZqOPkTv3mgg35ktupDZLWG8XzjHGmDH1k8nsgRoul7V67zZf861BfoxYxzT4WUdEengra5b0641AxArkVvZ764njBJZUm27ZVSdwfGjYiGP6wN9vwd5GGmQPHohS6qEAZaWpMYLjN5NT7ykg1xYCVltTbfLaXPFCp3xpZUy935R2M1H6HWSBmfoX0Rzhu6/CoI4lvYG6/6Agwx1SHckrJtT7l66kJrD6BJny1rdGe5GHgVFdG9KDY6j9aw2uq9GGAHBEOhHifaKwLqLfEhEQZ0gGXR1MiddfG11G6s0VyFw7hOhMD13p43kNj2W3CmTpVPNIZ1owUjVbbzTa5qwVzlIDImQpd4ZzTT2GEekX0xsFWgq+1HleiUFoo3IiIsmisfNskhmS/qAxUNPMhqhznQ6CfGm8ipqOenldHWdPbDn4UucZPHLYHqaY7p5tqXavatVsokvp5IKHdJ5qKdlK9O3IuvQ9v7z9d0RL3D1Pep3zt125zlxJpzULcSAdkpxY0VyZ+3CQJ283UddHY8vCF2vV9LcFZqG4vTl2MOHZAF6/J965Ih0dIe4i/MKE95WurhcIZGIDy1ZzbQ0q75wp+bqsecZLhDEy7uFzEHbHn5JBTarnvWmIK4t12094i8Xw1QvxVGDMApJEXY7YhWxx86B/Srd6SFwKNNJcpma+V0PV5hmL7wYxuZ7FKQZMOEX/UCrFUg/X6Dr7MWQ5SGf3CwXS0s99GWURo0D3CjPHYwFyZGLBjG+bPcqMnlXT1T NQ8/0ur+ OYnNs9Rhn+tmaibjeWBIGnPsCcsbGGpPg0ayEPINfAsLrQaHQUPHOdoD4CclaOQGZqKzRBhfcZORvWhd5+FxBSSyQYJAKiBP9KIin9qaTWDoNJBGzprRD8k1+QGgf3ieesRes1mqQOs5mdXj90tNuvwhLYlMdgn27mHYysY14vYiZuqHuJRX8ohwYXPAgFmFydLgH0t/YxXsrbb+SiI7iWW3/1z2Qj196XsR2+O2IoEDuENJyWg8nPdoFk74hME7sZS/r/O2Pp1GQmfZVXinU2i6C0pGf/rWZ/p5j7t9gvPIPto4yPnbazevZljVOX92GLXbXb3cyNeVIzxSSbNH/7gDQeGY9Qn/2omoe 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, Mar 30, 2023 at 1:15=E2=80=AFAM Michal Hocko wrot= e: > > On Thu 30-03-23 01:06:26, Yosry Ahmed wrote: > [...] > > If we achieve that, do you think it makes sense to add > > WARN_ON_ONCE(irqs_disabled()) instead to prevent future users from > > flushing while disabling irqs or in irq context? > > WARN_ON (similar to BUG_ON) will not prevent anybody from doing bad > things. We already have means to shout about sleepable code being > invoked from an atomic context and there is no reason to duplicate that. > As I've said earlier WARN_ON might panic the system in some > configurations (and yes they are used also in production systems - do > not ask me why...). So please be careful about that and use that only > when something really bad (yet recoverable) is going on. Thanks for the information (I was about to ask why about production systems, but okay..). I will avoid WARN_ON completely. For the purposes of this series I will drop this patch anyway. Any idea how to shout about "hey this may take too long, why are you doing it with irqs disabled?!"? > > -- > Michal Hocko > SUSE Labs