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Wed, 04 Dec 2024 19:23:54 -0800 (PST) Received: from google.com ([2401:fa00:8f:203:84f:5a2a:8b5d:f44f]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-215f8e5f30fsm2758825ad.74.2024.12.04.19.23.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Dec 2024 19:23:53 -0800 (PST) Date: Thu, 5 Dec 2024 12:23:49 +0900 From: Sergey Senozhatsky To: Brian Geffon Cc: Tomasz Figa , Joanne Koong , Bernd Schubert , Sergey Senozhatsky , Bernd Schubert , "miklos@szeredi.hu" , "linux-fsdevel@vger.kernel.org" , "josef@toxicpanda.com" , "jefflexu@linux.alibaba.com" , "laoar.shao@gmail.com" , "kernel-team@meta.com" Subject: Re: [PATCH RESEND v9 2/3] fuse: add optional kernel-enforced timeout for requests Message-ID: <20241205032349.GC16709@google.com> References: <20241128104437.GB10431@google.com> <25e0e716-a4e8-4f72-ad52-29c5d15e1d61@fastmail.fm> <20241128110942.GD10431@google.com> <8c5d292f-b343-435f-862e-a98910b6a150@ddn.com> <20241128115455.GG10431@google.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On (24/12/04 09:51), Brian Geffon wrote: > > > > >> > > > > >> In those cases 1 minute fuse timeout will overshot HUNG_TASK_TIMEOUT > > > > >> and then the question is whether HUNG_TASK_PANIC is set. > > In my opinion this is a good argument for having the hung task timeout > and a fuse timeout independent. The hung task timeout is for hung > kernel threads Sorry, but no, it's not only for kernel threads. > in this situation we're potentially taking too long in > userspace but that doesn't necessarily mean the system is hung. And it's not for hung system. It's for tasks that stuck unreasonably long waiting for a particular event or resource. And those tasks very well can be user-space processes, being stuck in syscall waiting for something. > I think a loop which does an interruptible wait with a timeout of 1/2 > the hung task timeout would make sense to ensure the hung task timeout > doesn't hit. The point here is not to silent watchdog, we might as well just disable it and call it a day. The point here is that fuse can be used (and IS in our particular case) as a network filesystem, and the problem can be way outside of your system, so spinning in a wait loop doesn't fix any problem on that remote system no matter how long we spin, and that's what watchdog signals us.