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[2003:cb:c707:3700:3eea:ace6:5bde:4478]) by smtp.gmail.com with ESMTPSA id f6-20020adff586000000b003142eb75724sm5825120wro.24.2023.07.12.12.09.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 12 Jul 2023 12:09:25 -0700 (PDT) Message-ID: <7449914a-1ae3-9ea8-b60b-f0314999b790@redhat.com> Date: Wed, 12 Jul 2023 21:09:25 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH v1] mm/memory_hotplug: document the signal_pending() check in offline_pages() To: Michal Hocko Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, Oscar Salvador , Jonathan Corbet , Andrew Morton References: <20230711174050.603820-1-david@redhat.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 75AA2C000F X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: nk8wn35f6tz6okc4cqb46w5ksh41fxrb X-HE-Tag: 1689188974-198695 X-HE-Meta: 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 Y948qC40 Nqmc94dQs8WyasWCvYoTP6+/aOnaNjXLTpRcZso37zIXoo6pMm4XQk+nJmI6IigiXBzNJrcX8f7ScCrq0bNePcFxSBIWSTsHOg1lUhWPt80meL5SHREwAhDC3lETwthAnWxVi0bS5q8+8fie54wWxVTiz+ej82cCd9/+bZmWU0wU0ltUtODSSlRGpM6aW33yUhUSan1aN4C5sP/uLAQChUwjAcrzhM57cN9B7u0OetnFZTXc6ay49jK6Qxy3oVduzzQse4aq+27ay9Bw65iyokY6xrR/BB5HPj8pdUzECIl81JWFsHxdQi+r8YZQL6VbthTDQOQtJ1kUmCWA= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000014, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 11.07.23 22:47, Michal Hocko wrote: > On Tue 11-07-23 19:40:50, David Hildenbrand wrote: >> Let's update the documentation that any signal is sufficient, and >> add a comment that not only checking for fatal signals is historical >> baggage: changing it now could break existing user space. although >> unlikely. >> >> For example, when an app provides a custom SIGALRM handler and triggers >> memory offlining, the timeout cmd would no longer stop memory offlining, >> because SIGALRM would no longer be considered a fatal signal. > > Yes, and it is likely goot to mention here that this is an antipattern > for many other kernel operations like IO (e.g. write) but it is a long > term behavior that somebody might depend on and it is safer to reflect > the documentation to the realitity rather than other way around (which > would be imho better). > You mean adding something like "Note that using signal_pending() instead of fatal_signal_pending() is an anti-pattern, but slowly deprecating that behavior to eventually change it in the far future is probably not worth the effort. If this ever becomes relevant for user-space, we might want to rethink." Thanks! -- Cheers, David / dhildenb