Messages in this thread | | | From | Eric Dumazet <> | Date | Wed, 6 Jul 2022 09:00:11 +0200 | Subject | Re: [PATCH v1 net 03/16] sysctl: Add proc_dointvec_lockless(). |
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On Wed, Jul 6, 2022 at 7:22 AM Kuniyuki Iwashima <kuniyu@amazon.com> wrote: > > A sysctl variable is accessed concurrently, and there is always a chance of > data-race. So, all readers and writers need some basic protection to avoid > load/store-tearing. > > This patch changes proc_dointvec() to use READ_ONCE()/WRITE_ONCE() > internally to fix a data-race on the sysctl side. For now, proc_dointvec() > itself is tolerant to a data-race, but we still need to add annotations on > the other subsystem's side. > > In case we miss such fixes, this patch converts proc_dointvec() to a > wrapper of proc_dointvec_lockless(). When we fix a data-race in the other > subsystem, we can explicitly set it as a handler. > > Also, this patch removes proc_dointvec()'s document and adds > proc_dointvec_lockless()'s one so that no one will use proc_dointvec() > anymore. > > While we are on it, we remove some trailing spaces.
I do not see why you add more functions.
Really all sysctls can change locklessly by nature, as I pointed out.
So I would simply add WRITE_ONCE() whenever they are written, and READ_ONCE() when they are read.
If stable teams care enough, they will have to backport these changes, so I would rather not have to change proc_dointvec() to proc_dointvec_lockless() in many files, with many conflicts, that ultimately will either add bugs, or ask extra work for maintainers.
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