Messages in this thread | | | Date | Tue, 4 Oct 2022 11:06:16 +0900 | From | Sergey Senozhatsky <> | Subject | Re: [PATCH printk 06/18] printk: Protect [un]register_console() with a mutex |
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On (22/10/03 21:41), John Ogness wrote: > A semaphore has been needed because we are performing global locking for > ambiguous reasons in all possible contexts. We should be using > fine-grained lock and synchronization mechanisms that are appropriate > for their used contexts to precisely lock/synchronize exactly what needs > to be locked/synchronized. > > Your first question is literally, "what is wrong with a BKL". > > And the answer to that is: A BKL is preventing us from optimizing the > kernel by decoupling unrelated activities. > > > The above proposal suggests that it might be something like: > > > > register_console() > > { > > console_list_lock(); > > > > if (!need_console()) > > goto out; > > > > if (!try_enable_console()) > > goto out; > > > > if (!(con->flags & CON_NOBLK)) > > console_lock() > > Why are you taking the console_lock here? The console_list_lock needs to > replace this responsibility. I realize the RFC and this v1 series does > not do this. For v2, it will be clear.
So tty/VT code also needs to take list_lock? list_lock does not look precisely relevant to vt, which has it's own "list" of "struct vc" to maintain.
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