On Thu 10-10-19 14:12:01, Sergey Senozhatsky wrote: > On (10/09/19 16:26), Michal Hocko wrote: > > On Wed 09-10-19 15:56:32, Peter Oberparleiter wrote: > > [...] > > > A generic solution would be preferable from my point of view though, > > > because otherwise each console driver owner would need to ensure that any > > > lock taken in their console.write implementation is never held while > > > memory is allocated/released. > > > > Considering that console.write is called from essentially arbitrary code > > path IIUC then all the locks used in this path should be pretty much > > tail locks or console internal ones without external dependencies. > > That's a good expectation, but I guess it's not always the case. > > One example might be NET console - net subsystem locks, net device > drivers locks, maybe even some MM locks (skb allocations?). I am not familiar with the netconsole code TBH. If there is absolutely no way around that then we might have to bite a bullet and consider some of MM locks a land of no printk. I have already said that in this thread. I am mostly pushing back on "let's just go the simplest way" approach. > But even more "commonly used" consoles sometimes break that > expectation. E.g. 8250 > > serial8250_console_write() > serial8250_modem_status() > wake_up_interruptible() By that expectation you mean they are using external locks or that they really _need_ to allocate. Because if you are pointing to wake_up_interruptible and therefore the rq then this is a well known thing and I was under impression even documented but I can only see LOGLEVEL_SCHED that is arguably a very obscure way to document the fact. -- Michal Hocko SUSE Labs
