Messages in this thread | | | Date | Fri, 30 Sep 2016 10:05:28 +0900 | From | Sergey Senozhatsky <> | Subject | Re: [RFC][PATCH 3/7] printk: introduce per-cpu alt_print seq buffer |
| |
On (09/29/16 14:26), Petr Mladek wrote: [..] > > printk() > > local_irq_save() > > alt_printk_enter() > > We need to make sure that exit() is called on the same CPU. > Therefore we need to disable preemption as well.
local_irq_save() does this for us, we can't get sched tick or re-sched IPI, and even more - we eliminate race conditions on this CPU. only one path can touch alt_printk related stuff, NMI works with its own buffer.
[..] > What do you think about my approach with the printk_context per-CPU > value from the WARN_DEFERRED() patchset? The main idea is that > the entry()/exit() functions manipulate preempt_count-like per-CPU > variable. The printk() function selects the safe implementation > according to the current state.
I'll take a look.
hm, what I was thinking of... you are right, this all smells a bit bad. I'll revisit it.
thanks!
-ss
| |