Messages in this thread | | | Date | Sat, 14 Oct 2017 18:21:29 +0900 | From | Sergey Senozhatsky <> | Subject | Re: [PATCH] printk: Remove superfluous memory barriers from printk_safe |
| |
On (10/11/17 12:46), Steven Rostedt wrote: > From: Steven Rostedt (VMware) <rostedt@goodmis.org> > > The variable printk_safe_irq_ready is set and never cleared at system > boot up, when there's only one CPU active. It is set before other > CPUs come on line. Also, it is extremely unlikely that an NMI would > trigger this early in boot up (which I wonder why we even have this > variable at all).
it's not only NMI related, printk() recursion can happen at any stages, including... um... wait a second. ... including the "before we set up per-CPU areas" stage? hmm... smells like a bug?
do we need to move per-CPU printk_safe buffers out of per-CPU and turn it into a global static buffer? like logbuf, and just give every CPU a starting offset of its printk_safe_logbuf part.
IOW,
char printk_safe_logbuf[number of cpus * sizeof printk safe buffer];
cpu0 offset 0, up to sizeof printk safe buffer cpu1 offset sizeof printk safe buffer, up to 2 * sizeof printk safe buffer
etc.
or... at least. avoid stoing to per-CPU printk-safe/printk-nmi buffers unless we've got per-CPU areas set up? or am I hallucinating?
-ss
| |