Messages in this thread | | | Date | Mon, 16 Oct 2017 20:05:30 +0900 | From | Sergey Senozhatsky <> | Subject | Re: [PATCH] printk: Remove superfluous memory barriers from printk_safe |
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On (10/15/17 20:27), Steven Rostedt wrote: > > 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? > > I think this was just being overly paranoid.
hm, printk recursion is pretty easy to trigger. vscnprintf() can WARN_ON(), for instance. just pass (mistakenly) unknown printk specifier, e.g. %A, and this will do.
-ss
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