Messages in this thread | | | Date | Thu, 11 Jun 2015 11:57:05 +0200 | From | Petr Mladek <> | Subject | Re: [RFC][PATCH] printk: Fixup the nmi printk mess |
| |
On Wed 2015-06-10 17:29:17, Peter Zijlstra wrote: > On Wed, Jun 10, 2015 at 04:31:55PM +0200, Petr Mladek wrote: > > If another NMI comes at this point, it will start filling the buffer > > from the beginning. If it is fast enough, it might override the text > > that we print above. > > How so? If the cmpxchg succeeded and len == 0, we flushed everything and > are done with it, if another NMI comes in and 'overwrites' it, that's > fine, right?
Shame on me. Somehow I thought that there was xchg() and not cmpxchg().
> > > +static int vprintk_nmi(const char *fmt, va_list args) > > > +{ > > > + struct nmi_seq_buf *s = this_cpu_ptr(&nmi_print_seq); > > > + unsigned int len = seq_buf_used(&s->seq); > > > + > > > + irq_work_queue(&s->work); > > > + seq_buf_vprintf(&s->seq, fmt, args); > > No, everything is strictly per cpu.
I do not know why but I expected that irq_work could get proceed on any CPU. You are right. They are proceed on the same one.
Similar with the other mail. Sigh, I was too fast yesterday. I am sorry for the noise.
Best Regards, Petr
| |