On (10/03/18 11:23), Petr Mladek wrote:
> On Fri 2018-09-28 18:53:04, Sergey Senozhatsky wrote:
> > CON_PRINTBUFFER console registration requires us to do several
> > preparation steps:
> > - Rollback console_seq to replay logbuf messages which were already
> > seen on other consoles;
> > - Set exclusive_console flag so console_unlock() will ->write() logbuf
> > messages only to the exclusive_console driver.
> >
> > The way we do it, however, is a bit racy
> >
> > logbuf_lock_irqsave(flags);
> > console_seq = syslog_seq;
> > console_idx = syslog_idx;
> > logbuf_unlock_irqrestore(flags);
> > << preemption enabled
> > << irqs enabled
> > exclusive_console = newcon;
> > console_unlock();
> >
> > We rollback console_seq under logbuf_lock with IRQs disabled, but
> > we set exclusive_console with local IRQs enabled and logbuf unlocked.
> > If the system oops-es or panic-s before we set exclusive_console - and
> > given that we have IRQs and preemption enabled there is such a
> > possibility - we will re-play all logbuf messages to every registered
> > console, which may be a bit annoying and time consuming.
> >
> > Move exclusive_console assignment to the same IRQs-disabled and
> > logbuf_lock-protected section where we rollback console_seq.
> >
> > Signed-off-by: Sergey Senozhatsky <sergey.senozhat...@gmail.com>
>
> JFYI, I have just pushed this into printk.git, for-4.20 branch.
Thanks.
-ss
