Messages in this thread | | | Date | Tue, 29 Nov 2016 15:10:55 +0100 | From | Petr Mladek <> | Subject | Re: [PATCH 3/3] early_printk: Add simple serialization to early_vprintk() |
| |
On Tue 2016-10-18 19:08:33, Peter Zijlstra wrote: > In order to avoid multiple CPUs banging on the serial port at the same > time, add simple serialization. This explicitly deals with nested > contexts (like IRQs etc.). > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Makes sense. Just a small comment below.
Reviewd-by: Petr Mladek <pmladek@suse.com>
> --- a/kernel/printk/printk.c > +++ b/kernel/printk/printk.c > @@ -356,14 +356,28 @@ static int __init force_early_printk_set > } > early_param("force_early_printk", force_early_printk_setup); > > +static int early_printk_cpu = -1;
[...]
> + for (;;) { > + old = cmpxchg(&early_printk_cpu, -1, cpu); > + if (old == -1 || old == cpu) > + break; > + > + cpu_relax(); > + } > > n = vscnprintf(buf, sizeof(buf), fmt, args); > early_console->write(early_console, buf, n); > > + smp_store_release(&early_printk_cpu, old);
checkpatch.pl complains about using a barrier without a comment. The code is simple but it still might help to add something like:
/* Releasing early_printk_cpu custom lock. */
Best Regards, Petr
| |