linux-kernel - Re: [PATCH 2/2] printk: make sure to print log on console.

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Message-ID: <20180531122112.bfeqtmwpl2qc67a5@pathway.suse.cz>
Date:   Thu, 31 May 2018 14:21:12 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     Maninder Singh <maninder1.s@...sung.com>,
        sergey.senozhatsky@...il.com, rostedt@...dmis.org,
        linux-kernel@...r.kernel.org, a.sahrawat@...sung.com,
        pankaj.m@...sung.com, v.narang@...sung.com
Subject: Re: [PATCH 2/2] printk: make sure to print log on console.

On Thu 2018-05-31 19:52:15, Sergey Senozhatsky wrote:
> On (05/31/18 15:49), Maninder Singh wrote:
> > 
> > This patch make sure printing of log if loglevel at time of storing
> > log is greater than current console loglevel.
> > 
> > @why
> > In case of async printk, printk thread can miss logs because it checks
> > current log level at time of console_unlock.
> 
> Upstream printk has no printing kthread. And we also run
> printk()->console_unlock() with disabled preemption.

Yes, the comment was wrong but the problem is real. The console
handling is asynchronous even without the kthread. The current
console_lock owner is responsible for handling messages also
from other CPUs.

Best Regards,
Petr