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From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Jan Kara <jack@suse.cz>,
	Andrew Morton <akpm@linux-foundation.org>,
	Tejun Heo <tj@kernel.org>, Calvin Owens <calvinowens@fb.com>,
	linux-kernel@vger.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Subject: Re: [RFC][PATCH 3/7] printk: introduce per-cpu alt_print seq buffer
Date: Fri, 30 Sep 2016 10:05:28 +0900	[thread overview]
Message-ID: <20160930010528.GB547@swordfish> (raw)
In-Reply-To: <20160929122639.GD26796@pathway.suse.cz>

On (09/29/16 14:26), Petr Mladek wrote:
[..]
> >  printk()
> >   local_irq_save()
> >   alt_printk_enter()
> 
> We need to make sure that exit() is called on the same CPU.
> Therefore we need to disable preemption as well.

local_irq_save() does this for us, we can't get sched tick or
re-sched IPI, and even more - we eliminate race conditions on
this CPU. only one path can touch alt_printk related stuff,
NMI works with its own buffer.

[..]
> What do you think about my approach with the printk_context per-CPU
> value from the WARN_DEFERRED() patchset? The main idea is that
> the entry()/exit() functions manipulate preempt_count-like per-CPU
> variable. The printk() function selects the safe implementation
> according to the current state.

I'll take a look.

hm, what I was thinking of... you are right, this all smells a bit
bad. I'll revisit it.

thanks!

	-ss

  reply	other threads:[~2016-09-30  1:05 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-27 14:22 [RFC][PATCH 0/7] printk: use alt_printk to handle printk() recursive calls Sergey Senozhatsky
2016-09-27 14:22 ` [RFC][PATCH 1/7] printk: use vprintk_func in vprintk() Sergey Senozhatsky
2016-09-27 14:22 ` [RFC][PATCH 2/7] printk: rename nmi.c and exported api Sergey Senozhatsky
2016-09-27 14:22 ` [RFC][PATCH 3/7] printk: introduce per-cpu alt_print seq buffer Sergey Senozhatsky
2016-09-29 12:26   ` Petr Mladek
2016-09-30  1:05     ` Sergey Senozhatsky [this message]
2016-09-30 11:35       ` Petr Mladek
2016-09-27 14:22 ` [RFC][PATCH 4/7] printk: make alt_printk available when config printk set Sergey Senozhatsky
2016-09-27 14:22 ` [RFC][PATCH 5/7] printk: drop vprintk_func function Sergey Senozhatsky
2016-09-27 14:22 ` [RFC][PATCH 6/7] printk: use alternative printk buffers Sergey Senozhatsky
2016-09-29 13:00   ` Petr Mladek
2016-09-30  1:15     ` Sergey Senozhatsky
2016-09-30 11:15       ` Petr Mladek
2016-10-01  2:48         ` Sergey Senozhatsky
2016-10-04 12:22           ` Petr Mladek
2016-10-05  1:36             ` Sergey Senozhatsky
2016-10-05 10:18               ` Petr Mladek
2016-10-03  7:53         ` Sergey Senozhatsky
2016-10-04 14:52         ` Petr Mladek
2016-10-05  1:27           ` Sergey Senozhatsky
2016-10-05  9:50             ` Petr Mladek
2016-10-06  4:22               ` Sergey Senozhatsky
2016-10-06 11:32                 ` Petr Mladek
2016-10-10  4:09                   ` Sergey Senozhatsky
2016-10-10 11:17                     ` Petr Mladek
2016-10-11  7:35                       ` Sergey Senozhatsky
2016-10-11  9:30                         ` Petr Mladek
2016-09-27 14:22 ` [RFC][PATCH 7/7] printk: new printk() recursion detection Sergey Senozhatsky
2016-09-29 13:19   ` Petr Mladek
2016-09-30  2:00     ` Sergey Senozhatsky
2016-09-29 13:25 ` [RFC][PATCH 0/7] printk: use alt_printk to handle printk() recursive calls Petr Mladek
2016-09-30  2:43   ` Sergey Senozhatsky
2016-09-30 11:27     ` Petr Mladek
2016-10-01  3:02       ` Sergey Senozhatsky
2016-10-04 11:35         ` Petr Mladek

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