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
next prev parent 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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