From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Byungchul Park <byungchul.park@lge.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Ingo Molnar <mingo@kernel.org>,
willy@linux.intel.com, akpm@linux-foundation.org,
linux-kernel@vger.kernel.org, akinobu.mita@gmail.com,
jack@suse.cz, peter@hurleysoftware.com,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH v2] lock/semaphore: Avoid an unnecessary deadlock within up()
Date: Wed, 3 Feb 2016 17:30:30 +0900 [thread overview]
Message-ID: <20160203083030.GD30520@swordfish> (raw)
In-Reply-To: <20160203081242.GA32743@X58A-UD3R>
On (02/03/16 17:12), Byungchul Park wrote:
> On Wed, Feb 03, 2016 at 04:42:23PM +0900, Sergey Senozhatsky wrote:
> > On (02/03/16 08:28), Ingo Molnar wrote:
> > [..]
> > > So why not move printk away from semaphores? Semaphores are classical constructs
> > > that have legacies and are somewhat non-obvious to use, compared to modern,
> > > simpler locking primitives. I'd not touch their implementation, unless we are
> > > absolutely sure this is a safe optimization.
> >
> > semaphore's spin_lock is not the only spin lock that printk acquires. it also takes the
> > logbuf_lock (and different locks in console drivers (up to console driver)).
> >
> > Jan Kara posted a patch that offloads printing job (console_trylock()-console_unlock())
> > from printk() call (when printk can offload it). so semaphore and console driver's locks
> > will go away (mostly) with Jan's patch. logbug spin_lock, however, will stay.
>
> It sounds good. Could you teach me how to see the patch by Jan?
sure,
https://lkml.org/lkml/2015/10/26/16
and
http://marc.info/?l=linux-kernel&m=145079206822115
-ss
prev parent reply other threads:[~2016-02-03 8:29 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-03 6:02 [PATCH v2] lock/semaphore: Avoid an unnecessary deadlock within up() Byungchul Park
2016-02-03 7:28 ` Ingo Molnar
2016-02-03 7:42 ` Sergey Senozhatsky
2016-02-03 8:04 ` Ingo Molnar
2016-02-03 8:28 ` Sergey Senozhatsky
2016-02-03 9:02 ` Ingo Molnar
2016-02-03 8:12 ` Byungchul Park
2016-02-03 8:30 ` Sergey Senozhatsky [this message]
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