From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: Byungchul Park <byungchul.park@lge.com>,
willy@linux.intel.com, akpm@linux-foundation.org,
linux-kernel@vger.kernel.org, akinobu.mita@gmail.com,
jack@suse.cz, sergey.senozhatsky.work@gmail.com,
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 16:42:23 +0900 [thread overview]
Message-ID: <20160203074223.GB30520@swordfish> (raw)
In-Reply-To: <20160203072847.GA32026@gmail.com>
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.
-ss
next prev parent reply other threads:[~2016-02-03 7:41 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 [this message]
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
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