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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20160203074223.GB30520@swordfish \
--to=sergey.senozhatsky.work@gmail.com \
--cc=akinobu.mita@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=byungchul.park@lge.com \
--cc=jack@suse.cz \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=peter@hurleysoftware.com \
--cc=torvalds@linux-foundation.org \
--cc=willy@linux.intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.