From: David Rientjes <rientjes@google.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>, John Stultz <john.stultz@linaro.org>,
LKML <linux-kernel@vger.kernel.org>,
Joe Perches <joe@perches.com>,
Michal Nazarewicz <mina86@mina86.com>,
Andy Whitcroft <apw@canonical.com>,
Jiri Slaby <jirislaby@gmail.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Dave Hansen <dave@linux.vnet.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org
Subject: Re: [PATCH 1/3] comm: Introduce comm_lock spinlock to protect task->comm access
Date: Tue, 17 May 2011 15:56:24 -0700 (PDT) [thread overview]
Message-ID: <alpine.DEB.2.00.1105171551450.10386@chino.kir.corp.google.com> (raw)
In-Reply-To: <1305669256.2466.6286.camel@twins>
On Tue, 17 May 2011, Peter Zijlstra wrote:
> The changelog also fails to mention _WHY_ this is no longer true. Nor
> does it treat why making it true again isn't an option.
>
It's been true since:
4614a696bd1c3a9af3a08f0e5874830a85b889d4
Author: john stultz <johnstul@us.ibm.com>
Date: Mon Dec 14 18:00:05 2009 -0800
procfs: allow threads to rename siblings via /proc/pid/tasks/tid/comm
Although at the time it appears that nobody was concerned about races so
proper syncronization was never implemented. We always had the
prctl(PR_SET_NAME) so the majority of comm reads, those to current,
required no locking, but this commit changed that. The remainder of comm
dereferences always required task_lock() and the helper get_task_comm() to
read the string into a (usually stack-allocated) buffer.
> Who is changing another task's comm? That's just silly.
>
I agree, and I suggested taking write privileges away from /proc/pid/comm,
but others find that it is useful to be able to differentiate between
threads in the same thread group without using the prctl() for debugging?
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next prev parent reply other threads:[~2011-05-17 22:56 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-17 20:47 [PATCH 0/3] v5 Improve task->comm locking situation John Stultz
2011-05-17 20:47 ` [PATCH 1/3] comm: Introduce comm_lock spinlock to protect task->comm access John Stultz
2011-05-17 21:27 ` Ingo Molnar
2011-05-17 21:54 ` Peter Zijlstra
2011-05-17 22:56 ` David Rientjes [this message]
2011-05-18 0:53 ` KOSAKI Motohiro
2011-05-17 22:27 ` John Stultz
2011-05-18 1:02 ` KOSAKI Motohiro
2011-05-17 20:47 ` [PATCH 2/3] printk: Add %ptc to safely print a task's comm John Stultz
2011-05-17 21:42 ` Jiri Slaby
2011-05-17 21:52 ` Joe Perches
2011-05-17 22:04 ` Jiri Slaby
2011-05-17 22:17 ` Joe Perches
2011-05-17 22:17 ` John Stultz
2011-05-17 20:47 ` [PATCH 3/3] checkpatch.pl: Add check for task comm references John Stultz
2011-05-17 20:58 ` Jiri Slaby
2011-05-17 21:04 ` Michal Nazarewicz
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