From: Robert Love <rml@ximian.com>
To: Fabiano Ramos <ramos_fabiano@yahoo.com.br>
Cc: linux-kernel@vger.kernel.org
Subject: Re: get_task_struct()
Date: Sat, 17 Apr 2004 12:19:50 -0400 [thread overview]
Message-ID: <1082218790.10360.6.camel@localhost> (raw)
In-Reply-To: <1082216800.1447.26.camel@slack.domain.invalid>
On Sat, 2004-04-17 at 12:46 -0300, Fabiano Ramos wrote:
> Inside sys_ptrace, the function get_task_struct is invoked after
> retrieving the child's task srtuct pointer. Why is it done? I have
> tracked down the code and noticed that it is in fact an increment
> on the (page?) counter. Can you help me understand it?
Think of get_task_struct(foo) as a reference count on foo's task
structure. So long as the reference count is elevated, foo's task
structure cannot be deallocated.
get_task_struct() is called here because sys_ptrace() needs to ensure
that the child's task structure does not go away out from under this
function, but we do not want to hold the tasklist_lock.
> Is it necessary to call free_task_struct whenever its get counterpart
> is called?
Yes, although it is called "put_task_struct()". It is called at the end
of this function.
Robert Love
prev parent reply other threads:[~2004-04-17 16:19 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-04-17 15:46 get_task_struct() Fabiano Ramos
2004-04-17 16:19 ` Robert Love [this message]
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