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From: ebiederm@xmission.com (Eric W. Biederman)
To: Andrew Morton <akpm@osdl.org>
Cc: <linux-kernel@vger.kernel.org>, Oleg Nesterov <oleg@tv-sign.ru>
Subject: Re: [PATCH 01/23] tref: Implement task references.
Date: Thu, 23 Feb 2006 09:49:07 -0700	[thread overview]
Message-ID: <m1mzgidnr0.fsf@ebiederm.dsl.xmission.com> (raw)
In-Reply-To: <m1k6bmhxze.fsf@ebiederm.dsl.xmission.com> (Eric W. Biederman's message of "Thu, 23 Feb 2006 08:54:29 -0700")

ebiederm@xmission.com (Eric W. Biederman) writes:

> Holding a reference to a task_struct pins about 10K of low memory even
> after that task has exited.  Which seems to be at 1 or 2 orders of
> mangnitude more memory than any other data structure in the kernel.
> Not holding a reference to a task_struct and you risk problems with
> pid wrap around.
>
> Even worse because we allow session and process group leaders to exit
> there is no task_struct you can hold onto to prevent pid wrap around
> problems for those kinds of structures.
>
> The task_ref is an small intermediate data structure that other
> structures can point, that solves these problems.  A task_ref will
> always point at the first user of a pid value or contain a NULL
> pointer if there are no longer any users of that pid.

I forgot to note that there is a correctness dependence on an my
kill switch_exec_pids patch.  Without that task_refs will
stop being able to track a pid when we pass it on to
a new process in de_thread.

I built this patchset against Linus latest kernel and not -mm so I think
I may have one or two trivial conflicts with Olegs changes as
well.  In particular I have some changes to unhash_process() that Oleg
has removed, but simply removing that hunch should be all the resolution
that is needed.  Hopefully that won't be a problem..

Eric

  parent reply	other threads:[~2006-02-23 16:50 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-02-23 15:52 [PATCH 00/23] proc cleanup Eric W. Biederman
2006-02-23 15:54 ` [PATCH 01/23] tref: Implement task references Eric W. Biederman
2006-02-23 15:56   ` [PATCH 02/23] proc: Fix the .. inode number on /proc/<pid>/fd Eric W. Biederman
2006-02-23 15:57     ` [PATCH 03/23] proc: Remove useless BKL in proc_pid_readlink Eric W. Biederman
2006-02-23 15:58       ` [PATCH 04/23] proc: Remove unnecessary and misleading assignments from proc_pid_make_inode Eric W. Biederman
2006-02-23 16:00         ` [PATCH 05/23] proc: Simplify the ownership rules for /proc Eric W. Biederman
2006-02-23 16:02           ` Eric W. Biederman
2006-02-23 16:04           ` [PATCH 06/23] proc: Replace proc_inode.type with proc_inode.fd Eric W. Biederman
2006-02-23 16:05             ` [PATCH 07/23] proc: Remove bogus proc_task_permission Eric W. Biederman
2006-02-23 16:06               ` [PATCH 08/23] proc: Kill proc_mem_inode_operations Eric W. Biederman
2006-02-23 16:08                 ` [PATCH 09/23] proc: Properly filter out files that are not visible to a process Eric W. Biederman
2006-02-23 16:10                   ` [PATCH 10/23] proc: Fix the link count for /proc/<pid>/task Eric W. Biederman
2006-02-23 16:12                     ` [PATCH 11/23] proc: Move proc_maps_operations into task_mmu.c Eric W. Biederman
2006-02-23 16:15                       ` [PATCH 12/23] proc: Rewrite the proc dentry flush on exit optimization Eric W. Biederman
2006-02-23 16:16                         ` [PATCH 13/23] proc: Close the race of a process dying durning lookup Eric W. Biederman
2006-02-23 16:18                           ` [PATCH 14/23] proc: Make PROC_NUMBUF the buffer size for holding a integers as strings Eric W. Biederman
2006-02-23 16:20                             ` [PATCH 15/23] proc: refactor reading directories of tasks Eric W. Biederman
2006-02-23 16:23                               ` [PATCH 16/23] proc: Don't lock task_structs indefinitely Eric W. Biederman
2006-02-23 16:24                                 ` [PATCH 17/23] proc: Give the root directory a task Eric W. Biederman
2006-02-23 16:25                                   ` [PATCH 18/23] proc: Reorder the functions in base.c Eric W. Biederman
2006-02-23 16:27                                     ` [PATCH 19/23] proc: Modify proc_pident_lookup to be completely table driven Eric W. Biederman
2006-02-23 16:28                                       ` [PATCH 20/23] proc: Make the generation of the self symlink " Eric W. Biederman
2006-02-23 16:30                                         ` [PATCH 21/23] proc: Factor out an instantiate method from every lookup method Eric W. Biederman
2006-02-23 16:32                                           ` [PATCH 22/23] proc: Remove the hard coded inode numbers Eric W. Biederman
2006-02-23 16:34                                             ` [PATCH 23/23] proc: Merge proc_tid_attr and proc_tgid_attr Eric W. Biederman
2006-02-23 16:49   ` Eric W. Biederman [this message]
2006-03-02 19:16     ` [PATCH 01/23] tref: Implement task references Oleg Nesterov
2006-03-02 20:37       ` Oleg Nesterov
2006-03-02 22:19       ` Eric W. Biederman
2006-03-03 16:56         ` Oleg Nesterov
2006-03-03 17:48           ` Eric W. Biederman
2006-03-04 11:16           ` Eric W. Biederman
2006-03-04 12:31             ` Oleg Nesterov
2006-03-04 17:30               ` Oleg Nesterov
2006-03-06 21:06         ` Oleg Nesterov
2006-03-06 22:18           ` Eric W. Biederman
2006-03-07 20:44             ` Oleg Nesterov
2006-03-07  1:39           ` Eric W. Biederman
2006-03-07 20:38             ` Oleg Nesterov
2006-03-07 13:12           ` Eric W. Biederman
2006-03-07 21:02             ` Oleg Nesterov
2006-03-07 23:00               ` Eric W. Biederman
2006-03-03 19:23     ` Oleg Nesterov
2006-03-04 10:51       ` Eric W. Biederman
2006-02-25 12:27 ` [PATCH 00/23] proc cleanup Andrew Morton
2006-02-25 13:34   ` Eric W. Biederman
2006-02-25 15:20   ` Eric W. Biederman
2006-02-27 15:26 ` Serge E. Hallyn
2006-02-27 15:56   ` Eric W. Biederman

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