From: Dan Malek <dan@mvista•com>
To: tom_gall@vnet•ibm.com
Cc: Tom Gall <tgall@rochcivictheatre•org>,
Troy Benjegerdes <hozer@drgw•net>,
linuxppc_commit@hq•fsmlabs.com,
linuxppc-dev <linuxppc-dev@lists•linuxppc.org>
Subject: Re: context overflow
Date: Mon, 22 Jan 2001 14:59:49 -0500 [thread overview]
Message-ID: <3A6C9135.F542F0FA@mvista.com> (raw)
In-Reply-To: 3A6C822F.7DB50A58@vnet.ibm.com
tom_gall@vnet•ibm.com wrote:
> current->mm I believe is correct. active_mm for tasks in user space just point
> back to mm. kernel space tasks will have an mm of NULL yet their active_mm will
> point back to the last user space task they ran.
Not exactly. Every task running on a CPU must have an active_mm, and
it represents the current context for the MMU. This active_mm comes
from a single threaded application's 'mm', or in the case of a
thread without an 'mm' from the previous application that ran, or
from somewhere else depending upon VM_CLONE games.
The point you are missing is 'active_mm' represents the current
context for the MMU. If you get a context overflow, you can't skip
getting and setting a context for an active task just because it
doesn't have a 'current->mm'. Your modification to do this
results in a task running on a CPU with a "NO CONTEXT" mm, and worse
and incorrect VSID/ASID/PID/whatever for the task running on that MMU.
> The reason for this patch is in the case where the idle task comes in on one
> processor and on another processor it has encountered a context overflow.
It's not just the idle task. It could be any task that is supposed
to get an active_mm from someone else.
The patch is just logically incorrect. There should be no
'if current->mm' and it should get/set context on current->active_mm.
-- Dan
** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/
next prev parent reply other threads:[~2001-01-22 19:59 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-01-20 2:27 context overflow Dan Malek
2001-01-22 4:28 ` Troy Benjegerdes
2001-01-22 4:39 ` Tom Gall
2001-01-22 18:10 ` Dan Malek
2001-01-22 18:55 ` tom_gall
2001-01-22 19:59 ` Dan Malek [this message]
2001-01-22 22:08 ` tom_gall
2001-01-23 0:10 ` Dan Malek
2001-01-23 10:00 ` Gabriel Paubert
2001-01-23 18:21 ` Dan Malek
2001-02-06 10:55 ` Paul Mackerras
2001-02-06 21:11 ` Dan Malek
2001-02-06 21:50 ` Paul Mackerras
2001-02-06 22:29 ` Dan Malek
2001-02-06 22:45 ` Paul Mackerras
2001-02-06 10:50 ` Paul Mackerras
2001-02-06 21:32 ` Dan Malek
2001-02-06 22:08 ` Paul Mackerras
2001-02-06 23:14 ` Dan Malek
2001-02-07 0:23 ` Paul Mackerras
2001-02-07 18:02 ` Dan Malek
2001-02-08 0:48 ` Paul Mackerras
2001-02-08 1:39 ` Frank Rowand
2001-02-08 19:00 ` David Edelsohn
2001-02-08 20:53 ` Roman Zippel
2001-02-08 21:14 ` David Edelsohn
2001-02-08 23:23 ` Roman Zippel
2001-02-08 23:48 ` Cort Dougan
2001-02-08 21:28 ` Cort Dougan
2001-02-08 22:08 ` David Edelsohn
2001-02-08 22:26 ` Cort Dougan
2001-02-08 23:17 ` David Edelsohn
2001-02-08 23:27 ` Cort Dougan
2001-02-08 23:28 ` Gabriel Paubert
2001-02-09 9:58 ` Paul Mackerras
2001-02-09 10:57 ` Gabriel Paubert
2001-02-09 11:26 ` Paul Mackerras
2001-02-09 10:49 ` Paul Mackerras
2001-02-07 9:18 ` Roman Zippel
2001-02-07 17:46 ` Dan Malek
2001-02-07 18:39 ` Roman Zippel
2001-02-07 21:16 ` Gabriel Paubert
2001-02-08 0:34 ` Paul Mackerras
2001-01-22 4:55 ` Larry McVoy
2001-01-22 6:15 ` Troy Benjegerdes
2001-01-23 1:12 ` Frank Rowand
2001-01-23 1:20 ` Dan Malek
2001-01-23 2:12 ` Frank Rowand
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