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From: Mathieu Poirier <mathieu.poirier@linaro.org>
To: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: tsoni@codeaurora.org, saiprakash.ranjan@codeaurora.org,
	kim.phillips@arm.com, jinlmao@codeaurora.org,
	alexander.shishkin@linux.intel.com, gregkh@linuxfoundation.org,
	coresight@lists.linaro.org, rdunlap@infradead.org,
	ykaukab@suse.de, linux@armlinux.org.uk, tingwei@codeaurora.org,
	leo.yan@linaro.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 19/20] coresight: add try_get_module() in coresight_grab_device()
Date: Thu, 23 Jul 2020 13:36:01 -0600	[thread overview]
Message-ID: <20200723193601.GC1323936@xps15> (raw)
In-Reply-To: <7ef8d427-23c9-10cd-b337-03ae75476a8c@arm.com>

Hi Suzuki,

On Wed, Jul 22, 2020 at 11:49:48AM +0100, Suzuki K Poulose wrote:
> Hi Tingwei,
> 
> On 07/17/2020 06:45 AM, Tingwei Zhang wrote:
> > When coresight device is in an active session, driver module of
> > that device should not be removed. Use try_get_module() in
> > coresight_grab_device() to prevent module to be unloaded.
> > 
> 
> Is this really sufficient ? AFAIU, a device could be removed, but the
> module may still be alive due to the refcount on the module. This

If I understand correctly you are worried about cases where drivers would be
removed but not the reference of the devices using those drivers in the
coresight port connections?  If so you are very right.  Otherwise please expand
on the scenario you have in mind.

The first version of this set was doing all that cleanup...  I haven't looked at
this set yet but from what I've seen the cleanup code is not present in any
of the sets after V1.  Tingwei, is the work done in coresight_disable_match()
part of the later revisions?

> could imply that we have stale pointers in the _path_, which could
> lead to corruption elsewhere. Should we do a get/put_device() instead ?
> 
> Cheers
> Suzuki

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  parent reply	other threads:[~2020-07-23 19:37 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-17  5:45 [PATCH v3 00/20] coresight: allow to build coresight as modules Tingwei Zhang
2020-07-17  5:45 ` [PATCH v3 01/20] coresight: cpu_debug: add module name in Kconfig Tingwei Zhang
2020-07-17  5:45 ` [PATCH v3 02/20] coresight: cpu_debug: define MODULE_DEVICE_TABLE Tingwei Zhang
2020-07-17  5:45 ` [PATCH v3 03/20] coresight: use IS_ENABLED for CONFIGs that may be modules Tingwei Zhang
2020-07-17  5:45 ` [PATCH v3 04/20] coresight: add coresight prefix to barrier_pkt Tingwei Zhang
2020-07-17  5:45 ` [PATCH v3 05/20] coresight: export global symbols Tingwei Zhang
2020-07-17  5:45 ` [PATCH v3 06/20] Allow to build coresight-stm as a module, for ease of development Tingwei Zhang
2020-07-17  5:45 ` [PATCH v3 07/20] coresight: allow etm3x to be built as a module Tingwei Zhang
2020-07-17  5:45 ` [PATCH v3 08/20] coresight: allow etm4x " Tingwei Zhang
2020-07-17 17:05   ` Mike Leach
2020-07-18  3:25     ` tingwei
2020-07-18 17:38       ` Mike Leach
2020-07-21 14:55         ` Mathieu Poirier
2020-07-21 23:22           ` tingwei
2020-07-20  6:58   ` Sai Prakash Ranjan
2020-07-21  7:03     ` Sai Prakash Ranjan
2020-07-17  5:45 ` [PATCH v3 09/20] coresight: allow etb " Tingwei Zhang
2020-07-17  5:45 ` [PATCH v3 10/20] coresight: allow tpiu " Tingwei Zhang
2020-07-17  5:45 ` [PATCH v3 11/20] coresight: allow tmc " Tingwei Zhang
2020-07-17  5:45 ` [PATCH v3 12/20] coresight: remove multiple init calls from funnel driver Tingwei Zhang
2020-07-17  5:45 ` [PATCH v3 13/20] coresight: remove multiple init calls from replicator driver Tingwei Zhang
2020-07-17  5:45 ` [PATCH v3 14/20] coresight: allow funnel and replicator drivers to be built as modules Tingwei Zhang
2020-07-17  5:45 ` [PATCH v3 15/20] coresight: cti: add function to register cti associate ops Tingwei Zhang
2020-07-17  5:45 ` [PATCH v3 16/20] coresight: allow cti to be built as a module Tingwei Zhang
2020-07-20 17:00   ` Mike Leach
2020-07-20 21:07     ` Mike Leach
2020-07-21 16:35       ` Mike Leach
2020-07-21 23:27         ` tingwei
2020-07-17  5:45 ` [PATCH v3 17/20] coresight: tmc-etr: add function to register catu ops Tingwei Zhang
2020-07-17  5:45 ` [PATCH v3 18/20] coresight: allow catu drivers to be built as modules Tingwei Zhang
2020-07-17  5:45 ` [PATCH v3 19/20] coresight: add try_get_module() in coresight_grab_device() Tingwei Zhang
2020-07-22 10:49   ` Suzuki K Poulose
2020-07-22 10:48     ` Greg KH
2020-07-22 11:26       ` Suzuki K Poulose
2020-07-23  0:18         ` tingwei
2020-07-23  0:35       ` tingwei
2020-07-22 10:51     ` Suzuki K Poulose
2020-07-23  0:19       ` tingwei
2020-07-23 19:36     ` Mathieu Poirier [this message]
2020-07-24  1:17       ` Tingwei Zhang
2020-07-17  5:45 ` [PATCH v3 20/20] coresight: allow the coresight core driver to be built as a module Tingwei Zhang

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