From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-media@vger.kernel.org, linux-arm-msm@vger.kernel.org,
linux-btrfs@vger.kernel.org, linux-acpi@vger.kernel.org,
netdev@vger.kernel.org, Joe Perches <joe@perches.com>,
Jason Baron <jbaron@akamai.com>, Jonathan Corbet <corbet@lwn.net>
Subject: Re: [PATCH v3 1/7] Documentation: dynamic-debug: Add description of level bitmask
Date: Wed, 10 Jun 2020 14:26:41 +0200 [thread overview]
Message-ID: <20200610122641.GB1900758@kroah.com> (raw)
In-Reply-To: <0830ba57-d416-4788-351a-6d1b2ca5b7d8@linaro.org>
On Wed, Jun 10, 2020 at 01:29:20PM +0300, Stanimir Varbanov wrote:
> Hi Greg,
>
> On 6/9/20 2:16 PM, Greg Kroah-Hartman wrote:
> > On Tue, Jun 09, 2020 at 01:45:58PM +0300, Stanimir Varbanov wrote:
> >> This adds description of the level bitmask feature.
> >>
> >> Cc: Jonathan Corbet <corbet@lwn.net> (maintainer:DOCUMENTATION)
> >>
> >> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
> >> ---
> >> Documentation/admin-guide/dynamic-debug-howto.rst | 10 ++++++++++
> >> 1 file changed, 10 insertions(+)
> >>
> >> diff --git a/Documentation/admin-guide/dynamic-debug-howto.rst b/Documentation/admin-guide/dynamic-debug-howto.rst
> >> index 0dc2eb8e44e5..c2b751fc8a17 100644
> >> --- a/Documentation/admin-guide/dynamic-debug-howto.rst
> >> +++ b/Documentation/admin-guide/dynamic-debug-howto.rst
> >> @@ -208,6 +208,12 @@ line
> >> line -1605 // the 1605 lines from line 1 to line 1605
> >> line 1600- // all lines from line 1600 to the end of the file
> >>
> >> +level
> >> + The given level will be a bitmask ANDed with the level of the each ``pr_debug()``
> >> + callsite. This will allow to group debug messages and show only those of the
> >> + same level. The -p flag takes precedence over the given level. Note that we can
> >> + have up to five groups of debug messages.
> >
> > As was pointed out, this isn't a "level", it's some arbitrary type of
> > "grouping".
>
> Yes, it is grouping of KERN_DEBUG level messages by importance (my
> fault, I put incorrect name). What is important is driver author
> decision. Usually when the driver is huge and has a lot of debug
> messages it is not practical to enable all of them to chasing a
> particular bug or issue. You know that debugging (printk) add delays
> which could hide or rise additional issue(s) which would complicate
> debug and waste time.
That is why it is possible to turn on and off debugging messages on a
function/line basis already. Why not just use that instead?
> For the Venus driver I have defined three groups of KERN_DEBUG - low,
> medium and high (again the driver author(s) will decide what the
> importance is depending on his past experience).
>
> There is another point where the debugging is made by person who is not
> familiar with the driver code. In that case he/she cannot enable lines
> or range of lines because he don't know the details. Here the grouping
> by importance could help.
And they will really know what "low/medium/high" are?
Anyway, that makes a bit more sense, but the documentation could use a
lot more in order to describe this type of behavior, and what is
expected by both driver authors, and users of the interface.
thanks,
greg k-h
next prev parent reply other threads:[~2020-06-10 12:26 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-09 10:45 [PATCH v3 0/7] Venus dynamic debug Stanimir Varbanov
2020-06-09 10:45 ` [PATCH v3 1/7] Documentation: dynamic-debug: Add description of level bitmask Stanimir Varbanov
2020-06-09 11:09 ` Matthew Wilcox
2020-06-09 11:16 ` Greg Kroah-Hartman
2020-06-09 16:58 ` Joe Perches
2020-06-09 17:42 ` Edward Cree
2020-06-09 17:56 ` Joe Perches
2020-06-09 18:08 ` Edward Cree
2020-06-10 6:31 ` Greg Kroah-Hartman
2020-06-10 6:35 ` Joe Perches
2020-06-10 7:09 ` Greg Kroah-Hartman
2020-06-10 7:24 ` Joe Perches
2020-06-10 10:29 ` Stanimir Varbanov
2020-06-10 12:26 ` Greg Kroah-Hartman [this message]
2020-06-09 10:45 ` [PATCH v3 2/7] dynamic_debug: Group debug messages by " Stanimir Varbanov
2020-06-09 12:27 ` Petr Mladek
2020-06-09 10:46 ` [PATCH v3 3/7] dev_printk: Add dev_dbg_level macro over dynamic one Stanimir Varbanov
2020-06-09 10:46 ` [PATCH v3 4/7] printk: Add pr_debug_level " Stanimir Varbanov
2020-06-09 11:12 ` Greg Kroah-Hartman
2020-06-09 10:46 ` [PATCH v3 5/7] venus: Add debugfs interface to set firmware log level Stanimir Varbanov
2020-06-09 11:12 ` Greg Kroah-Hartman
2020-06-11 11:51 ` Stanimir Varbanov
2020-06-09 10:46 ` [PATCH v3 6/7] venus: Make debug infrastructure more flexible Stanimir Varbanov
2020-06-09 11:14 ` Greg Kroah-Hartman
2020-06-10 13:29 ` Stanimir Varbanov
2020-06-10 13:37 ` Greg Kroah-Hartman
2020-06-10 19:49 ` Joe Perches
2020-06-10 20:23 ` Joe Perches
2020-06-11 6:26 ` Greg Kroah-Hartman
2020-06-11 6:42 ` Joe Perches
2020-06-11 10:52 ` Daniel Thompson
2020-06-11 11:31 ` Stanimir Varbanov
2020-06-11 12:18 ` Daniel Thompson
2020-06-11 21:19 ` jim.cromie
2020-06-11 21:59 ` Jason Baron
2020-06-11 22:33 ` Joe Perches
2020-06-12 0:08 ` jim.cromie
2020-06-10 18:32 ` WIP generic module->debug_flags and dynamic_debug jim.cromie
2020-06-10 20:24 ` Joe Perches
2020-06-11 11:26 ` Rasmus Villemoes
2020-06-11 14:09 ` jim.cromie
2020-06-09 10:46 ` [PATCH v3 7/7] venus: Add a debugfs file for SSR trigger Stanimir Varbanov
2020-06-09 11:13 ` [PATCH v3 0/7] Venus dynamic debug Matthew Wilcox
2020-06-09 16:03 ` Randy Dunlap
2020-06-09 16:49 ` Joe Perches
2020-06-09 21:21 ` jim.cromie
2020-06-09 22:23 ` Joe Perches
2020-06-10 1:58 ` Joe Perches
2020-06-10 3:10 ` jim.cromie
2020-06-09 16:40 ` Joe Perches
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