diff mbox

[re:,v2,00/15,-,05/11] dyndbg: change +T:name_terminator to dot

Message ID 7cb5c8b6c6efba7e437595266638be39f23361fc.1701993656.git.jim.cromie@gmail.com
State New
Headers

Commit Message

Jim Cromie Dec. 8, 2023, 12:15 a.m. UTC 
  This replaces ',' with '.' as the char that ends the +T:name.

This allows a later patch to treat ',' as a space, which mostly
eliminates the need to quote query/rules.  And this in turn avoids
quoting hassles:

  modprobe test_dynamic_debug dyndbg=class,D2_CORE,+p

It is particularly good for passing boot-args into test-scripts.

  vng -p 4 -v \
  -a test_dynamic_debug.dyndbg=class,D2_CORE,+p

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
 lib/dynamic_debug.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Petr Mladek Dec. 18, 2023, 5:29 p.m. UTC | #1 
On Thu 2023-12-07 17:15:08, Jim Cromie wrote:
> This replaces ',' with '.' as the char that ends the +T:name.
> 
> This allows a later patch to treat ',' as a space, which mostly
> eliminates the need to quote query/rules.  And this in turn avoids
> quoting hassles:
> 
>   modprobe test_dynamic_debug dyndbg=class,D2_CORE,+p
> 
> It is particularly good for passing boot-args into test-scripts.
> 
>   vng -p 4 -v \
>   -a test_dynamic_debug.dyndbg=class,D2_CORE,+p

Could you please add example how it looked before and after?
Is this format documented somewhere?
Will the documentation get updated?
Could it break existing scripts? [*]

The dynamic debug interface is really hard to use for me
as an occasional user. I always have to look into
Documentation/admin-guide/dynamic-debug-howto.rst

Anyway, there should be a good reason to change the interface.
And the exaplantion:

   "Let's use '.' instead of ',' so that we could later
    treat ',' as space"

sounds scarry. It does not explain what is the advantage at all.


[*] Some scripts are using the interface even in the mainline,
for example:

$> git grep "dynamic_debug" tools/testing/
tools/testing/selftests/bpf/test_tunnel.sh:     echo 'file ip_gre.c +p' > /sys/kernel/debug/dynamic_debug/control
tools/testing/selftests/bpf/test_tunnel.sh:     echo 'file ip6_gre.c +p' > /sys/kernel/debug/dynamic_debug/control
tools/testing/selftests/bpf/test_tunnel.sh:     echo 'file geneve.c +p' > /sys/kernel/debug/dynamic_debug/control
tools/testing/selftests/bpf/test_tunnel.sh:     echo 'file ipip.c +p' > /sys/kernel/debug/dynamic_debug/control
tools/testing/selftests/livepatch/functions.sh: DYNAMIC_DEBUG=$(grep '^kernel/livepatch' /sys/kernel/debug/dynamic_debug/control | \
tools/testing/selftests/livepatch/functions.sh:         echo -n "$DYNAMIC_DEBUG" > /sys/kernel/debug/dynamic_debug/control
tools/testing/selftests/livepatch/functions.sh:function set_dynamic_debug() {
tools/testing/selftests/livepatch/functions.sh:        cat <<-EOF > /sys/kernel/debug/dynamic_debug/control
tools/testing/selftests/livepatch/functions.sh: set_dynamic_debug


Best Regards,
Petr
Łukasz Bartosik Dec. 21, 2023, 3:21 p.m. UTC | #2 
pon., 18 gru 2023 o 18:29 Petr Mladek <pmladek@suse.com> napisał(a):
>
> On Thu 2023-12-07 17:15:08, Jim Cromie wrote:
> > This replaces ',' with '.' as the char that ends the +T:name.
> >
> > This allows a later patch to treat ',' as a space, which mostly
> > eliminates the need to quote query/rules.  And this in turn avoids
> > quoting hassles:
> >
> >   modprobe test_dynamic_debug dyndbg=class,D2_CORE,+p
> >
> > It is particularly good for passing boot-args into test-scripts.
> >
> >   vng -p 4 -v \
> >   -a test_dynamic_debug.dyndbg=class,D2_CORE,+p
>
> Could you please add example how it looked before and after?

Before a user had to issue a command in the format
modprobe test_dynamic_debug dyndbg="class D2_CORE +p"

Now a use can use either
modprobe test_dynamic_debug dyndbg="class D2_CORE +p"
or
modprobe test_dynamic_debug dyndbg=class,D2_CORE,+p

> Is this format documented somewhere?
> Will the documentation get updated?

Documentation will be updated.

> Could it break existing scripts? [*]
>

It should not break any scripts as this change does not change the
interface but extends it.

> The dynamic debug interface is really hard to use for me
> as an occasional user. I always have to look into
> Documentation/admin-guide/dynamic-debug-howto.rst
>
> Anyway, there should be a good reason to change the interface.
> And the exaplantion:
>
>    "Let's use '.' instead of ',' so that we could later
>     treat ',' as space"
>
> sounds scarry. It does not explain what is the advantage at all.
>

I will clarify in the commit message that this change allows to use
two formats either
modprobe test_dynamic_debug dyndbg="class D2_CORE +p"
or
modprobe test_dynamic_debug dyndbg=class,D2_CORE,+p

>
> [*] Some scripts are using the interface even in the mainline,
> for example:
>
> $> git grep "dynamic_debug" tools/testing/
> tools/testing/selftests/bpf/test_tunnel.sh:     echo 'file ip_gre.c +p' > /sys/kernel/debug/dynamic_debug/control
> tools/testing/selftests/bpf/test_tunnel.sh:     echo 'file ip6_gre.c +p' > /sys/kernel/debug/dynamic_debug/control
> tools/testing/selftests/bpf/test_tunnel.sh:     echo 'file geneve.c +p' > /sys/kernel/debug/dynamic_debug/control
> tools/testing/selftests/bpf/test_tunnel.sh:     echo 'file ipip.c +p' > /sys/kernel/debug/dynamic_debug/control
> tools/testing/selftests/livepatch/functions.sh: DYNAMIC_DEBUG=$(grep '^kernel/livepatch' /sys/kernel/debug/dynamic_debug/control | \
> tools/testing/selftests/livepatch/functions.sh:         echo -n "$DYNAMIC_DEBUG" > /sys/kernel/debug/dynamic_debug/control
> tools/testing/selftests/livepatch/functions.sh:function set_dynamic_debug() {
> tools/testing/selftests/livepatch/functions.sh:        cat <<-EOF > /sys/kernel/debug/dynamic_debug/control
> tools/testing/selftests/livepatch/functions.sh: set_dynamic_debug
>

Good to know. I will use these scripts to make sure the dynamic debug
interface is not broken.

Thanks,
Lukasz

>
> Best Regards,
> Petr
Petr Mladek Jan. 4, 2024, 7:54 a.m. UTC | #3 
On Thu 2023-12-21 16:21:49, Łukasz Bartosik wrote:
> pon., 18 gru 2023 o 18:29 Petr Mladek <pmladek@suse.com> napisał(a):
> >
> > On Thu 2023-12-07 17:15:08, Jim Cromie wrote:
> > > This replaces ',' with '.' as the char that ends the +T:name.
> > >
> > > This allows a later patch to treat ',' as a space, which mostly
> > > eliminates the need to quote query/rules.  And this in turn avoids
> > > quoting hassles:
> > >
> > >   modprobe test_dynamic_debug dyndbg=class,D2_CORE,+p
> > >
> > > It is particularly good for passing boot-args into test-scripts.
> > >
> > >   vng -p 4 -v \
> > >   -a test_dynamic_debug.dyndbg=class,D2_CORE,+p
> >
> > Could you please add example how it looked before and after?
> 
> Before a user had to issue a command in the format
> modprobe test_dynamic_debug dyndbg="class D2_CORE +p"
> 
> Now a use can use either
> modprobe test_dynamic_debug dyndbg="class D2_CORE +p"
> or
> modprobe test_dynamic_debug dyndbg=class,D2_CORE,+p

I see. This was not clear to me. Please, mention it in
the commit message.

That said, I am not sure if it is worth it and if it
is a good idea. Supporting more formats adds complexity
and confusion. It is the reason why people hate perl.

I agree that quoting in scripts is complicated. Well,
a sane approach is to use quotes everywhere where possible.

If a script works correctly only with class,D2_CORE,+p
and breaks with "class D2_CORE +p" then it is a ticking
bomb. People might try to use "class D2_CORE +p"
one day because they would cut&paste the string
from the internet.

> > Is this format documented somewhere?
> > Will the documentation get updated?
> 
> Documentation will be updated.
> 
> > Could it break existing scripts? [*]
> 
> It should not break any scripts as this change does not change the
> interface but extends it.
> 
> > The dynamic debug interface is really hard to use for me
> > as an occasional user. I always have to look into
> > Documentation/admin-guide/dynamic-debug-howto.rst
> >
> > Anyway, there should be a good reason to change the interface.
> > And the exaplantion:
> >
> >    "Let's use '.' instead of ',' so that we could later
> >     treat ',' as space"
> >
> > sounds scarry. It does not explain what is the advantage at all.
> >
> I will clarify in the commit message that this change allows to use
> two formats either
> modprobe test_dynamic_debug dyndbg="class D2_CORE +p"
> or
> modprobe test_dynamic_debug dyndbg=class,D2_CORE,+p

But the patch replaces ',' with '.'. It looks like it modifies
some existing syntax.

Note that I am not familiar with this code. And I even do not see
the patched function in the current Linus' tree.

Best Regards,
Petr
Łukasz Bartosik Jan. 8, 2024, 12:21 p.m. UTC | #4 
czw., 4 sty 2024 o 08:54 Petr Mladek <pmladek@suse.com> napisał(a):
>
> On Thu 2023-12-21 16:21:49, Łukasz Bartosik wrote:
> > pon., 18 gru 2023 o 18:29 Petr Mladek <pmladek@suse.com> napisał(a):
> > >
> > > On Thu 2023-12-07 17:15:08, Jim Cromie wrote:
> > > > This replaces ',' with '.' as the char that ends the +T:name.
> > > >
> > > > This allows a later patch to treat ',' as a space, which mostly
> > > > eliminates the need to quote query/rules.  And this in turn avoids
> > > > quoting hassles:
> > > >
> > > >   modprobe test_dynamic_debug dyndbg=class,D2_CORE,+p
> > > >
> > > > It is particularly good for passing boot-args into test-scripts.
> > > >
> > > >   vng -p 4 -v \
> > > >   -a test_dynamic_debug.dyndbg=class,D2_CORE,+p
> > >
> > > Could you please add example how it looked before and after?
> >
> > Before a user had to issue a command in the format
> > modprobe test_dynamic_debug dyndbg="class D2_CORE +p"
> >
> > Now a use can use either
> > modprobe test_dynamic_debug dyndbg="class D2_CORE +p"
> > or
> > modprobe test_dynamic_debug dyndbg=class,D2_CORE,+p
>
> I see. This was not clear to me. Please, mention it in
> the commit message.
>

In the patchset v3 I squashed "dyndbg: change +T:name_terminator to
dot" with "dyndbg: add processing of T(race) flag argument" but I will
clarify this topic in the "dyndbg: treat comma as a token separator"

> That said, I am not sure if it is worth it and if it
> is a good idea. Supporting more formats adds complexity
> and confusion. It is the reason why people hate perl.
>
> I agree that quoting in scripts is complicated. Well,
> a sane approach is to use quotes everywhere where possible.
>
> If a script works correctly only with class,D2_CORE,+p
> and breaks with "class D2_CORE +p" then it is a ticking
> bomb. People might try to use "class D2_CORE +p"
> one day because they would cut&paste the string
> from the internet.
>

Addition of new format of dynamic debug queries does not obsolete the
existing format.

> > > Is this format documented somewhere?
> > > Will the documentation get updated?
> >
> > Documentation will be updated.
> >
> > > Could it break existing scripts? [*]
> >
> > It should not break any scripts as this change does not change the
> > interface but extends it.
> >
> > > The dynamic debug interface is really hard to use for me
> > > as an occasional user. I always have to look into
> > > Documentation/admin-guide/dynamic-debug-howto.rst
> > >
> > > Anyway, there should be a good reason to change the interface.
> > > And the exaplantion:
> > >
> > >    "Let's use '.' instead of ',' so that we could later
> > >     treat ',' as space"
> > >
> > > sounds scarry. It does not explain what is the advantage at all.
> > >
> > I will clarify in the commit message that this change allows to use
> > two formats either
> > modprobe test_dynamic_debug dyndbg="class D2_CORE +p"
> > or
> > modprobe test_dynamic_debug dyndbg=class,D2_CORE,+p
>
> But the patch replaces ',' with '.'. It looks like it modifies
> some existing syntax.
>
> Note that I am not familiar with this code. And I even do not see
> the patched function in the current Linus' tree.
>

Next patchset will include updated dynamic debug documentation.
Hopefully this will help to resolve doubts.

Regards,
Lukasz

> Best Regards,
> Petr
>
diff mbox

Patch

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 2ac1bd7f105f..a5fc80edd24c 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -172,7 +172,7 @@  char *read_T_args(const char *str, struct flag_settings *modifiers)
 	}
 
 	str += 2;
-	end = strchr(str, ',');
+	end = strchr(str, '.');
 	if (end && *(end + 1) == '\0')
 		return NULL;
 
@@ -264,7 +264,7 @@  static char *ddebug_describe_ctrl(struct dd_ctrl *ctrl, struct ctrlbuf *cb)
 	for (i = 0; i < ARRAY_SIZE(opt_array); ++i)
 		if (ctrl->flags & opt_array[i].flag) {
 			if (show_args)
-				*p++ = ',';
+				*p++ = '.';
 			*p++ = opt_array[i].opt_char;
 			show_args = opt_array[i].show_args;
 			if (show_args)