[PATCH] remove unimplemented syscalls noise

[PATCH] remove unimplemented syscalls noise

[Kyle McMartin]

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Hi guys, this is a simple patch which removes the really
irritating sc<> messages that appear in logs. I haven't seen
any reason to keep the messages, as they appear to be
superfluous since the fact that some processes spit it doesn't
effect their operation.

Regards,
--
Kyle McMartin <kyle@engsoc.carleton.ca>
System Administrator, The EngSoc Project
Faculty of Engineering, Carleton University

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--- arch/ia64/kernel/traps.c.orig	2003-11-16 12:58:50.483531475 -0500
+++ arch/ia64/kernel/traps.c	2003-11-16 12:59:55.443491617 -0500
@@ -225,10 +225,6 @@
 		 unsigned long arg4, unsigned long arg5, unsigned long arg6, unsigned long arg7,
 		 unsigned long stack)
 {
-	struct pt_regs *regs = (struct pt_regs *) &stack;
-
-	printk(KERN_DEBUG "%s(%d): <sc%ld(%lx,%lx,%lx,%lx)>\n", current->comm, current->pid,
-	       regs->r15, arg0, arg1, arg2, arg3);
 	return -ENOSYS;
 }
 

Re: [PATCH] remove unimplemented syscalls noise

[David Mosberger]

>>>>> On Wed, 19 Nov 2003 11:42:16 -0500, Kyle McMartin <kyle@engsoc.carleton.ca> said:

  Kyle> Hi guys, this is a simple patch which removes the really
  Kyle> irritating sc<> messages that appear in logs.

What's wrong with dmesg -n4?  Those messages are marked KERN_DEBUG for
a reason.  BTW: Red Hat does this by default, but Debian doesn't.  In
my opinion, Red Hat does the right thing here: by default, most user's
don't care about such messages, but they're invaluable when tracking
down problems.

	--david

Re: [PATCH] remove unimplemented syscalls noise

[Matthew Wilcox]

On Wed, Nov 19, 2003 at 11:44:46AM -0800, David Mosberger wrote:
> What's wrong with dmesg -n4?  Those messages are marked KERN_DEBUG for
> a reason.  BTW: Red Hat does this by default, but Debian doesn't.  In
> my opinion, Red Hat does the right thing here: by default, most user's
> don't care about such messages, but they're invaluable when tracking
> down problems.

This is the same thing as printing the user unaligned exceptions.
It's something no other architecture does, and for a reason, which has
been explained to you before, but you don't want to fix it.  *sigh*.

-- 
"It's not Hollywood.  War is real, war is primarily not about defeat or
victory, it is about death.  I've seen thousands and thousands of dead bodies.
Do you think I want to have an academic debate on this subject?" -- Robert Fisk

Re: [PATCH] remove unimplemented syscalls noise

[David Mosberger]

>>>>> On Wed, 19 Nov 2003 19:54:02 +0000, Matthew Wilcox <willy@debian.org> said:

  Matthew> This is the same thing as printing the user unaligned
  Matthew> exceptions.  It's something no other architecture does, and
  Matthew> for a reason, which has been explained to you before, but
  Matthew> you don't want to fix it.

And yet both features are incredibly useful when debugging, something
you seem to ignore.

The printk-level is there for a _reason_.  Why not use it?

	--david

RE: [PATCH] remove unimplemented syscalls noise

[Seth, Rohit]

Well, in the case of unaligned faults, there is no other way for an
application to know that there were unaligned faults.  Whereas for
unsupported system calls, the kernel will return ENOSYS and thus the
application gets the required notification (so that it can take any
action it wants).  It does not need to depend on dmesg stuff to find
that information out.  

So, it does make sense to remove this printk (even though it is _debug_)
in this path.

> -----Original Message-----
> From: linux-ia64-owner@vger.kernel.org [mailto:linux-ia64-
> owner@vger.kernel.org] On Behalf Of Matthew Wilcox
> Sent: Wednesday, November 19, 2003 11:54 AM
> To: davidm@hpl.hp.com
> Cc: Kyle McMartin; linux-ia64@vger.kernel.org
> Subject: Re: [PATCH] remove unimplemented syscalls noise
> 
> On Wed, Nov 19, 2003 at 11:44:46AM -0800, David Mosberger wrote:
> > What's wrong with dmesg -n4?  Those messages are marked KERN_DEBUG
for
> > a reason.  BTW: Red Hat does this by default, but Debian doesn't.
In
> > my opinion, Red Hat does the right thing here: by default, most
user's
> > don't care about such messages, but they're invaluable when tracking
> > down problems.
> 
> This is the same thing as printing the user unaligned exceptions.
> It's something no other architecture does, and for a reason, which has
> been explained to you before, but you don't want to fix it.  *sigh*.
> 
> --
> "It's not Hollywood.  War is real, war is primarily not about defeat
or
> victory, it is about death.  I've seen thousands and thousands of dead
> bodies.
> Do you think I want to have an academic debate on this subject?" --
Robert
> Fisk
> -
> To unsubscribe from this list: send the line "unsubscribe linux-ia64"
in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH] remove unimplemented syscalls noise

[Matthew Wilcox]

On Wed, Nov 19, 2003 at 12:11:03PM -0800, David Mosberger wrote:
> >>>>> On Wed, 19 Nov 2003 19:54:02 +0000, Matthew Wilcox <willy@debian.org> said:
> 
>   Matthew> This is the same thing as printing the user unaligned
>   Matthew> exceptions.  It's something no other architecture does, and
>   Matthew> for a reason, which has been explained to you before, but
>   Matthew> you don't want to fix it.
> 
> And yet both features are incredibly useful when debugging, something
> you seem to ignore.

No, it *isn't*.  The majority of systems in use are not being debugged
(regardless of how you & I spend most of our time).  Having these
messages constantly stream past in dmesg (which no other architecture
does) serves only to potentially mask other, useful pieces of information
and confuse the customer.

Every time we emit something to the system log, it's a potential support
call.  Our friends in other parts of HP are already unhappy with how much
output Linux produces even when everything's OK.  It's also a sysadmin
hassle as logfiles fill up more quickly when this kind of junk goes by.

I'm sure this was useful for debugging once, but those days are gone.
We need to print less of this stuff.  Something a lot of places do is:

#undef DEBUG

#ifdef DEBUG
#define DBG(x...) printk(x)
#else
#define DBG(x...)
#endif

Would it mollify you if these printks were turned into DBGs?

Or perhaps better, we could use pr_debug() from <linux/kernel.h>.

-- 
"It's not Hollywood.  War is real, war is primarily not about defeat or
victory, it is about death.  I've seen thousands and thousands of dead bodies.
Do you think I want to have an academic debate on this subject?" -- Robert Fisk

RE: [PATCH] remove unimplemented syscalls noise

[David Mosberger]

>>>>> On Wed, 19 Nov 2003 12:15:23 -0800, "Seth, Rohit" <rohit.seth@intel.com> said:

  Rohit> Well, in the case of unaligned faults, there is no other way
  Rohit> for an application to know that there were unaligned faults.
  Rohit> Whereas for unsupported system calls, the kernel will return
  Rohit> ENOSYS and thus the application gets the required
  Rohit> notification (so that it can take any action it wants).  It
  Rohit> does not need to depend on dmesg stuff to find that
  Rohit> information out.

True in principle, but in practice, you can't always run strace to
find out what's going on, either because the problem starts in early
boot or because the problem is triggered indirectly through daemons
etc.

  Rohit> So, it does make sense to remove this printk (even though it
  Rohit> is _debug_) in this path.

I really much favor for distro's to make dmesg -n4 the default.  There
is no reason to bother average users with KERN_{NOTICE,INFO,DEBUG}
stuff unless they ask for it.

	--david

Re: [PATCH] remove unimplemented syscalls noise

[David Mosberger]

>>>>> On Wed, 19 Nov 2003 20:20:20 +0000, Matthew Wilcox <willy@debian.org> said:

  >>  And yet both features are incredibly useful when debugging,
  >> something you seem to ignore.

  Matthew> No, it *isn't*.  The majority of systems in use are not
  Matthew> being debugged (regardless of how you & I spend most of our
  Matthew> time).

Please read my sentence: it's incredibly useful when _debugging_ a
problem.

Nobody suggests to print those messages for normal users.  dmesg -n4
will take care of them for good.

  Matthew> Every time we emit something to the system log, it's a
  Matthew> potential support call.  Our friends in other parts of HP
  Matthew> are already unhappy with how much output Linux produces
  Matthew> even when everything's OK.  It's also a sysadmin hassle as
  Matthew> logfiles fill up more quickly when this kind of junk goes
  Matthew> by.

Can I say dmesg -n4??

  Matthew> I'm sure this was useful for debugging once, but those days
  Matthew> are gone.  We need to print less of this stuff.  Something
  Matthew> a lot of places do is:

  Matthew> #undef DEBUG

  Matthew> #ifdef DEBUG #define DBG(x...) printk(x) #else #define
  Matthew> DBG(x...)  #endif

  Matthew> Would it mollify you if these printks were turned into
  Matthew> DBGs?

Nope.  dmesg -n4 is adequate.

	--david

Re: [PATCH] remove unimplemented syscalls noise

[Matthew Wilcox]

On Wed, Nov 19, 2003 at 12:33:17PM -0800, David Mosberger wrote:
>   Matthew> Every time we emit something to the system log, it's a
>   Matthew> potential support call.  Our friends in other parts of HP
>   Matthew> are already unhappy with how much output Linux produces
>   Matthew> even when everything's OK.  It's also a sysadmin hassle as
>   Matthew> logfiles fill up more quickly when this kind of junk goes
>   Matthew> by.
> 
> Can I say dmesg -n4??

No, you can't.  Users check their logfiles.

-- 
"It's not Hollywood.  War is real, war is primarily not about defeat or
victory, it is about death.  I've seen thousands and thousands of dead bodies.
Do you think I want to have an academic debate on this subject?" -- Robert Fisk

Re: [PATCH] remove unimplemented syscalls noise

[Rich Altmaier]

I don't have an answer here, but some perspective to offer.
Over the years we have found that customers will react to
any message in the SYSLOG file.  That is, you get the least
grief by having messages appear there when you want the
customer/administrator to take an action.  If they are not
to take an action, then don't show the message.

For debugging, we have used schemes which don't raise the
debug data to the "normal system administration" procedures.
Such as a private kernel logging buffer, dumped together with
a kernel core dump, or viewable by a kernel debugger if you
know where to look, etc.  But not part of normal documented
system admin procedures.

Of course for debugging we like good data...
FYI, Rich

Re: [PATCH] remove unimplemented syscalls noise

[David Mosberger]

>>>>> On Wed, 19 Nov 2003 20:35:51 +0000, Matthew Wilcox <willy@debian.org> said:

  Matthew> On Wed, Nov 19, 2003 at 12:33:17PM -0800, David Mosberger
  Matthew> wrote: Every time we emit something to the system log, it's
  Matthew> a potential support call.  Our friends in other parts of HP
  Matthew> are already unhappy with how much output Linux produces
  Matthew> even when everything's OK.  It's also a sysadmin hassle as
  Matthew> logfiles fill up more quickly when this kind of junk goes
  Matthew> by.

  >>  Can I say dmesg -n4??

  Matthew> No, you can't.  Users check their logfiles.

syslog.conf?

I don't see how you can argue that debug/informational messages
_shouldn't_ be displayed/logged for ordinary users under normal
circumstances yet argue _for_ configuring syslog.conf to log precisely
such messages.

I'm quite certain there are countless other ways for user-space to
trigger lots of KERN_INFO/KERN_DEBUG messages.  See kernel/sysctl.c or
security/security.c, for example.

Having said that, I now realize that there is a problem:
ia64_ni_syscall() is/was intended for syscalls that were supposed to
be implemented but were missing for some reason.  Everything else
should be handled by sys_ni_syscall.  There are no such syscalls
anymore, so I think what we should do is change entry.S from using
ia64_ni_syscall to sys_ni_syscall (and if there are no callers of
ia64_ni_syscall left, delete it).  Want to send a patch?

	--david

Re: [PATCH] remove unimplemented syscalls noise

[David Mosberger]

>>>>> On Wed, 19 Nov 2003 13:21:07 -0800, David Mosberger <davidm@linux.hpl.hp.com> said:

  >> Having said that, I now realize that there is a problem:
  >> ia64_ni_syscall() is/was intended for syscalls that were supposed
  >> to be implemented but were missing for some reason.  Everything
  >> else should be handled by sys_ni_syscall.  There are no such
  >> syscalls anymore, so I think what we should do is change entry.S
  >> from using ia64_ni_syscall to sys_ni_syscall (and if there are no
  >> callers of ia64_ni_syscall left, delete it).  Want to send a
  >> patch?

Actually, in the interest of keeping the patch small, it's better to
remove the printk message in ia64_ni_syscall() for 2.6.0 and then we
can do the proper cleanup for 2.6.1.

	--david

Re: [PATCH] remove unimplemented syscalls noise

[Matthias Fouquet-Lapar]

> Please read my sentence: it's incredibly useful when _debugging_ a
> problem.

I guess I agree that it is very useful for debugging. But maybe
a different mechanism could be used. Instead of sending this to
the general SYSLOG, why not use a signal (default being off).
This would help interested users to catch the exception in the
execution context.

If a user is debugging a problem, he can simply install a signal
handler

Thanks

Matthias Fouquet-Lapar  Core Platform Software    mfl@sgi.com  VNET 521-8213
Principal Engineer      Silicon Graphics          Home Office (+33) 1 3047 4127