[DTrace-devel] [PATCH v2 03/12] Overhaul the stackdepth value test

[Kris Van Hees]

Woops, Houston, we have a problem...

And for two other patches that use the same FBT probe...)

__vfs_write doesn't seem like a stable function to use.  E.g. my 5.13.0 kernel
does not have it.

You will have to use a more stable probe to use, especially for the stack()
trsts.  Which is really hard to do because you never know what the kernel
people will mess with next.

On Fri, Jun 11, 2021 at 04:01:48PM -0400, Kris Van Hees wrote:
> Reviewed-by: Kris Van Hees <kris.van.hees at oracle.com>
> 
> On Tue, Jun 08, 2021 at 05:54:22PM -0400, eugene.loh at oracle.com wrote:
> > From: Eugene Loh <eugene.loh at oracle.com>
> > 
> > This test checks the value of stackdepth by using stack() as a
> > consistency check.  Address the following shortcomings:
> > 
> > 1) The test fires in BEGIN, which no longer has a kernel stack.
> > 
> > 2) The test incorrectly counts stack frames.
> > 
> > 3) The test passes because neither stack() nor stackdepth is implemented!
> > (Currently, stack() always reports nothing and stackdepth always 0.)
> > 
> > 4) An ERROR in the D script would cause the test to hang.
> > 
> > The corrected test will XFAIL until stack() and stackdepth are implemented.
> > 
> > Signed-off-by: Eugene Loh <eugene.loh at oracle.com>
> > ---
> >  test/unittest/stackdepth/tst.value.d   | 14 +++++++++++++-
> >  test/unittest/stackdepth/tst.value.r.p |  8 +++++---
> >  2 files changed, 18 insertions(+), 4 deletions(-)
> > 
> > diff --git a/test/unittest/stackdepth/tst.value.d b/test/unittest/stackdepth/tst.value.d
> > index 857728bd..a729bd3f 100644
> > --- a/test/unittest/stackdepth/tst.value.d
> > +++ b/test/unittest/stackdepth/tst.value.d
> > @@ -1,10 +1,12 @@
> >  /*
> >   * Oracle Linux DTrace.
> > - * Copyright (c) 2006, 2020, Oracle and/or its affiliates. All rights reserved.
> > + * Copyright (c) 2006, 2021, Oracle and/or its affiliates. All rights reserved.
> >   * Licensed under the Universal Permissive License v 1.0 as shown at
> >   * http://oss.oracle.com/licenses/upl.
> >   */
> > +/* @@xfail: dtv2 */
> >  
> > +#pragma D option destructive
> >  #pragma D option quiet
> >  
> >  /*
> > @@ -16,6 +18,11 @@
> >   */
> >  
> >  BEGIN
> > +{
> > +	system("echo write something > /dev/null");
> > +}
> > +
> > +fbt::__vfs_write:entry
> >  {
> >  	printf("DEPTH %d\n", stackdepth);
> >  	printf("TRACE BEGIN\n");
> > @@ -23,3 +30,8 @@ BEGIN
> >  	printf("TRACE END\n");
> >  	exit(0);
> >  }
> > +
> > +ERROR
> > +{
> > +	exit(1);
> > +}
> > diff --git a/test/unittest/stackdepth/tst.value.r.p b/test/unittest/stackdepth/tst.value.r.p
> > index d5143e38..9b071181 100755
> > --- a/test/unittest/stackdepth/tst.value.r.p
> > +++ b/test/unittest/stackdepth/tst.value.r.p
> > @@ -1,6 +1,6 @@
> >  #!/usr/bin/gawk -f
> >  # Oracle Linux DTrace.
> > -# Copyright (c) 2016, 2020, Oracle and/or its affiliates. All rights reserved.
> > +# Copyright (c) 2016, 2021, Oracle and/or its affiliates. All rights reserved.
> >  # Licensed under the Universal Permissive License v 1.0 as shown at
> >  # http://oss.oracle.com/licenses/upl.
> >  
> > @@ -12,12 +12,12 @@
> >  	getline;
> >  	count = 0;
> >  	while ($0 !~ /^TRACE END/) {
> > +		if (NF)
> > +			count++;
> >  		if (getline != 1) {
> >  			print "EOF or error while processing stack\n";
> >  			exit 0;
> >  		}
> > -		if (NF)
> > -			count++;
> >  	}
> >  }
> >  
> > @@ -26,6 +26,8 @@ END {
> >  		printf "Stack depth too large (%d > %d)\n", depth, count;
> >  	else if (count > depth)
> >  		printf "Stack depth too small (%d < %d)\n", depth, count;
> > +	else if (count == 0)
> > +		printf "Stack depth is 0\n";
> >  	else
> >  		printf "Stack depth OK\n";
> >  }
> > -- 
> > 2.18.4
> > 
> > 
> > _______________________________________________
> > DTrace-devel mailing list
> > DTrace-devel at oss.oracle.com
> > https://oss.oracle.com/mailman/listinfo/dtrace-devel
> 
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